LCOV - code coverage report
Current view: top level - lib - assoc_array.c (source / functions) Hit Total Coverage
Test: gcov_data_raspi2_real_modules_combined.info Lines: 122 591 20.6 %
Date: 2020-09-30 20:25:40 Functions: 12 18 66.7 %
Branches: 67 394 17.0 %

           Branch data     Line data    Source code
       1                 :            : // SPDX-License-Identifier: GPL-2.0-or-later
       2                 :            : /* Generic associative array implementation.
       3                 :            :  *
       4                 :            :  * See Documentation/core-api/assoc_array.rst for information.
       5                 :            :  *
       6                 :            :  * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
       7                 :            :  * Written by David Howells (dhowells@redhat.com)
       8                 :            :  */
       9                 :            : //#define DEBUG
      10                 :            : #include <linux/rcupdate.h>
      11                 :            : #include <linux/slab.h>
      12                 :            : #include <linux/err.h>
      13                 :            : #include <linux/assoc_array_priv.h>
      14                 :            : 
      15                 :            : /*
      16                 :            :  * Iterate over an associative array.  The caller must hold the RCU read lock
      17                 :            :  * or better.
      18                 :            :  */
      19                 :        207 : static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
      20                 :            :                                        const struct assoc_array_ptr *stop,
      21                 :            :                                        int (*iterator)(const void *leaf,
      22                 :            :                                                        void *iterator_data),
      23                 :            :                                        void *iterator_data)
      24                 :            : {
      25                 :            :         const struct assoc_array_shortcut *shortcut;
      26                 :            :         const struct assoc_array_node *node;
      27                 :            :         const struct assoc_array_ptr *cursor, *ptr, *parent;
      28                 :            :         unsigned long has_meta;
      29                 :            :         int slot, ret;
      30                 :            : 
      31                 :            :         cursor = root;
      32                 :            : 
      33                 :            : begin_node:
      34         [ -  + ]:        207 :         if (assoc_array_ptr_is_shortcut(cursor)) {
      35                 :            :                 /* Descend through a shortcut */
      36                 :            :                 shortcut = assoc_array_ptr_to_shortcut(cursor);
      37                 :          0 :                 cursor = READ_ONCE(shortcut->next_node); /* Address dependency. */
      38                 :            :         }
      39                 :            : 
      40                 :            :         node = assoc_array_ptr_to_node(cursor);
      41                 :            :         slot = 0;
      42                 :            : 
      43                 :            :         /* We perform two passes of each node.
      44                 :            :          *
      45                 :            :          * The first pass does all the leaves in this node.  This means we
      46                 :            :          * don't miss any leaves if the node is split up by insertion whilst
      47                 :            :          * we're iterating over the branches rooted here (we may, however, see
      48                 :            :          * some leaves twice).
      49                 :            :          */
      50                 :            :         has_meta = 0;
      51         [ +  - ]:        207 :         for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
      52                 :        414 :                 ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */
      53                 :        207 :                 has_meta |= (unsigned long)ptr;
      54   [ +  -  +  - ]:        414 :                 if (ptr && assoc_array_ptr_is_leaf(ptr)) {
      55                 :            :                         /* We need a barrier between the read of the pointer,
      56                 :            :                          * which is supplied by the above READ_ONCE().
      57                 :            :                          */
      58                 :            :                         /* Invoke the callback */
      59                 :        207 :                         ret = iterator(assoc_array_ptr_to_leaf(ptr),
      60                 :            :                                        iterator_data);
      61         [ +  - ]:        207 :                         if (ret)
      62                 :        207 :                                 return ret;
      63                 :            :                 }
      64                 :            :         }
      65                 :            : 
      66                 :            :         /* The second pass attends to all the metadata pointers.  If we follow
      67                 :            :          * one of these we may find that we don't come back here, but rather go
      68                 :            :          * back to a replacement node with the leaves in a different layout.
      69                 :            :          *
      70                 :            :          * We are guaranteed to make progress, however, as the slot number for
      71                 :            :          * a particular portion of the key space cannot change - and we
      72                 :            :          * continue at the back pointer + 1.
      73                 :            :          */
      74         [ #  # ]:          0 :         if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE))
      75                 :            :                 goto finished_node;
      76                 :            :         slot = 0;
      77                 :            : 
      78                 :            : continue_node:
      79                 :            :         node = assoc_array_ptr_to_node(cursor);
      80         [ #  # ]:          0 :         for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
      81                 :          0 :                 ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */
      82         [ #  # ]:          0 :                 if (assoc_array_ptr_is_meta(ptr)) {
      83                 :          0 :                         cursor = ptr;
      84                 :          0 :                         goto begin_node;
      85                 :            :                 }
      86                 :            :         }
      87                 :            : 
      88                 :            : finished_node:
      89                 :            :         /* Move up to the parent (may need to skip back over a shortcut) */
      90                 :          0 :         parent = READ_ONCE(node->back_pointer); /* Address dependency. */
      91                 :          0 :         slot = node->parent_slot;
      92         [ #  # ]:          0 :         if (parent == stop)
      93                 :            :                 return 0;
      94                 :            : 
      95         [ #  # ]:          0 :         if (assoc_array_ptr_is_shortcut(parent)) {
      96                 :            :                 shortcut = assoc_array_ptr_to_shortcut(parent);
      97                 :            :                 cursor = parent;
      98                 :          0 :                 parent = READ_ONCE(shortcut->back_pointer); /* Address dependency. */
      99                 :          0 :                 slot = shortcut->parent_slot;
     100         [ #  # ]:          0 :                 if (parent == stop)
     101                 :            :                         return 0;
     102                 :            :         }
     103                 :            : 
     104                 :            :         /* Ascend to next slot in parent node */
     105                 :            :         cursor = parent;
     106                 :          0 :         slot++;
     107                 :          0 :         goto continue_node;
     108                 :            : }
     109                 :            : 
     110                 :            : /**
     111                 :            :  * assoc_array_iterate - Pass all objects in the array to a callback
     112                 :            :  * @array: The array to iterate over.
     113                 :            :  * @iterator: The callback function.
     114                 :            :  * @iterator_data: Private data for the callback function.
     115                 :            :  *
     116                 :            :  * Iterate over all the objects in an associative array.  Each one will be
     117                 :            :  * presented to the iterator function.
     118                 :            :  *
     119                 :            :  * If the array is being modified concurrently with the iteration then it is
     120                 :            :  * possible that some objects in the array will be passed to the iterator
     121                 :            :  * callback more than once - though every object should be passed at least
     122                 :            :  * once.  If this is undesirable then the caller must lock against modification
     123                 :            :  * for the duration of this function.
     124                 :            :  *
     125                 :            :  * The function will return 0 if no objects were in the array or else it will
     126                 :            :  * return the result of the last iterator function called.  Iteration stops
     127                 :            :  * immediately if any call to the iteration function results in a non-zero
     128                 :            :  * return.
     129                 :            :  *
     130                 :            :  * The caller should hold the RCU read lock or better if concurrent
     131                 :            :  * modification is possible.
     132                 :            :  */
     133                 :        207 : int assoc_array_iterate(const struct assoc_array *array,
     134                 :            :                         int (*iterator)(const void *object,
     135                 :            :                                         void *iterator_data),
     136                 :            :                         void *iterator_data)
     137                 :            : {
     138                 :        207 :         struct assoc_array_ptr *root = READ_ONCE(array->root); /* Address dependency. */
     139                 :            : 
     140         [ +  - ]:        207 :         if (!root)
     141                 :            :                 return 0;
     142                 :        207 :         return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data);
     143                 :            : }
     144                 :            : 
     145                 :            : enum assoc_array_walk_status {
     146                 :            :         assoc_array_walk_tree_empty,
     147                 :            :         assoc_array_walk_found_terminal_node,
     148                 :            :         assoc_array_walk_found_wrong_shortcut,
     149                 :            : };
     150                 :            : 
     151                 :            : struct assoc_array_walk_result {
     152                 :            :         struct {
     153                 :            :                 struct assoc_array_node *node;  /* Node in which leaf might be found */
     154                 :            :                 int             level;
     155                 :            :                 int             slot;
     156                 :            :         } terminal_node;
     157                 :            :         struct {
     158                 :            :                 struct assoc_array_shortcut *shortcut;
     159                 :            :                 int             level;
     160                 :            :                 int             sc_level;
     161                 :            :                 unsigned long   sc_segments;
     162                 :            :                 unsigned long   dissimilarity;
     163                 :            :         } wrong_shortcut;
     164                 :            : };
     165                 :            : 
     166                 :            : /*
     167                 :            :  * Navigate through the internal tree looking for the closest node to the key.
     168                 :            :  */
     169                 :            : static enum assoc_array_walk_status
     170                 :      46809 : assoc_array_walk(const struct assoc_array *array,
     171                 :            :                  const struct assoc_array_ops *ops,
     172                 :            :                  const void *index_key,
     173                 :            :                  struct assoc_array_walk_result *result)
     174                 :            : {
     175                 :            :         struct assoc_array_shortcut *shortcut;
     176                 :            :         struct assoc_array_node *node;
     177                 :            :         struct assoc_array_ptr *cursor, *ptr;
     178                 :            :         unsigned long sc_segments, dissimilarity;
     179                 :            :         unsigned long segments;
     180                 :            :         int level, sc_level, next_sc_level;
     181                 :            :         int slot;
     182                 :            : 
     183                 :            :         pr_devel("-->%s()\n", __func__);
     184                 :            : 
     185                 :      46809 :         cursor = READ_ONCE(array->root);  /* Address dependency. */
     186         [ +  + ]:      46809 :         if (!cursor)
     187                 :            :                 return assoc_array_walk_tree_empty;
     188                 :            : 
     189                 :            :         level = 0;
     190                 :            : 
     191                 :            :         /* Use segments from the key for the new leaf to navigate through the
     192                 :            :          * internal tree, skipping through nodes and shortcuts that are on
     193                 :            :          * route to the destination.  Eventually we'll come to a slot that is
     194                 :            :          * either empty or contains a leaf at which point we've found a node in
     195                 :            :          * which the leaf we're looking for might be found or into which it
     196                 :            :          * should be inserted.
     197                 :            :          */
     198                 :            : jumped:
     199                 :      19253 :         segments = ops->get_key_chunk(index_key, level);
     200                 :            :         pr_devel("segments[%d]: %lx\n", level, segments);
     201                 :            : 
     202         [ +  - ]:      19258 :         if (assoc_array_ptr_is_shortcut(cursor))
     203                 :            :                 goto follow_shortcut;
     204                 :            : 
     205                 :            : consider_node:
     206                 :            :         node = assoc_array_ptr_to_node(cursor);
     207                 :      19258 :         slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
     208                 :      19258 :         slot &= ASSOC_ARRAY_FAN_MASK;
     209                 :      38516 :         ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */
     210                 :            : 
     211                 :            :         pr_devel("consider slot %x [ix=%d type=%lu]\n",
     212                 :            :                  slot, level, (unsigned long)ptr & 3);
     213                 :            : 
     214         [ +  - ]:      19258 :         if (!assoc_array_ptr_is_meta(ptr)) {
     215                 :            :                 /* The node doesn't have a node/shortcut pointer in the slot
     216                 :            :                  * corresponding to the index key that we have to follow.
     217                 :            :                  */
     218                 :      19258 :                 result->terminal_node.node = node;
     219                 :      19258 :                 result->terminal_node.level = level;
     220                 :      19258 :                 result->terminal_node.slot = slot;
     221                 :            :                 pr_devel("<--%s() = terminal_node\n", __func__);
     222                 :      19258 :                 return assoc_array_walk_found_terminal_node;
     223                 :            :         }
     224                 :            : 
     225         [ #  # ]:          0 :         if (assoc_array_ptr_is_node(ptr)) {
     226                 :            :                 /* There is a pointer to a node in the slot corresponding to
     227                 :            :                  * this index key segment, so we need to follow it.
     228                 :            :                  */
     229                 :            :                 cursor = ptr;
     230                 :          0 :                 level += ASSOC_ARRAY_LEVEL_STEP;
     231         [ #  # ]:          0 :                 if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0)
     232                 :            :                         goto consider_node;
     233                 :            :                 goto jumped;
     234                 :            :         }
     235                 :            : 
     236                 :            :         /* There is a shortcut in the slot corresponding to the index key
     237                 :            :          * segment.  We follow the shortcut if its partial index key matches
     238                 :            :          * this leaf's.  Otherwise we need to split the shortcut.
     239                 :            :          */
     240                 :          0 :         cursor = ptr;
     241                 :            : follow_shortcut:
     242                 :            :         shortcut = assoc_array_ptr_to_shortcut(cursor);
     243                 :            :         pr_devel("shortcut to %d\n", shortcut->skip_to_level);
     244                 :          0 :         sc_level = level + ASSOC_ARRAY_LEVEL_STEP;
     245         [ #  # ]:          0 :         BUG_ON(sc_level > shortcut->skip_to_level);
     246                 :            : 
     247                 :            :         do {
     248                 :            :                 /* Check the leaf against the shortcut's index key a word at a
     249                 :            :                  * time, trimming the final word (the shortcut stores the index
     250                 :            :                  * key completely from the root to the shortcut's target).
     251                 :            :                  */
     252         [ #  # ]:          0 :                 if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0)
     253                 :          0 :                         segments = ops->get_key_chunk(index_key, sc_level);
     254                 :            : 
     255                 :          0 :                 sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT];
     256                 :          0 :                 dissimilarity = segments ^ sc_segments;
     257                 :            : 
     258         [ #  # ]:          0 :                 if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) {
     259                 :            :                         /* Trim segments that are beyond the shortcut */
     260                 :          0 :                         int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK;
     261                 :          0 :                         dissimilarity &= ~(ULONG_MAX << shift);
     262                 :            :                         next_sc_level = shortcut->skip_to_level;
     263                 :            :                 } else {
     264                 :          0 :                         next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE;
     265                 :          0 :                         next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
     266                 :            :                 }
     267                 :            : 
     268         [ #  # ]:          0 :                 if (dissimilarity != 0) {
     269                 :            :                         /* This shortcut points elsewhere */
     270                 :          0 :                         result->wrong_shortcut.shortcut = shortcut;
     271                 :          0 :                         result->wrong_shortcut.level = level;
     272                 :          0 :                         result->wrong_shortcut.sc_level = sc_level;
     273                 :          0 :                         result->wrong_shortcut.sc_segments = sc_segments;
     274                 :          0 :                         result->wrong_shortcut.dissimilarity = dissimilarity;
     275                 :          0 :                         return assoc_array_walk_found_wrong_shortcut;
     276                 :            :                 }
     277                 :            : 
     278                 :            :                 sc_level = next_sc_level;
     279         [ #  # ]:          0 :         } while (sc_level < shortcut->skip_to_level);
     280                 :            : 
     281                 :            :         /* The shortcut matches the leaf's index to this point. */
     282                 :          0 :         cursor = READ_ONCE(shortcut->next_node); /* Address dependency. */
     283         [ #  # ]:          0 :         if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) {
     284                 :          0 :                 level = sc_level;
     285                 :          0 :                 goto jumped;
     286                 :            :         } else {
     287                 :          0 :                 level = sc_level;
     288                 :          0 :                 goto consider_node;
     289                 :            :         }
     290                 :            : }
     291                 :            : 
     292                 :            : /**
     293                 :            :  * assoc_array_find - Find an object by index key
     294                 :            :  * @array: The associative array to search.
     295                 :            :  * @ops: The operations to use.
     296                 :            :  * @index_key: The key to the object.
     297                 :            :  *
     298                 :            :  * Find an object in an associative array by walking through the internal tree
     299                 :            :  * to the node that should contain the object and then searching the leaves
     300                 :            :  * there.  NULL is returned if the requested object was not found in the array.
     301                 :            :  *
     302                 :            :  * The caller must hold the RCU read lock or better.
     303                 :            :  */
     304                 :      31274 : void *assoc_array_find(const struct assoc_array *array,
     305                 :            :                        const struct assoc_array_ops *ops,
     306                 :            :                        const void *index_key)
     307                 :            : {
     308                 :            :         struct assoc_array_walk_result result;
     309                 :            :         const struct assoc_array_node *node;
     310                 :            :         const struct assoc_array_ptr *ptr;
     311                 :            :         const void *leaf;
     312                 :            :         int slot;
     313                 :            : 
     314         [ +  + ]:      31274 :         if (assoc_array_walk(array, ops, index_key, &result) !=
     315                 :            :             assoc_array_walk_found_terminal_node)
     316                 :            :                 return NULL;
     317                 :            : 
     318                 :      17391 :         node = result.terminal_node.node;
     319                 :            : 
     320                 :            :         /* If the target key is available to us, it's has to be pointed to by
     321                 :            :          * the terminal node.
     322                 :            :          */
     323         [ +  + ]:      91037 :         for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
     324                 :     177510 :                 ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */
     325   [ +  +  +  + ]:     109666 :                 if (ptr && assoc_array_ptr_is_leaf(ptr)) {
     326                 :            :                         /* We need a barrier between the read of the pointer
     327                 :            :                          * and dereferencing the pointer - but only if we are
     328                 :            :                          * actually going to dereference it.
     329                 :            :                          */
     330                 :            :                         leaf = assoc_array_ptr_to_leaf(ptr);
     331         [ +  + ]:      20900 :                         if (ops->compare_object(leaf, index_key))
     332                 :      15119 :                                 return (void *)leaf;
     333                 :            :                 }
     334                 :            :         }
     335                 :            : 
     336                 :            :         return NULL;
     337                 :            : }
     338                 :            : 
     339                 :            : /*
     340                 :            :  * Destructively iterate over an associative array.  The caller must prevent
     341                 :            :  * other simultaneous accesses.
     342                 :            :  */
     343                 :       8498 : static void assoc_array_destroy_subtree(struct assoc_array_ptr *root,
     344                 :            :                                         const struct assoc_array_ops *ops)
     345                 :            : {
     346                 :            :         struct assoc_array_shortcut *shortcut;
     347                 :            :         struct assoc_array_node *node;
     348                 :            :         struct assoc_array_ptr *cursor, *parent = NULL;
     349                 :            :         int slot = -1;
     350                 :            : 
     351                 :            :         pr_devel("-->%s()\n", __func__);
     352                 :            : 
     353                 :            :         cursor = root;
     354         [ +  - ]:       8498 :         if (!cursor) {
     355                 :            :                 pr_devel("empty\n");
     356                 :            :                 return;
     357                 :            :         }
     358                 :            : 
     359                 :            : move_to_meta:
     360         [ -  + ]:       8498 :         if (assoc_array_ptr_is_shortcut(cursor)) {
     361                 :            :                 /* Descend through a shortcut */
     362                 :            :                 pr_devel("[%d] shortcut\n", slot);
     363         [ #  # ]:          0 :                 BUG_ON(!assoc_array_ptr_is_shortcut(cursor));
     364                 :            :                 shortcut = assoc_array_ptr_to_shortcut(cursor);
     365         [ #  # ]:          0 :                 BUG_ON(shortcut->back_pointer != parent);
     366   [ #  #  #  # ]:          0 :                 BUG_ON(slot != -1 && shortcut->parent_slot != slot);
     367                 :            :                 parent = cursor;
     368                 :          0 :                 cursor = shortcut->next_node;
     369                 :            :                 slot = -1;
     370         [ #  # ]:          0 :                 BUG_ON(!assoc_array_ptr_is_node(cursor));
     371                 :            :         }
     372                 :            : 
     373                 :            :         pr_devel("[%d] node\n", slot);
     374                 :            :         node = assoc_array_ptr_to_node(cursor);
     375         [ -  + ]:       8498 :         BUG_ON(node->back_pointer != parent);
     376   [ +  -  #  # ]:       8498 :         BUG_ON(slot != -1 && node->parent_slot != slot);
     377                 :            :         slot = 0;
     378                 :            : 
     379                 :            : continue_node:
     380                 :            :         pr_devel("Node %p [back=%p]\n", node, node->back_pointer);
     381         [ +  + ]:     144466 :         for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
     382                 :     135968 :                 struct assoc_array_ptr *ptr = node->slots[slot];
     383         [ +  + ]:     135968 :                 if (!ptr)
     384                 :     126229 :                         continue;
     385         [ -  + ]:       9739 :                 if (assoc_array_ptr_is_meta(ptr)) {
     386                 :          0 :                         parent = cursor;
     387                 :          0 :                         cursor = ptr;
     388                 :          0 :                         goto move_to_meta;
     389                 :            :                 }
     390                 :            : 
     391         [ +  - ]:       9739 :                 if (ops) {
     392                 :            :                         pr_devel("[%d] free leaf\n", slot);
     393                 :      19478 :                         ops->free_object(assoc_array_ptr_to_leaf(ptr));
     394                 :            :                 }
     395                 :            :         }
     396                 :            : 
     397                 :       8498 :         parent = node->back_pointer;
     398                 :       8498 :         slot = node->parent_slot;
     399                 :            :         pr_devel("free node\n");
     400                 :       8498 :         kfree(node);
     401         [ -  + ]:       8498 :         if (!parent)
     402                 :            :                 return; /* Done */
     403                 :            : 
     404                 :            :         /* Move back up to the parent (may need to free a shortcut on
     405                 :            :          * the way up) */
     406         [ #  # ]:          0 :         if (assoc_array_ptr_is_shortcut(parent)) {
     407                 :            :                 shortcut = assoc_array_ptr_to_shortcut(parent);
     408         [ #  # ]:          0 :                 BUG_ON(shortcut->next_node != cursor);
     409                 :            :                 cursor = parent;
     410                 :          0 :                 parent = shortcut->back_pointer;
     411                 :          0 :                 slot = shortcut->parent_slot;
     412                 :            :                 pr_devel("free shortcut\n");
     413                 :          0 :                 kfree(shortcut);
     414         [ #  # ]:          0 :                 if (!parent)
     415                 :            :                         return;
     416                 :            : 
     417         [ #  # ]:          0 :                 BUG_ON(!assoc_array_ptr_is_node(parent));
     418                 :            :         }
     419                 :            : 
     420                 :            :         /* Ascend to next slot in parent node */
     421                 :            :         pr_devel("ascend to %p[%d]\n", parent, slot);
     422                 :            :         cursor = parent;
     423                 :            :         node = assoc_array_ptr_to_node(cursor);
     424                 :          0 :         slot++;
     425                 :          0 :         goto continue_node;
     426                 :            : }
     427                 :            : 
     428                 :            : /**
     429                 :            :  * assoc_array_destroy - Destroy an associative array
     430                 :            :  * @array: The array to destroy.
     431                 :            :  * @ops: The operations to use.
     432                 :            :  *
     433                 :            :  * Discard all metadata and free all objects in an associative array.  The
     434                 :            :  * array will be empty and ready to use again upon completion.  This function
     435                 :            :  * cannot fail.
     436                 :            :  *
     437                 :            :  * The caller must prevent all other accesses whilst this takes place as no
     438                 :            :  * attempt is made to adjust pointers gracefully to permit RCU readlock-holding
     439                 :            :  * accesses to continue.  On the other hand, no memory allocation is required.
     440                 :            :  */
     441                 :       8498 : void assoc_array_destroy(struct assoc_array *array,
     442                 :            :                          const struct assoc_array_ops *ops)
     443                 :            : {
     444                 :       8498 :         assoc_array_destroy_subtree(array->root, ops);
     445                 :       8498 :         array->root = NULL;
     446                 :       8498 : }
     447                 :            : 
     448                 :            : /*
     449                 :            :  * Handle insertion into an empty tree.
     450                 :            :  */
     451                 :      13667 : static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit)
     452                 :            : {
     453                 :            :         struct assoc_array_node *new_n0;
     454                 :            : 
     455                 :            :         pr_devel("-->%s()\n", __func__);
     456                 :            : 
     457                 :      13667 :         new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
     458         [ +  + ]:      13671 :         if (!new_n0)
     459                 :            :                 return false;
     460                 :            : 
     461                 :      13670 :         edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
     462                 :      13670 :         edit->leaf_p = &new_n0->slots[0];
     463                 :      13670 :         edit->adjust_count_on = new_n0;
     464                 :      13670 :         edit->set[0].ptr = &edit->array->root;
     465                 :      13670 :         edit->set[0].to = assoc_array_node_to_ptr(new_n0);
     466                 :            : 
     467                 :            :         pr_devel("<--%s() = ok [no root]\n", __func__);
     468                 :      13670 :         return true;
     469                 :            : }
     470                 :            : 
     471                 :            : /*
     472                 :            :  * Handle insertion into a terminal node.
     473                 :            :  */
     474                 :       1862 : static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit,
     475                 :            :                                                   const struct assoc_array_ops *ops,
     476                 :            :                                                   const void *index_key,
     477                 :            :                                                   struct assoc_array_walk_result *result)
     478                 :            : {
     479                 :            :         struct assoc_array_shortcut *shortcut, *new_s0;
     480                 :            :         struct assoc_array_node *node, *new_n0, *new_n1, *side;
     481                 :            :         struct assoc_array_ptr *ptr;
     482                 :            :         unsigned long dissimilarity, base_seg, blank;
     483                 :            :         size_t keylen;
     484                 :            :         bool have_meta;
     485                 :            :         int level, diff;
     486                 :            :         int slot, next_slot, free_slot, i, j;
     487                 :            : 
     488                 :       1862 :         node    = result->terminal_node.node;
     489                 :       1862 :         level   = result->terminal_node.level;
     490                 :       1862 :         edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot;
     491                 :            : 
     492                 :            :         pr_devel("-->%s()\n", __func__);
     493                 :            : 
     494                 :            :         /* We arrived at a node which doesn't have an onward node or shortcut
     495                 :            :          * pointer that we have to follow.  This means that (a) the leaf we
     496                 :            :          * want must go here (either by insertion or replacement) or (b) we
     497                 :            :          * need to split this node and insert in one of the fragments.
     498                 :            :          */
     499                 :            :         free_slot = -1;
     500                 :            : 
     501                 :            :         /* Firstly, we have to check the leaves in this node to see if there's
     502                 :            :          * a matching one we should replace in place.
     503                 :            :          */
     504         [ +  + ]:      31654 :         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
     505                 :      29792 :                 ptr = node->slots[i];
     506         [ +  + ]:      29792 :                 if (!ptr) {
     507                 :            :                         free_slot = i;
     508                 :      27309 :                         continue;
     509                 :            :                 }
     510   [ +  -  -  + ]:       4966 :                 if (assoc_array_ptr_is_leaf(ptr) &&
     511                 :       4966 :                     ops->compare_object(assoc_array_ptr_to_leaf(ptr),
     512                 :            :                                         index_key)) {
     513                 :            :                         pr_devel("replace in slot %d\n", i);
     514                 :          0 :                         edit->leaf_p = &node->slots[i];
     515                 :          0 :                         edit->dead_leaf = node->slots[i];
     516                 :            :                         pr_devel("<--%s() = ok [replace]\n", __func__);
     517                 :          0 :                         return true;
     518                 :            :                 }
     519                 :            :         }
     520                 :            : 
     521                 :            :         /* If there is a free slot in this node then we can just insert the
     522                 :            :          * leaf here.
     523                 :            :          */
     524         [ +  - ]:       1862 :         if (free_slot >= 0) {
     525                 :            :                 pr_devel("insert in free slot %d\n", free_slot);
     526                 :       1862 :                 edit->leaf_p = &node->slots[free_slot];
     527                 :       1862 :                 edit->adjust_count_on = node;
     528                 :            :                 pr_devel("<--%s() = ok [insert]\n", __func__);
     529                 :       1862 :                 return true;
     530                 :            :         }
     531                 :            : 
     532                 :            :         /* The node has no spare slots - so we're either going to have to split
     533                 :            :          * it or insert another node before it.
     534                 :            :          *
     535                 :            :          * Whatever, we're going to need at least two new nodes - so allocate
     536                 :            :          * those now.  We may also need a new shortcut, but we deal with that
     537                 :            :          * when we need it.
     538                 :            :          */
     539                 :          0 :         new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
     540         [ #  # ]:          0 :         if (!new_n0)
     541                 :            :                 return false;
     542                 :          0 :         edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
     543                 :          0 :         new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
     544         [ #  # ]:          0 :         if (!new_n1)
     545                 :            :                 return false;
     546                 :          0 :         edit->new_meta[1] = assoc_array_node_to_ptr(new_n1);
     547                 :            : 
     548                 :            :         /* We need to find out how similar the leaves are. */
     549                 :            :         pr_devel("no spare slots\n");
     550                 :            :         have_meta = false;
     551         [ #  # ]:          0 :         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
     552                 :          0 :                 ptr = node->slots[i];
     553         [ #  # ]:          0 :                 if (assoc_array_ptr_is_meta(ptr)) {
     554                 :          0 :                         edit->segment_cache[i] = 0xff;
     555                 :            :                         have_meta = true;
     556                 :          0 :                         continue;
     557                 :            :                 }
     558                 :          0 :                 base_seg = ops->get_object_key_chunk(
     559                 :            :                         assoc_array_ptr_to_leaf(ptr), level);
     560                 :          0 :                 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
     561                 :          0 :                 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
     562                 :            :         }
     563                 :            : 
     564         [ #  # ]:          0 :         if (have_meta) {
     565                 :            :                 pr_devel("have meta\n");
     566                 :            :                 goto split_node;
     567                 :            :         }
     568                 :            : 
     569                 :            :         /* The node contains only leaves */
     570                 :            :         dissimilarity = 0;
     571                 :          0 :         base_seg = edit->segment_cache[0];
     572         [ #  # ]:          0 :         for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++)
     573                 :          0 :                 dissimilarity |= edit->segment_cache[i] ^ base_seg;
     574                 :            : 
     575                 :            :         pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity);
     576                 :            : 
     577         [ #  # ]:          0 :         if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) {
     578                 :            :                 /* The old leaves all cluster in the same slot.  We will need
     579                 :            :                  * to insert a shortcut if the new node wants to cluster with them.
     580                 :            :                  */
     581         [ #  # ]:          0 :                 if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0)
     582                 :            :                         goto all_leaves_cluster_together;
     583                 :            : 
     584                 :            :                 /* Otherwise all the old leaves cluster in the same slot, but
     585                 :            :                  * the new leaf wants to go into a different slot - so we
     586                 :            :                  * create a new node (n0) to hold the new leaf and a pointer to
     587                 :            :                  * a new node (n1) holding all the old leaves.
     588                 :            :                  *
     589                 :            :                  * This can be done by falling through to the node splitting
     590                 :            :                  * path.
     591                 :            :                  */
     592                 :            :                 pr_devel("present leaves cluster but not new leaf\n");
     593                 :            :         }
     594                 :            : 
     595                 :            : split_node:
     596                 :            :         pr_devel("split node\n");
     597                 :            : 
     598                 :            :         /* We need to split the current node.  The node must contain anything
     599                 :            :          * from a single leaf (in the one leaf case, this leaf will cluster
     600                 :            :          * with the new leaf) and the rest meta-pointers, to all leaves, some
     601                 :            :          * of which may cluster.
     602                 :            :          *
     603                 :            :          * It won't contain the case in which all the current leaves plus the
     604                 :            :          * new leaves want to cluster in the same slot.
     605                 :            :          *
     606                 :            :          * We need to expel at least two leaves out of a set consisting of the
     607                 :            :          * leaves in the node and the new leaf.  The current meta pointers can
     608                 :            :          * just be copied as they shouldn't cluster with any of the leaves.
     609                 :            :          *
     610                 :            :          * We need a new node (n0) to replace the current one and a new node to
     611                 :            :          * take the expelled nodes (n1).
     612                 :            :          */
     613                 :          0 :         edit->set[0].to = assoc_array_node_to_ptr(new_n0);
     614                 :          0 :         new_n0->back_pointer = node->back_pointer;
     615                 :          0 :         new_n0->parent_slot = node->parent_slot;
     616                 :          0 :         new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
     617                 :          0 :         new_n1->parent_slot = -1; /* Need to calculate this */
     618                 :            : 
     619                 :            : do_split_node:
     620                 :            :         pr_devel("do_split_node\n");
     621                 :            : 
     622                 :          0 :         new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
     623                 :          0 :         new_n1->nr_leaves_on_branch = 0;
     624                 :            : 
     625                 :            :         /* Begin by finding two matching leaves.  There have to be at least two
     626                 :            :          * that match - even if there are meta pointers - because any leaf that
     627                 :            :          * would match a slot with a meta pointer in it must be somewhere
     628                 :            :          * behind that meta pointer and cannot be here.  Further, given N
     629                 :            :          * remaining leaf slots, we now have N+1 leaves to go in them.
     630                 :            :          */
     631         [ #  # ]:          0 :         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
     632                 :          0 :                 slot = edit->segment_cache[i];
     633         [ #  # ]:          0 :                 if (slot != 0xff)
     634         [ #  # ]:          0 :                         for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++)
     635         [ #  # ]:          0 :                                 if (edit->segment_cache[j] == slot)
     636                 :            :                                         goto found_slot_for_multiple_occupancy;
     637                 :            :         }
     638                 :            : found_slot_for_multiple_occupancy:
     639                 :            :         pr_devel("same slot: %x %x [%02x]\n", i, j, slot);
     640         [ #  # ]:          0 :         BUG_ON(i >= ASSOC_ARRAY_FAN_OUT);
     641         [ #  # ]:          0 :         BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1);
     642         [ #  # ]:          0 :         BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT);
     643                 :            : 
     644                 :          0 :         new_n1->parent_slot = slot;
     645                 :            : 
     646                 :            :         /* Metadata pointers cannot change slot */
     647         [ #  # ]:          0 :         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++)
     648         [ #  # ]:          0 :                 if (assoc_array_ptr_is_meta(node->slots[i]))
     649                 :          0 :                         new_n0->slots[i] = node->slots[i];
     650                 :            :                 else
     651                 :          0 :                         new_n0->slots[i] = NULL;
     652         [ #  # ]:          0 :         BUG_ON(new_n0->slots[slot] != NULL);
     653                 :          0 :         new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1);
     654                 :            : 
     655                 :            :         /* Filter the leaf pointers between the new nodes */
     656                 :            :         free_slot = -1;
     657                 :            :         next_slot = 0;
     658         [ #  # ]:          0 :         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
     659         [ #  # ]:          0 :                 if (assoc_array_ptr_is_meta(node->slots[i]))
     660                 :          0 :                         continue;
     661         [ #  # ]:          0 :                 if (edit->segment_cache[i] == slot) {
     662                 :          0 :                         new_n1->slots[next_slot++] = node->slots[i];
     663                 :          0 :                         new_n1->nr_leaves_on_branch++;
     664                 :            :                 } else {
     665                 :            :                         do {
     666                 :          0 :                                 free_slot++;
     667         [ #  # ]:          0 :                         } while (new_n0->slots[free_slot] != NULL);
     668                 :          0 :                         new_n0->slots[free_slot] = node->slots[i];
     669                 :            :                 }
     670                 :            :         }
     671                 :            : 
     672                 :            :         pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot);
     673                 :            : 
     674         [ #  # ]:          0 :         if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) {
     675                 :            :                 do {
     676                 :          0 :                         free_slot++;
     677         [ #  # ]:          0 :                 } while (new_n0->slots[free_slot] != NULL);
     678                 :          0 :                 edit->leaf_p = &new_n0->slots[free_slot];
     679                 :          0 :                 edit->adjust_count_on = new_n0;
     680                 :            :         } else {
     681                 :          0 :                 edit->leaf_p = &new_n1->slots[next_slot++];
     682                 :          0 :                 edit->adjust_count_on = new_n1;
     683                 :            :         }
     684                 :            : 
     685         [ #  # ]:          0 :         BUG_ON(next_slot <= 1);
     686                 :            : 
     687                 :          0 :         edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0);
     688         [ #  # ]:          0 :         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
     689         [ #  # ]:          0 :                 if (edit->segment_cache[i] == 0xff) {
     690                 :          0 :                         ptr = node->slots[i];
     691         [ #  # ]:          0 :                         BUG_ON(assoc_array_ptr_is_leaf(ptr));
     692         [ #  # ]:          0 :                         if (assoc_array_ptr_is_node(ptr)) {
     693                 :            :                                 side = assoc_array_ptr_to_node(ptr);
     694                 :          0 :                                 edit->set_backpointers[i] = &side->back_pointer;
     695                 :            :                         } else {
     696                 :            :                                 shortcut = assoc_array_ptr_to_shortcut(ptr);
     697                 :          0 :                                 edit->set_backpointers[i] = &shortcut->back_pointer;
     698                 :            :                         }
     699                 :            :                 }
     700                 :            :         }
     701                 :            : 
     702                 :          0 :         ptr = node->back_pointer;
     703         [ #  # ]:          0 :         if (!ptr)
     704                 :          0 :                 edit->set[0].ptr = &edit->array->root;
     705         [ #  # ]:          0 :         else if (assoc_array_ptr_is_node(ptr))
     706                 :          0 :                 edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot];
     707                 :            :         else
     708                 :          0 :                 edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node;
     709                 :          0 :         edit->excised_meta[0] = assoc_array_node_to_ptr(node);
     710                 :            :         pr_devel("<--%s() = ok [split node]\n", __func__);
     711                 :          0 :         return true;
     712                 :            : 
     713                 :            : all_leaves_cluster_together:
     714                 :            :         /* All the leaves, new and old, want to cluster together in this node
     715                 :            :          * in the same slot, so we have to replace this node with a shortcut to
     716                 :            :          * skip over the identical parts of the key and then place a pair of
     717                 :            :          * nodes, one inside the other, at the end of the shortcut and
     718                 :            :          * distribute the keys between them.
     719                 :            :          *
     720                 :            :          * Firstly we need to work out where the leaves start diverging as a
     721                 :            :          * bit position into their keys so that we know how big the shortcut
     722                 :            :          * needs to be.
     723                 :            :          *
     724                 :            :          * We only need to make a single pass of N of the N+1 leaves because if
     725                 :            :          * any keys differ between themselves at bit X then at least one of
     726                 :            :          * them must also differ with the base key at bit X or before.
     727                 :            :          */
     728                 :            :         pr_devel("all leaves cluster together\n");
     729                 :            :         diff = INT_MAX;
     730         [ #  # ]:          0 :         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
     731                 :          0 :                 int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]),
     732                 :            :                                           index_key);
     733         [ #  # ]:          0 :                 if (x < diff) {
     734         [ #  # ]:          0 :                         BUG_ON(x < 0);
     735                 :            :                         diff = x;
     736                 :            :                 }
     737                 :            :         }
     738         [ #  # ]:          0 :         BUG_ON(diff == INT_MAX);
     739         [ #  # ]:          0 :         BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP);
     740                 :            : 
     741                 :          0 :         keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
     742                 :          0 :         keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
     743                 :            : 
     744                 :          0 :         new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
     745                 :            :                          keylen * sizeof(unsigned long), GFP_KERNEL);
     746         [ #  # ]:          0 :         if (!new_s0)
     747                 :            :                 return false;
     748                 :          0 :         edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0);
     749                 :            : 
     750                 :          0 :         edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
     751                 :          0 :         new_s0->back_pointer = node->back_pointer;
     752                 :          0 :         new_s0->parent_slot = node->parent_slot;
     753                 :          0 :         new_s0->next_node = assoc_array_node_to_ptr(new_n0);
     754                 :          0 :         new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
     755                 :          0 :         new_n0->parent_slot = 0;
     756                 :          0 :         new_n1->back_pointer = assoc_array_node_to_ptr(new_n0);
     757                 :          0 :         new_n1->parent_slot = -1; /* Need to calculate this */
     758                 :            : 
     759                 :          0 :         new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK;
     760                 :            :         pr_devel("skip_to_level = %d [diff %d]\n", level, diff);
     761         [ #  # ]:          0 :         BUG_ON(level <= 0);
     762                 :            : 
     763         [ #  # ]:          0 :         for (i = 0; i < keylen; i++)
     764                 :          0 :                 new_s0->index_key[i] =
     765                 :          0 :                         ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
     766                 :            : 
     767         [ #  # ]:          0 :         if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) {
     768                 :          0 :                 blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
     769                 :            :                 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
     770                 :          0 :                 new_s0->index_key[keylen - 1] &= ~blank;
     771                 :            :         }
     772                 :            : 
     773                 :            :         /* This now reduces to a node splitting exercise for which we'll need
     774                 :            :          * to regenerate the disparity table.
     775                 :            :          */
     776         [ #  # ]:          0 :         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
     777                 :          0 :                 ptr = node->slots[i];
     778                 :          0 :                 base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr),
     779                 :            :                                                      level);
     780                 :          0 :                 base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
     781                 :          0 :                 edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK;
     782                 :            :         }
     783                 :            : 
     784                 :          0 :         base_seg = ops->get_key_chunk(index_key, level);
     785                 :          0 :         base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK;
     786                 :          0 :         edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK;
     787                 :          0 :         goto do_split_node;
     788                 :            : }
     789                 :            : 
     790                 :            : /*
     791                 :            :  * Handle insertion into the middle of a shortcut.
     792                 :            :  */
     793                 :          0 : static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit,
     794                 :            :                                             const struct assoc_array_ops *ops,
     795                 :            :                                             struct assoc_array_walk_result *result)
     796                 :            : {
     797                 :            :         struct assoc_array_shortcut *shortcut, *new_s0, *new_s1;
     798                 :            :         struct assoc_array_node *node, *new_n0, *side;
     799                 :            :         unsigned long sc_segments, dissimilarity, blank;
     800                 :            :         size_t keylen;
     801                 :            :         int level, sc_level, diff;
     802                 :            :         int sc_slot;
     803                 :            : 
     804                 :          0 :         shortcut        = result->wrong_shortcut.shortcut;
     805                 :          0 :         level           = result->wrong_shortcut.level;
     806                 :          0 :         sc_level        = result->wrong_shortcut.sc_level;
     807                 :          0 :         sc_segments     = result->wrong_shortcut.sc_segments;
     808                 :          0 :         dissimilarity   = result->wrong_shortcut.dissimilarity;
     809                 :            : 
     810                 :            :         pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n",
     811                 :            :                  __func__, level, dissimilarity, sc_level);
     812                 :            : 
     813                 :            :         /* We need to split a shortcut and insert a node between the two
     814                 :            :          * pieces.  Zero-length pieces will be dispensed with entirely.
     815                 :            :          *
     816                 :            :          * First of all, we need to find out in which level the first
     817                 :            :          * difference was.
     818                 :            :          */
     819                 :            :         diff = __ffs(dissimilarity);
     820                 :          0 :         diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK;
     821                 :          0 :         diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK;
     822                 :            :         pr_devel("diff=%d\n", diff);
     823                 :            : 
     824         [ #  # ]:          0 :         if (!shortcut->back_pointer) {
     825                 :          0 :                 edit->set[0].ptr = &edit->array->root;
     826         [ #  # ]:          0 :         } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) {
     827                 :            :                 node = assoc_array_ptr_to_node(shortcut->back_pointer);
     828                 :          0 :                 edit->set[0].ptr = &node->slots[shortcut->parent_slot];
     829                 :            :         } else {
     830                 :          0 :                 BUG();
     831                 :            :         }
     832                 :            : 
     833                 :          0 :         edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut);
     834                 :            : 
     835                 :            :         /* Create a new node now since we're going to need it anyway */
     836                 :          0 :         new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
     837         [ #  # ]:          0 :         if (!new_n0)
     838                 :            :                 return false;
     839                 :          0 :         edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
     840                 :          0 :         edit->adjust_count_on = new_n0;
     841                 :            : 
     842                 :            :         /* Insert a new shortcut before the new node if this segment isn't of
     843                 :            :          * zero length - otherwise we just connect the new node directly to the
     844                 :            :          * parent.
     845                 :            :          */
     846                 :          0 :         level += ASSOC_ARRAY_LEVEL_STEP;
     847         [ #  # ]:          0 :         if (diff > level) {
     848                 :            :                 pr_devel("pre-shortcut %d...%d\n", level, diff);
     849                 :          0 :                 keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE);
     850                 :          0 :                 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
     851                 :            : 
     852                 :          0 :                 new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) +
     853                 :            :                                  keylen * sizeof(unsigned long), GFP_KERNEL);
     854         [ #  # ]:          0 :                 if (!new_s0)
     855                 :            :                         return false;
     856                 :          0 :                 edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0);
     857                 :          0 :                 edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0);
     858                 :          0 :                 new_s0->back_pointer = shortcut->back_pointer;
     859                 :          0 :                 new_s0->parent_slot = shortcut->parent_slot;
     860                 :          0 :                 new_s0->next_node = assoc_array_node_to_ptr(new_n0);
     861                 :          0 :                 new_s0->skip_to_level = diff;
     862                 :            : 
     863                 :          0 :                 new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0);
     864                 :          0 :                 new_n0->parent_slot = 0;
     865                 :            : 
     866                 :          0 :                 memcpy(new_s0->index_key, shortcut->index_key,
     867                 :            :                        keylen * sizeof(unsigned long));
     868                 :            : 
     869                 :          0 :                 blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
     870                 :            :                 pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank);
     871                 :          0 :                 new_s0->index_key[keylen - 1] &= ~blank;
     872                 :            :         } else {
     873                 :            :                 pr_devel("no pre-shortcut\n");
     874                 :          0 :                 edit->set[0].to = assoc_array_node_to_ptr(new_n0);
     875                 :          0 :                 new_n0->back_pointer = shortcut->back_pointer;
     876                 :          0 :                 new_n0->parent_slot = shortcut->parent_slot;
     877                 :            :         }
     878                 :            : 
     879                 :          0 :         side = assoc_array_ptr_to_node(shortcut->next_node);
     880                 :          0 :         new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch;
     881                 :            : 
     882                 :            :         /* We need to know which slot in the new node is going to take a
     883                 :            :          * metadata pointer.
     884                 :            :          */
     885                 :          0 :         sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK);
     886                 :          0 :         sc_slot &= ASSOC_ARRAY_FAN_MASK;
     887                 :            : 
     888                 :            :         pr_devel("new slot %lx >> %d -> %d\n",
     889                 :            :                  sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot);
     890                 :            : 
     891                 :            :         /* Determine whether we need to follow the new node with a replacement
     892                 :            :          * for the current shortcut.  We could in theory reuse the current
     893                 :            :          * shortcut if its parent slot number doesn't change - but that's a
     894                 :            :          * 1-in-16 chance so not worth expending the code upon.
     895                 :            :          */
     896                 :          0 :         level = diff + ASSOC_ARRAY_LEVEL_STEP;
     897         [ #  # ]:          0 :         if (level < shortcut->skip_to_level) {
     898                 :            :                 pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level);
     899                 :          0 :                 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
     900                 :          0 :                 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
     901                 :            : 
     902                 :          0 :                 new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) +
     903                 :            :                                  keylen * sizeof(unsigned long), GFP_KERNEL);
     904         [ #  # ]:          0 :                 if (!new_s1)
     905                 :            :                         return false;
     906                 :          0 :                 edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1);
     907                 :            : 
     908                 :          0 :                 new_s1->back_pointer = assoc_array_node_to_ptr(new_n0);
     909                 :          0 :                 new_s1->parent_slot = sc_slot;
     910                 :          0 :                 new_s1->next_node = shortcut->next_node;
     911                 :          0 :                 new_s1->skip_to_level = shortcut->skip_to_level;
     912                 :            : 
     913                 :          0 :                 new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1);
     914                 :            : 
     915                 :          0 :                 memcpy(new_s1->index_key, shortcut->index_key,
     916                 :            :                        keylen * sizeof(unsigned long));
     917                 :            : 
     918                 :          0 :                 edit->set[1].ptr = &side->back_pointer;
     919                 :          0 :                 edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1);
     920                 :            :         } else {
     921                 :            :                 pr_devel("no post-shortcut\n");
     922                 :            : 
     923                 :            :                 /* We don't have to replace the pointed-to node as long as we
     924                 :            :                  * use memory barriers to make sure the parent slot number is
     925                 :            :                  * changed before the back pointer (the parent slot number is
     926                 :            :                  * irrelevant to the old parent shortcut).
     927                 :            :                  */
     928                 :          0 :                 new_n0->slots[sc_slot] = shortcut->next_node;
     929                 :          0 :                 edit->set_parent_slot[0].p = &side->parent_slot;
     930                 :          0 :                 edit->set_parent_slot[0].to = sc_slot;
     931                 :          0 :                 edit->set[1].ptr = &side->back_pointer;
     932                 :          0 :                 edit->set[1].to = assoc_array_node_to_ptr(new_n0);
     933                 :            :         }
     934                 :            : 
     935                 :            :         /* Install the new leaf in a spare slot in the new node. */
     936         [ #  # ]:          0 :         if (sc_slot == 0)
     937                 :          0 :                 edit->leaf_p = &new_n0->slots[1];
     938                 :            :         else
     939                 :          0 :                 edit->leaf_p = &new_n0->slots[0];
     940                 :            : 
     941                 :            :         pr_devel("<--%s() = ok [split shortcut]\n", __func__);
     942                 :          0 :         return edit;
     943                 :            : }
     944                 :            : 
     945                 :            : /**
     946                 :            :  * assoc_array_insert - Script insertion of an object into an associative array
     947                 :            :  * @array: The array to insert into.
     948                 :            :  * @ops: The operations to use.
     949                 :            :  * @index_key: The key to insert at.
     950                 :            :  * @object: The object to insert.
     951                 :            :  *
     952                 :            :  * Precalculate and preallocate a script for the insertion or replacement of an
     953                 :            :  * object in an associative array.  This results in an edit script that can
     954                 :            :  * either be applied or cancelled.
     955                 :            :  *
     956                 :            :  * The function returns a pointer to an edit script or -ENOMEM.
     957                 :            :  *
     958                 :            :  * The caller should lock against other modifications and must continue to hold
     959                 :            :  * the lock until assoc_array_apply_edit() has been called.
     960                 :            :  *
     961                 :            :  * Accesses to the tree may take place concurrently with this function,
     962                 :            :  * provided they hold the RCU read lock.
     963                 :            :  */
     964                 :      15535 : struct assoc_array_edit *assoc_array_insert(struct assoc_array *array,
     965                 :            :                                             const struct assoc_array_ops *ops,
     966                 :            :                                             const void *index_key,
     967                 :            :                                             void *object)
     968                 :            : {
     969                 :            :         struct assoc_array_walk_result result;
     970                 :            :         struct assoc_array_edit *edit;
     971                 :            : 
     972                 :            :         pr_devel("-->%s()\n", __func__);
     973                 :            : 
     974                 :            :         /* The leaf pointer we're given must not have the bottom bit set as we
     975                 :            :          * use those for type-marking the pointer.  NULL pointers are also not
     976                 :            :          * allowed as they indicate an empty slot but we have to allow them
     977                 :            :          * here as they can be updated later.
     978                 :            :          */
     979         [ -  + ]:      15535 :         BUG_ON(assoc_array_ptr_is_meta(object));
     980                 :            : 
     981                 :      15535 :         edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
     982         [ +  - ]:      15531 :         if (!edit)
     983                 :            :                 return ERR_PTR(-ENOMEM);
     984                 :      15534 :         edit->array = array;
     985                 :      15534 :         edit->ops = ops;
     986                 :      15534 :         edit->leaf = assoc_array_leaf_to_ptr(object);
     987                 :      15534 :         edit->adjust_count_by = 1;
     988                 :            : 
     989   [ +  +  -  - ]:      15534 :         switch (assoc_array_walk(array, ops, index_key, &result)) {
     990                 :            :         case assoc_array_walk_tree_empty:
     991                 :            :                 /* Allocate a root node if there isn't one yet */
     992         [ +  + ]:      13667 :                 if (!assoc_array_insert_in_empty_tree(edit))
     993                 :            :                         goto enomem;
     994                 :            :                 return edit;
     995                 :            : 
     996                 :            :         case assoc_array_walk_found_terminal_node:
     997                 :            :                 /* We found a node that doesn't have a node/shortcut pointer in
     998                 :            :                  * the slot corresponding to the index key that we have to
     999                 :            :                  * follow.
    1000                 :            :                  */
    1001         [ -  + ]:       1862 :                 if (!assoc_array_insert_into_terminal_node(edit, ops, index_key,
    1002                 :            :                                                            &result))
    1003                 :            :                         goto enomem;
    1004                 :            :                 return edit;
    1005                 :            : 
    1006                 :            :         case assoc_array_walk_found_wrong_shortcut:
    1007                 :            :                 /* We found a shortcut that didn't match our key in a slot we
    1008                 :            :                  * needed to follow.
    1009                 :            :                  */
    1010         [ #  # ]:          0 :                 if (!assoc_array_insert_mid_shortcut(edit, ops, &result))
    1011                 :            :                         goto enomem;
    1012                 :            :                 return edit;
    1013                 :            :         }
    1014                 :            : 
    1015                 :            : enomem:
    1016                 :            :         /* Clean up after an out of memory error */
    1017                 :            :         pr_devel("enomem\n");
    1018                 :          2 :         assoc_array_cancel_edit(edit);
    1019                 :          0 :         return ERR_PTR(-ENOMEM);
    1020                 :            : }
    1021                 :            : 
    1022                 :            : /**
    1023                 :            :  * assoc_array_insert_set_object - Set the new object pointer in an edit script
    1024                 :            :  * @edit: The edit script to modify.
    1025                 :            :  * @object: The object pointer to set.
    1026                 :            :  *
    1027                 :            :  * Change the object to be inserted in an edit script.  The object pointed to
    1028                 :            :  * by the old object is not freed.  This must be done prior to applying the
    1029                 :            :  * script.
    1030                 :            :  */
    1031                 :      15535 : void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object)
    1032                 :            : {
    1033         [ -  + ]:      15535 :         BUG_ON(!object);
    1034                 :      15535 :         edit->leaf = assoc_array_leaf_to_ptr(object);
    1035                 :      15535 : }
    1036                 :            : 
    1037                 :            : struct assoc_array_delete_collapse_context {
    1038                 :            :         struct assoc_array_node *node;
    1039                 :            :         const void              *skip_leaf;
    1040                 :            :         int                     slot;
    1041                 :            : };
    1042                 :            : 
    1043                 :            : /*
    1044                 :            :  * Subtree collapse to node iterator.
    1045                 :            :  */
    1046                 :          0 : static int assoc_array_delete_collapse_iterator(const void *leaf,
    1047                 :            :                                                 void *iterator_data)
    1048                 :            : {
    1049                 :            :         struct assoc_array_delete_collapse_context *collapse = iterator_data;
    1050                 :            : 
    1051         [ #  # ]:          0 :         if (leaf == collapse->skip_leaf)
    1052                 :            :                 return 0;
    1053                 :            : 
    1054         [ #  # ]:          0 :         BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT);
    1055                 :            : 
    1056                 :          0 :         collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf);
    1057                 :          0 :         return 0;
    1058                 :            : }
    1059                 :            : 
    1060                 :            : /**
    1061                 :            :  * assoc_array_delete - Script deletion of an object from an associative array
    1062                 :            :  * @array: The array to search.
    1063                 :            :  * @ops: The operations to use.
    1064                 :            :  * @index_key: The key to the object.
    1065                 :            :  *
    1066                 :            :  * Precalculate and preallocate a script for the deletion of an object from an
    1067                 :            :  * associative array.  This results in an edit script that can either be
    1068                 :            :  * applied or cancelled.
    1069                 :            :  *
    1070                 :            :  * The function returns a pointer to an edit script if the object was found,
    1071                 :            :  * NULL if the object was not found or -ENOMEM.
    1072                 :            :  *
    1073                 :            :  * The caller should lock against other modifications and must continue to hold
    1074                 :            :  * the lock until assoc_array_apply_edit() has been called.
    1075                 :            :  *
    1076                 :            :  * Accesses to the tree may take place concurrently with this function,
    1077                 :            :  * provided they hold the RCU read lock.
    1078                 :            :  */
    1079                 :          0 : struct assoc_array_edit *assoc_array_delete(struct assoc_array *array,
    1080                 :            :                                             const struct assoc_array_ops *ops,
    1081                 :            :                                             const void *index_key)
    1082                 :            : {
    1083                 :            :         struct assoc_array_delete_collapse_context collapse;
    1084                 :            :         struct assoc_array_walk_result result;
    1085                 :            :         struct assoc_array_node *node, *new_n0;
    1086                 :            :         struct assoc_array_edit *edit;
    1087                 :            :         struct assoc_array_ptr *ptr;
    1088                 :            :         bool has_meta;
    1089                 :            :         int slot, i;
    1090                 :            : 
    1091                 :            :         pr_devel("-->%s()\n", __func__);
    1092                 :            : 
    1093                 :          0 :         edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
    1094         [ #  # ]:          0 :         if (!edit)
    1095                 :            :                 return ERR_PTR(-ENOMEM);
    1096                 :          0 :         edit->array = array;
    1097                 :          0 :         edit->ops = ops;
    1098                 :          0 :         edit->adjust_count_by = -1;
    1099                 :            : 
    1100         [ #  # ]:          0 :         switch (assoc_array_walk(array, ops, index_key, &result)) {
    1101                 :            :         case assoc_array_walk_found_terminal_node:
    1102                 :            :                 /* We found a node that should contain the leaf we've been
    1103                 :            :                  * asked to remove - *if* it's in the tree.
    1104                 :            :                  */
    1105                 :            :                 pr_devel("terminal_node\n");
    1106                 :          0 :                 node = result.terminal_node.node;
    1107                 :            : 
    1108         [ #  # ]:          0 :                 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
    1109                 :          0 :                         ptr = node->slots[slot];
    1110   [ #  #  #  # ]:          0 :                         if (ptr &&
    1111         [ #  # ]:          0 :                             assoc_array_ptr_is_leaf(ptr) &&
    1112                 :          0 :                             ops->compare_object(assoc_array_ptr_to_leaf(ptr),
    1113                 :            :                                                 index_key))
    1114                 :            :                                 goto found_leaf;
    1115                 :            :                 }
    1116                 :            :                 /* fall through */
    1117                 :            :         case assoc_array_walk_tree_empty:
    1118                 :            :         case assoc_array_walk_found_wrong_shortcut:
    1119                 :            :         default:
    1120                 :          0 :                 assoc_array_cancel_edit(edit);
    1121                 :            :                 pr_devel("not found\n");
    1122                 :          0 :                 return NULL;
    1123                 :            :         }
    1124                 :            : 
    1125                 :            : found_leaf:
    1126         [ #  # ]:          0 :         BUG_ON(array->nr_leaves_on_tree <= 0);
    1127                 :            : 
    1128                 :            :         /* In the simplest form of deletion we just clear the slot and release
    1129                 :            :          * the leaf after a suitable interval.
    1130                 :            :          */
    1131                 :          0 :         edit->dead_leaf = node->slots[slot];
    1132                 :          0 :         edit->set[0].ptr = &node->slots[slot];
    1133                 :          0 :         edit->set[0].to = NULL;
    1134                 :          0 :         edit->adjust_count_on = node;
    1135                 :            : 
    1136                 :            :         /* If that concludes erasure of the last leaf, then delete the entire
    1137                 :            :          * internal array.
    1138                 :            :          */
    1139         [ #  # ]:          0 :         if (array->nr_leaves_on_tree == 1) {
    1140                 :          0 :                 edit->set[1].ptr = &array->root;
    1141                 :          0 :                 edit->set[1].to = NULL;
    1142                 :          0 :                 edit->adjust_count_on = NULL;
    1143                 :          0 :                 edit->excised_subtree = array->root;
    1144                 :            :                 pr_devel("all gone\n");
    1145                 :          0 :                 return edit;
    1146                 :            :         }
    1147                 :            : 
    1148                 :            :         /* However, we'd also like to clear up some metadata blocks if we
    1149                 :            :          * possibly can.
    1150                 :            :          *
    1151                 :            :          * We go for a simple algorithm of: if this node has FAN_OUT or fewer
    1152                 :            :          * leaves in it, then attempt to collapse it - and attempt to
    1153                 :            :          * recursively collapse up the tree.
    1154                 :            :          *
    1155                 :            :          * We could also try and collapse in partially filled subtrees to take
    1156                 :            :          * up space in this node.
    1157                 :            :          */
    1158         [ #  # ]:          0 :         if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
    1159                 :            :                 struct assoc_array_node *parent, *grandparent;
    1160                 :            :                 struct assoc_array_ptr *ptr;
    1161                 :            : 
    1162                 :            :                 /* First of all, we need to know if this node has metadata so
    1163                 :            :                  * that we don't try collapsing if all the leaves are already
    1164                 :            :                  * here.
    1165                 :            :                  */
    1166                 :            :                 has_meta = false;
    1167         [ #  # ]:          0 :                 for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
    1168                 :          0 :                         ptr = node->slots[i];
    1169         [ #  # ]:          0 :                         if (assoc_array_ptr_is_meta(ptr)) {
    1170                 :            :                                 has_meta = true;
    1171                 :            :                                 break;
    1172                 :            :                         }
    1173                 :            :                 }
    1174                 :            : 
    1175                 :            :                 pr_devel("leaves: %ld [m=%d]\n",
    1176                 :            :                          node->nr_leaves_on_branch - 1, has_meta);
    1177                 :            : 
    1178                 :            :                 /* Look further up the tree to see if we can collapse this node
    1179                 :            :                  * into a more proximal node too.
    1180                 :            :                  */
    1181                 :            :                 parent = node;
    1182                 :            :         collapse_up:
    1183                 :            :                 pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch);
    1184                 :            : 
    1185                 :          0 :                 ptr = parent->back_pointer;
    1186         [ #  # ]:          0 :                 if (!ptr)
    1187                 :            :                         goto do_collapse;
    1188         [ #  # ]:          0 :                 if (assoc_array_ptr_is_shortcut(ptr)) {
    1189                 :            :                         struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr);
    1190                 :          0 :                         ptr = s->back_pointer;
    1191         [ #  # ]:          0 :                         if (!ptr)
    1192                 :            :                                 goto do_collapse;
    1193                 :            :                 }
    1194                 :            : 
    1195                 :            :                 grandparent = assoc_array_ptr_to_node(ptr);
    1196         [ #  # ]:          0 :                 if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) {
    1197                 :            :                         parent = grandparent;
    1198                 :            :                         goto collapse_up;
    1199                 :            :                 }
    1200                 :            : 
    1201                 :            :         do_collapse:
    1202                 :            :                 /* There's no point collapsing if the original node has no meta
    1203                 :            :                  * pointers to discard and if we didn't merge into one of that
    1204                 :            :                  * node's ancestry.
    1205                 :            :                  */
    1206         [ #  # ]:          0 :                 if (has_meta || parent != node) {
    1207                 :          0 :                         node = parent;
    1208                 :            : 
    1209                 :            :                         /* Create a new node to collapse into */
    1210                 :          0 :                         new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
    1211         [ #  # ]:          0 :                         if (!new_n0)
    1212                 :            :                                 goto enomem;
    1213                 :          0 :                         edit->new_meta[0] = assoc_array_node_to_ptr(new_n0);
    1214                 :            : 
    1215                 :          0 :                         new_n0->back_pointer = node->back_pointer;
    1216                 :          0 :                         new_n0->parent_slot = node->parent_slot;
    1217                 :          0 :                         new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch;
    1218                 :          0 :                         edit->adjust_count_on = new_n0;
    1219                 :            : 
    1220                 :          0 :                         collapse.node = new_n0;
    1221                 :          0 :                         collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf);
    1222                 :          0 :                         collapse.slot = 0;
    1223                 :          0 :                         assoc_array_subtree_iterate(assoc_array_node_to_ptr(node),
    1224                 :          0 :                                                     node->back_pointer,
    1225                 :            :                                                     assoc_array_delete_collapse_iterator,
    1226                 :            :                                                     &collapse);
    1227                 :            :                         pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch);
    1228         [ #  # ]:          0 :                         BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1);
    1229                 :            : 
    1230         [ #  # ]:          0 :                         if (!node->back_pointer) {
    1231                 :          0 :                                 edit->set[1].ptr = &array->root;
    1232         [ #  # ]:          0 :                         } else if (assoc_array_ptr_is_leaf(node->back_pointer)) {
    1233                 :          0 :                                 BUG();
    1234         [ #  # ]:          0 :                         } else if (assoc_array_ptr_is_node(node->back_pointer)) {
    1235                 :            :                                 struct assoc_array_node *p =
    1236                 :            :                                         assoc_array_ptr_to_node(node->back_pointer);
    1237                 :          0 :                                 edit->set[1].ptr = &p->slots[node->parent_slot];
    1238         [ #  # ]:          0 :                         } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) {
    1239                 :            :                                 struct assoc_array_shortcut *s =
    1240                 :            :                                         assoc_array_ptr_to_shortcut(node->back_pointer);
    1241                 :          0 :                                 edit->set[1].ptr = &s->next_node;
    1242                 :            :                         }
    1243                 :          0 :                         edit->set[1].to = assoc_array_node_to_ptr(new_n0);
    1244                 :          0 :                         edit->excised_subtree = assoc_array_node_to_ptr(node);
    1245                 :            :                 }
    1246                 :            :         }
    1247                 :            : 
    1248                 :          0 :         return edit;
    1249                 :            : 
    1250                 :            : enomem:
    1251                 :            :         /* Clean up after an out of memory error */
    1252                 :            :         pr_devel("enomem\n");
    1253                 :          0 :         assoc_array_cancel_edit(edit);
    1254                 :          0 :         return ERR_PTR(-ENOMEM);
    1255                 :            : }
    1256                 :            : 
    1257                 :            : /**
    1258                 :            :  * assoc_array_clear - Script deletion of all objects from an associative array
    1259                 :            :  * @array: The array to clear.
    1260                 :            :  * @ops: The operations to use.
    1261                 :            :  *
    1262                 :            :  * Precalculate and preallocate a script for the deletion of all the objects
    1263                 :            :  * from an associative array.  This results in an edit script that can either
    1264                 :            :  * be applied or cancelled.
    1265                 :            :  *
    1266                 :            :  * The function returns a pointer to an edit script if there are objects to be
    1267                 :            :  * deleted, NULL if there are no objects in the array or -ENOMEM.
    1268                 :            :  *
    1269                 :            :  * The caller should lock against other modifications and must continue to hold
    1270                 :            :  * the lock until assoc_array_apply_edit() has been called.
    1271                 :            :  *
    1272                 :            :  * Accesses to the tree may take place concurrently with this function,
    1273                 :            :  * provided they hold the RCU read lock.
    1274                 :            :  */
    1275                 :          0 : struct assoc_array_edit *assoc_array_clear(struct assoc_array *array,
    1276                 :            :                                            const struct assoc_array_ops *ops)
    1277                 :            : {
    1278                 :            :         struct assoc_array_edit *edit;
    1279                 :            : 
    1280                 :            :         pr_devel("-->%s()\n", __func__);
    1281                 :            : 
    1282         [ #  # ]:          0 :         if (!array->root)
    1283                 :            :                 return NULL;
    1284                 :            : 
    1285                 :          0 :         edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
    1286         [ #  # ]:          0 :         if (!edit)
    1287                 :            :                 return ERR_PTR(-ENOMEM);
    1288                 :          0 :         edit->array = array;
    1289                 :          0 :         edit->ops = ops;
    1290                 :          0 :         edit->set[1].ptr = &array->root;
    1291                 :          0 :         edit->set[1].to = NULL;
    1292                 :          0 :         edit->excised_subtree = array->root;
    1293                 :          0 :         edit->ops_for_excised_subtree = ops;
    1294                 :            :         pr_devel("all gone\n");
    1295                 :          0 :         return edit;
    1296                 :            : }
    1297                 :            : 
    1298                 :            : /*
    1299                 :            :  * Handle the deferred destruction after an applied edit.
    1300                 :            :  */
    1301                 :      15535 : static void assoc_array_rcu_cleanup(struct rcu_head *head)
    1302                 :            : {
    1303                 :            :         struct assoc_array_edit *edit =
    1304                 :            :                 container_of(head, struct assoc_array_edit, rcu);
    1305                 :            :         int i;
    1306                 :            : 
    1307                 :            :         pr_devel("-->%s()\n", __func__);
    1308                 :            : 
    1309         [ -  + ]:      15535 :         if (edit->dead_leaf)
    1310                 :          0 :                 edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf));
    1311         [ +  + ]:      15532 :         for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++)
    1312         [ -  + ]:      15535 :                 if (edit->excised_meta[i])
    1313                 :          0 :                         kfree(assoc_array_ptr_to_node(edit->excised_meta[i]));
    1314                 :            : 
    1315         [ -  + ]:      15532 :         if (edit->excised_subtree) {
    1316         [ #  # ]:          0 :                 BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree));
    1317         [ #  # ]:          0 :                 if (assoc_array_ptr_is_node(edit->excised_subtree)) {
    1318                 :            :                         struct assoc_array_node *n =
    1319                 :            :                                 assoc_array_ptr_to_node(edit->excised_subtree);
    1320                 :          0 :                         n->back_pointer = NULL;
    1321                 :            :                 } else {
    1322                 :            :                         struct assoc_array_shortcut *s =
    1323                 :            :                                 assoc_array_ptr_to_shortcut(edit->excised_subtree);
    1324                 :          0 :                         s->back_pointer = NULL;
    1325                 :            :                 }
    1326                 :          0 :                 assoc_array_destroy_subtree(edit->excised_subtree,
    1327                 :            :                                             edit->ops_for_excised_subtree);
    1328                 :            :         }
    1329                 :            : 
    1330                 :      15532 :         kfree(edit);
    1331                 :      15535 : }
    1332                 :            : 
    1333                 :            : /**
    1334                 :            :  * assoc_array_apply_edit - Apply an edit script to an associative array
    1335                 :            :  * @edit: The script to apply.
    1336                 :            :  *
    1337                 :            :  * Apply an edit script to an associative array to effect an insertion,
    1338                 :            :  * deletion or clearance.  As the edit script includes preallocated memory,
    1339                 :            :  * this is guaranteed not to fail.
    1340                 :            :  *
    1341                 :            :  * The edit script, dead objects and dead metadata will be scheduled for
    1342                 :            :  * destruction after an RCU grace period to permit those doing read-only
    1343                 :            :  * accesses on the array to continue to do so under the RCU read lock whilst
    1344                 :            :  * the edit is taking place.
    1345                 :            :  */
    1346                 :      15535 : void assoc_array_apply_edit(struct assoc_array_edit *edit)
    1347                 :            : {
    1348                 :            :         struct assoc_array_shortcut *shortcut;
    1349                 :            :         struct assoc_array_node *node;
    1350                 :            :         struct assoc_array_ptr *ptr;
    1351                 :            :         int i;
    1352                 :            : 
    1353                 :            :         pr_devel("-->%s()\n", __func__);
    1354                 :            : 
    1355                 :      15535 :         smp_wmb();
    1356         [ +  - ]:      15535 :         if (edit->leaf_p)
    1357                 :      15535 :                 *edit->leaf_p = edit->leaf;
    1358                 :            : 
    1359                 :      15535 :         smp_wmb();
    1360         [ +  + ]:      31070 :         for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++)
    1361         [ -  + ]:      15535 :                 if (edit->set_parent_slot[i].p)
    1362                 :          0 :                         *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to;
    1363                 :            : 
    1364                 :      15535 :         smp_wmb();
    1365         [ +  + ]:     264095 :         for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++)
    1366         [ -  + ]:     248560 :                 if (edit->set_backpointers[i])
    1367                 :          0 :                         *edit->set_backpointers[i] = edit->set_backpointers_to;
    1368                 :            : 
    1369                 :      15535 :         smp_wmb();
    1370         [ +  + ]:      46605 :         for (i = 0; i < ARRAY_SIZE(edit->set); i++)
    1371         [ +  + ]:      31070 :                 if (edit->set[i].ptr)
    1372                 :      13673 :                         *edit->set[i].ptr = edit->set[i].to;
    1373                 :            : 
    1374         [ -  + ]:      15535 :         if (edit->array->root == NULL) {
    1375                 :          0 :                 edit->array->nr_leaves_on_tree = 0;
    1376         [ +  - ]:      15535 :         } else if (edit->adjust_count_on) {
    1377                 :            :                 node = edit->adjust_count_on;
    1378                 :            :                 for (;;) {
    1379                 :      15535 :                         node->nr_leaves_on_branch += edit->adjust_count_by;
    1380                 :            : 
    1381                 :      15535 :                         ptr = node->back_pointer;
    1382         [ -  + ]:      15535 :                         if (!ptr)
    1383                 :            :                                 break;
    1384         [ #  # ]:          0 :                         if (assoc_array_ptr_is_shortcut(ptr)) {
    1385                 :            :                                 shortcut = assoc_array_ptr_to_shortcut(ptr);
    1386                 :          0 :                                 ptr = shortcut->back_pointer;
    1387         [ #  # ]:          0 :                                 if (!ptr)
    1388                 :            :                                         break;
    1389                 :            :                         }
    1390         [ #  # ]:          0 :                         BUG_ON(!assoc_array_ptr_is_node(ptr));
    1391                 :            :                         node = assoc_array_ptr_to_node(ptr);
    1392                 :            :                 }
    1393                 :            : 
    1394                 :      15535 :                 edit->array->nr_leaves_on_tree += edit->adjust_count_by;
    1395                 :            :         }
    1396                 :            : 
    1397                 :      15535 :         call_rcu(&edit->rcu, assoc_array_rcu_cleanup);
    1398                 :      15535 : }
    1399                 :            : 
    1400                 :            : /**
    1401                 :            :  * assoc_array_cancel_edit - Discard an edit script.
    1402                 :            :  * @edit: The script to discard.
    1403                 :            :  *
    1404                 :            :  * Free an edit script and all the preallocated data it holds without making
    1405                 :            :  * any changes to the associative array it was intended for.
    1406                 :            :  *
    1407                 :            :  * NOTE!  In the case of an insertion script, this does _not_ release the leaf
    1408                 :            :  * that was to be inserted.  That is left to the caller.
    1409                 :            :  */
    1410                 :          0 : void assoc_array_cancel_edit(struct assoc_array_edit *edit)
    1411                 :            : {
    1412                 :            :         struct assoc_array_ptr *ptr;
    1413                 :            :         int i;
    1414                 :            : 
    1415                 :            :         pr_devel("-->%s()\n", __func__);
    1416                 :            : 
    1417                 :            :         /* Clean up after an out of memory error */
    1418         [ #  # ]:          0 :         for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) {
    1419                 :          0 :                 ptr = edit->new_meta[i];
    1420         [ #  # ]:          0 :                 if (ptr) {
    1421         [ #  # ]:          0 :                         if (assoc_array_ptr_is_node(ptr))
    1422                 :          0 :                                 kfree(assoc_array_ptr_to_node(ptr));
    1423                 :            :                         else
    1424                 :          0 :                                 kfree(assoc_array_ptr_to_shortcut(ptr));
    1425                 :            :                 }
    1426                 :            :         }
    1427                 :          0 :         kfree(edit);
    1428                 :          0 : }
    1429                 :            : 
    1430                 :            : /**
    1431                 :            :  * assoc_array_gc - Garbage collect an associative array.
    1432                 :            :  * @array: The array to clean.
    1433                 :            :  * @ops: The operations to use.
    1434                 :            :  * @iterator: A callback function to pass judgement on each object.
    1435                 :            :  * @iterator_data: Private data for the callback function.
    1436                 :            :  *
    1437                 :            :  * Collect garbage from an associative array and pack down the internal tree to
    1438                 :            :  * save memory.
    1439                 :            :  *
    1440                 :            :  * The iterator function is asked to pass judgement upon each object in the
    1441                 :            :  * array.  If it returns false, the object is discard and if it returns true,
    1442                 :            :  * the object is kept.  If it returns true, it must increment the object's
    1443                 :            :  * usage count (or whatever it needs to do to retain it) before returning.
    1444                 :            :  *
    1445                 :            :  * This function returns 0 if successful or -ENOMEM if out of memory.  In the
    1446                 :            :  * latter case, the array is not changed.
    1447                 :            :  *
    1448                 :            :  * The caller should lock against other modifications and must continue to hold
    1449                 :            :  * the lock until assoc_array_apply_edit() has been called.
    1450                 :            :  *
    1451                 :            :  * Accesses to the tree may take place concurrently with this function,
    1452                 :            :  * provided they hold the RCU read lock.
    1453                 :            :  */
    1454                 :          0 : int assoc_array_gc(struct assoc_array *array,
    1455                 :            :                    const struct assoc_array_ops *ops,
    1456                 :            :                    bool (*iterator)(void *object, void *iterator_data),
    1457                 :            :                    void *iterator_data)
    1458                 :            : {
    1459                 :            :         struct assoc_array_shortcut *shortcut, *new_s;
    1460                 :            :         struct assoc_array_node *node, *new_n;
    1461                 :            :         struct assoc_array_edit *edit;
    1462                 :            :         struct assoc_array_ptr *cursor, *ptr;
    1463                 :            :         struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp;
    1464                 :            :         unsigned long nr_leaves_on_tree;
    1465                 :            :         int keylen, slot, nr_free, next_slot, i;
    1466                 :            : 
    1467                 :            :         pr_devel("-->%s()\n", __func__);
    1468                 :            : 
    1469         [ #  # ]:          0 :         if (!array->root)
    1470                 :            :                 return 0;
    1471                 :            : 
    1472                 :          0 :         edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL);
    1473         [ #  # ]:          0 :         if (!edit)
    1474                 :            :                 return -ENOMEM;
    1475                 :          0 :         edit->array = array;
    1476                 :          0 :         edit->ops = ops;
    1477                 :          0 :         edit->ops_for_excised_subtree = ops;
    1478                 :          0 :         edit->set[0].ptr = &array->root;
    1479                 :          0 :         edit->excised_subtree = array->root;
    1480                 :            : 
    1481                 :          0 :         new_root = new_parent = NULL;
    1482                 :            :         new_ptr_pp = &new_root;
    1483                 :          0 :         cursor = array->root;
    1484                 :            : 
    1485                 :            : descend:
    1486                 :            :         /* If this point is a shortcut, then we need to duplicate it and
    1487                 :            :          * advance the target cursor.
    1488                 :            :          */
    1489         [ #  # ]:          0 :         if (assoc_array_ptr_is_shortcut(cursor)) {
    1490                 :            :                 shortcut = assoc_array_ptr_to_shortcut(cursor);
    1491                 :          0 :                 keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE);
    1492                 :          0 :                 keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT;
    1493                 :          0 :                 new_s = kmalloc(sizeof(struct assoc_array_shortcut) +
    1494                 :            :                                 keylen * sizeof(unsigned long), GFP_KERNEL);
    1495         [ #  # ]:          0 :                 if (!new_s)
    1496                 :            :                         goto enomem;
    1497                 :            :                 pr_devel("dup shortcut %p -> %p\n", shortcut, new_s);
    1498                 :          0 :                 memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) +
    1499                 :            :                                          keylen * sizeof(unsigned long)));
    1500                 :          0 :                 new_s->back_pointer = new_parent;
    1501                 :          0 :                 new_s->parent_slot = shortcut->parent_slot;
    1502                 :          0 :                 *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s);
    1503                 :          0 :                 new_ptr_pp = &new_s->next_node;
    1504                 :          0 :                 cursor = shortcut->next_node;
    1505                 :            :         }
    1506                 :            : 
    1507                 :            :         /* Duplicate the node at this position */
    1508                 :            :         node = assoc_array_ptr_to_node(cursor);
    1509                 :          0 :         new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL);
    1510         [ #  # ]:          0 :         if (!new_n)
    1511                 :            :                 goto enomem;
    1512                 :            :         pr_devel("dup node %p -> %p\n", node, new_n);
    1513                 :          0 :         new_n->back_pointer = new_parent;
    1514                 :          0 :         new_n->parent_slot = node->parent_slot;
    1515                 :          0 :         *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n);
    1516                 :            :         new_ptr_pp = NULL;
    1517                 :            :         slot = 0;
    1518                 :            : 
    1519                 :            : continue_node:
    1520                 :            :         /* Filter across any leaves and gc any subtrees */
    1521         [ #  # ]:          0 :         for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
    1522                 :          0 :                 ptr = node->slots[slot];
    1523         [ #  # ]:          0 :                 if (!ptr)
    1524                 :          0 :                         continue;
    1525                 :            : 
    1526         [ #  # ]:          0 :                 if (assoc_array_ptr_is_leaf(ptr)) {
    1527         [ #  # ]:          0 :                         if (iterator(assoc_array_ptr_to_leaf(ptr),
    1528                 :            :                                      iterator_data))
    1529                 :            :                                 /* The iterator will have done any reference
    1530                 :            :                                  * counting on the object for us.
    1531                 :            :                                  */
    1532                 :          0 :                                 new_n->slots[slot] = ptr;
    1533                 :          0 :                         continue;
    1534                 :            :                 }
    1535                 :            : 
    1536                 :          0 :                 new_ptr_pp = &new_n->slots[slot];
    1537                 :          0 :                 cursor = ptr;
    1538                 :          0 :                 goto descend;
    1539                 :            :         }
    1540                 :            : 
    1541                 :            :         pr_devel("-- compress node %p --\n", new_n);
    1542                 :            : 
    1543                 :            :         /* Count up the number of empty slots in this node and work out the
    1544                 :            :          * subtree leaf count.
    1545                 :            :          */
    1546                 :          0 :         new_n->nr_leaves_on_branch = 0;
    1547                 :            :         nr_free = 0;
    1548         [ #  # ]:          0 :         for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
    1549                 :          0 :                 ptr = new_n->slots[slot];
    1550         [ #  # ]:          0 :                 if (!ptr)
    1551                 :          0 :                         nr_free++;
    1552         [ #  # ]:          0 :                 else if (assoc_array_ptr_is_leaf(ptr))
    1553                 :          0 :                         new_n->nr_leaves_on_branch++;
    1554                 :            :         }
    1555                 :            :         pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch);
    1556                 :            : 
    1557                 :            :         /* See what we can fold in */
    1558                 :            :         next_slot = 0;
    1559         [ #  # ]:          0 :         for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
    1560                 :            :                 struct assoc_array_shortcut *s;
    1561                 :            :                 struct assoc_array_node *child;
    1562                 :            : 
    1563                 :          0 :                 ptr = new_n->slots[slot];
    1564   [ #  #  #  # ]:          0 :                 if (!ptr || assoc_array_ptr_is_leaf(ptr))
    1565                 :          0 :                         continue;
    1566                 :            : 
    1567                 :            :                 s = NULL;
    1568         [ #  # ]:          0 :                 if (assoc_array_ptr_is_shortcut(ptr)) {
    1569                 :            :                         s = assoc_array_ptr_to_shortcut(ptr);
    1570                 :          0 :                         ptr = s->next_node;
    1571                 :            :                 }
    1572                 :            : 
    1573                 :            :                 child = assoc_array_ptr_to_node(ptr);
    1574                 :          0 :                 new_n->nr_leaves_on_branch += child->nr_leaves_on_branch;
    1575                 :            : 
    1576         [ #  # ]:          0 :                 if (child->nr_leaves_on_branch <= nr_free + 1) {
    1577                 :            :                         /* Fold the child node into this one */
    1578                 :            :                         pr_devel("[%d] fold node %lu/%d [nx %d]\n",
    1579                 :            :                                  slot, child->nr_leaves_on_branch, nr_free + 1,
    1580                 :            :                                  next_slot);
    1581                 :            : 
    1582                 :            :                         /* We would already have reaped an intervening shortcut
    1583                 :            :                          * on the way back up the tree.
    1584                 :            :                          */
    1585         [ #  # ]:          0 :                         BUG_ON(s);
    1586                 :            : 
    1587                 :          0 :                         new_n->slots[slot] = NULL;
    1588                 :            :                         nr_free++;
    1589         [ #  # ]:          0 :                         if (slot < next_slot)
    1590                 :            :                                 next_slot = slot;
    1591         [ #  # ]:          0 :                         for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) {
    1592                 :          0 :                                 struct assoc_array_ptr *p = child->slots[i];
    1593         [ #  # ]:          0 :                                 if (!p)
    1594                 :          0 :                                         continue;
    1595         [ #  # ]:          0 :                                 BUG_ON(assoc_array_ptr_is_meta(p));
    1596         [ #  # ]:          0 :                                 while (new_n->slots[next_slot])
    1597                 :          0 :                                         next_slot++;
    1598         [ #  # ]:          0 :                                 BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT);
    1599                 :          0 :                                 new_n->slots[next_slot++] = p;
    1600                 :          0 :                                 nr_free--;
    1601                 :            :                         }
    1602                 :          0 :                         kfree(child);
    1603                 :            :                 } else {
    1604                 :            :                         pr_devel("[%d] retain node %lu/%d [nx %d]\n",
    1605                 :            :                                  slot, child->nr_leaves_on_branch, nr_free + 1,
    1606                 :            :                                  next_slot);
    1607                 :            :                 }
    1608                 :            :         }
    1609                 :            : 
    1610                 :            :         pr_devel("after: %lu\n", new_n->nr_leaves_on_branch);
    1611                 :            : 
    1612                 :          0 :         nr_leaves_on_tree = new_n->nr_leaves_on_branch;
    1613                 :            : 
    1614                 :            :         /* Excise this node if it is singly occupied by a shortcut */
    1615         [ #  # ]:          0 :         if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) {
    1616         [ #  # ]:          0 :                 for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++)
    1617         [ #  # ]:          0 :                         if ((ptr = new_n->slots[slot]))
    1618                 :            :                                 break;
    1619                 :            : 
    1620   [ #  #  #  # ]:          0 :                 if (assoc_array_ptr_is_meta(ptr) &&
    1621                 :            :                     assoc_array_ptr_is_shortcut(ptr)) {
    1622                 :            :                         pr_devel("excise node %p with 1 shortcut\n", new_n);
    1623                 :            :                         new_s = assoc_array_ptr_to_shortcut(ptr);
    1624                 :          0 :                         new_parent = new_n->back_pointer;
    1625                 :          0 :                         slot = new_n->parent_slot;
    1626                 :          0 :                         kfree(new_n);
    1627         [ #  # ]:          0 :                         if (!new_parent) {
    1628                 :          0 :                                 new_s->back_pointer = NULL;
    1629                 :          0 :                                 new_s->parent_slot = 0;
    1630                 :          0 :                                 new_root = ptr;
    1631                 :          0 :                                 goto gc_complete;
    1632                 :            :                         }
    1633                 :            : 
    1634         [ #  # ]:          0 :                         if (assoc_array_ptr_is_shortcut(new_parent)) {
    1635                 :            :                                 /* We can discard any preceding shortcut also */
    1636                 :            :                                 struct assoc_array_shortcut *s =
    1637                 :            :                                         assoc_array_ptr_to_shortcut(new_parent);
    1638                 :            : 
    1639                 :            :                                 pr_devel("excise preceding shortcut\n");
    1640                 :            : 
    1641                 :          0 :                                 new_parent = new_s->back_pointer = s->back_pointer;
    1642                 :          0 :                                 slot = new_s->parent_slot = s->parent_slot;
    1643                 :          0 :                                 kfree(s);
    1644         [ #  # ]:          0 :                                 if (!new_parent) {
    1645                 :          0 :                                         new_s->back_pointer = NULL;
    1646                 :          0 :                                         new_s->parent_slot = 0;
    1647                 :          0 :                                         new_root = ptr;
    1648                 :          0 :                                         goto gc_complete;
    1649                 :            :                                 }
    1650                 :            :                         }
    1651                 :            : 
    1652                 :          0 :                         new_s->back_pointer = new_parent;
    1653                 :          0 :                         new_s->parent_slot = slot;
    1654                 :            :                         new_n = assoc_array_ptr_to_node(new_parent);
    1655                 :          0 :                         new_n->slots[slot] = ptr;
    1656                 :          0 :                         goto ascend_old_tree;
    1657                 :            :                 }
    1658                 :            :         }
    1659                 :            : 
    1660                 :            :         /* Excise any shortcuts we might encounter that point to nodes that
    1661                 :            :          * only contain leaves.
    1662                 :            :          */
    1663                 :          0 :         ptr = new_n->back_pointer;
    1664         [ #  # ]:          0 :         if (!ptr)
    1665                 :            :                 goto gc_complete;
    1666                 :            : 
    1667         [ #  # ]:          0 :         if (assoc_array_ptr_is_shortcut(ptr)) {
    1668                 :            :                 new_s = assoc_array_ptr_to_shortcut(ptr);
    1669                 :          0 :                 new_parent = new_s->back_pointer;
    1670                 :          0 :                 slot = new_s->parent_slot;
    1671                 :            : 
    1672         [ #  # ]:          0 :                 if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) {
    1673                 :            :                         struct assoc_array_node *n;
    1674                 :            : 
    1675                 :            :                         pr_devel("excise shortcut\n");
    1676                 :          0 :                         new_n->back_pointer = new_parent;
    1677                 :          0 :                         new_n->parent_slot = slot;
    1678                 :          0 :                         kfree(new_s);
    1679         [ #  # ]:          0 :                         if (!new_parent) {
    1680                 :          0 :                                 new_root = assoc_array_node_to_ptr(new_n);
    1681                 :          0 :                                 goto gc_complete;
    1682                 :            :                         }
    1683                 :            : 
    1684                 :            :                         n = assoc_array_ptr_to_node(new_parent);
    1685                 :          0 :                         n->slots[slot] = assoc_array_node_to_ptr(new_n);
    1686                 :            :                 }
    1687                 :            :         } else {
    1688                 :            :                 new_parent = ptr;
    1689                 :            :         }
    1690                 :            :         new_n = assoc_array_ptr_to_node(new_parent);
    1691                 :            : 
    1692                 :            : ascend_old_tree:
    1693                 :          0 :         ptr = node->back_pointer;
    1694         [ #  # ]:          0 :         if (assoc_array_ptr_is_shortcut(ptr)) {
    1695                 :            :                 shortcut = assoc_array_ptr_to_shortcut(ptr);
    1696                 :          0 :                 slot = shortcut->parent_slot;
    1697                 :          0 :                 cursor = shortcut->back_pointer;
    1698         [ #  # ]:          0 :                 if (!cursor)
    1699                 :            :                         goto gc_complete;
    1700                 :            :         } else {
    1701                 :          0 :                 slot = node->parent_slot;
    1702                 :            :                 cursor = ptr;
    1703                 :            :         }
    1704         [ #  # ]:          0 :         BUG_ON(!cursor);
    1705                 :            :         node = assoc_array_ptr_to_node(cursor);
    1706                 :          0 :         slot++;
    1707                 :          0 :         goto continue_node;
    1708                 :            : 
    1709                 :            : gc_complete:
    1710                 :          0 :         edit->set[0].to = new_root;
    1711                 :          0 :         assoc_array_apply_edit(edit);
    1712                 :          0 :         array->nr_leaves_on_tree = nr_leaves_on_tree;
    1713                 :          0 :         return 0;
    1714                 :            : 
    1715                 :            : enomem:
    1716                 :            :         pr_devel("enomem\n");
    1717                 :          0 :         assoc_array_destroy_subtree(new_root, edit->ops);
    1718                 :          0 :         kfree(edit);
    1719                 :          0 :         return -ENOMEM;
    1720                 :            : }

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