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       1                 :            : // SPDX-License-Identifier: GPL-2.0-only
       2                 :            : /*
       3                 :            :  * Cleancache frontend
       4                 :            :  *
       5                 :            :  * This code provides the generic "frontend" layer to call a matching
       6                 :            :  * "backend" driver implementation of cleancache.  See
       7                 :            :  * Documentation/vm/cleancache.rst for more information.
       8                 :            :  *
       9                 :            :  * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
      10                 :            :  * Author: Dan Magenheimer
      11                 :            :  */
      12                 :            : 
      13                 :            : #include <linux/module.h>
      14                 :            : #include <linux/fs.h>
      15                 :            : #include <linux/exportfs.h>
      16                 :            : #include <linux/mm.h>
      17                 :            : #include <linux/debugfs.h>
      18                 :            : #include <linux/cleancache.h>
      19                 :            : 
      20                 :            : /*
      21                 :            :  * cleancache_ops is set by cleancache_register_ops to contain the pointers
      22                 :            :  * to the cleancache "backend" implementation functions.
      23                 :            :  */
      24                 :            : static const struct cleancache_ops *cleancache_ops __read_mostly;
      25                 :            : 
      26                 :            : /*
      27                 :            :  * Counters available via /sys/kernel/debug/cleancache (if debugfs is
      28                 :            :  * properly configured.  These are for information only so are not protected
      29                 :            :  * against increment races.
      30                 :            :  */
      31                 :            : static u64 cleancache_succ_gets;
      32                 :            : static u64 cleancache_failed_gets;
      33                 :            : static u64 cleancache_puts;
      34                 :            : static u64 cleancache_invalidates;
      35                 :            : 
      36                 :          0 : static void cleancache_register_ops_sb(struct super_block *sb, void *unused)
      37                 :            : {
      38                 :          0 :         switch (sb->cleancache_poolid) {
      39                 :            :         case CLEANCACHE_NO_BACKEND:
      40                 :            :                 __cleancache_init_fs(sb);
      41                 :            :                 break;
      42                 :            :         case CLEANCACHE_NO_BACKEND_SHARED:
      43                 :            :                 __cleancache_init_shared_fs(sb);
      44                 :            :                 break;
      45                 :            :         }
      46                 :          0 : }
      47                 :            : 
      48                 :            : /*
      49                 :            :  * Register operations for cleancache. Returns 0 on success.
      50                 :            :  */
      51                 :          0 : int cleancache_register_ops(const struct cleancache_ops *ops)
      52                 :            : {
      53                 :          0 :         if (cmpxchg(&cleancache_ops, NULL, ops))
      54                 :            :                 return -EBUSY;
      55                 :            : 
      56                 :            :         /*
      57                 :            :          * A cleancache backend can be built as a module and hence loaded after
      58                 :            :          * a cleancache enabled filesystem has called cleancache_init_fs. To
      59                 :            :          * handle such a scenario, here we call ->init_fs or ->init_shared_fs
      60                 :            :          * for each active super block. To differentiate between local and
      61                 :            :          * shared filesystems, we temporarily initialize sb->cleancache_poolid
      62                 :            :          * to CLEANCACHE_NO_BACKEND or CLEANCACHE_NO_BACKEND_SHARED
      63                 :            :          * respectively in case there is no backend registered at the time
      64                 :            :          * cleancache_init_fs or cleancache_init_shared_fs is called.
      65                 :            :          *
      66                 :            :          * Since filesystems can be mounted concurrently with cleancache
      67                 :            :          * backend registration, we have to be careful to guarantee that all
      68                 :            :          * cleancache enabled filesystems that has been mounted by the time
      69                 :            :          * cleancache_register_ops is called has got and all mounted later will
      70                 :            :          * get cleancache_poolid. This is assured by the following statements
      71                 :            :          * tied together:
      72                 :            :          *
      73                 :            :          * a) iterate_supers skips only those super blocks that has started
      74                 :            :          *    ->kill_sb
      75                 :            :          *
      76                 :            :          * b) if iterate_supers encounters a super block that has not finished
      77                 :            :          *    ->mount yet, it waits until it is finished
      78                 :            :          *
      79                 :            :          * c) cleancache_init_fs is called from ->mount and
      80                 :            :          *    cleancache_invalidate_fs is called from ->kill_sb
      81                 :            :          *
      82                 :            :          * d) we call iterate_supers after cleancache_ops has been set
      83                 :            :          *
      84                 :            :          * From a) it follows that if iterate_supers skips a super block, then
      85                 :            :          * either the super block is already dead, in which case we do not need
      86                 :            :          * to bother initializing cleancache for it, or it was mounted after we
      87                 :            :          * initiated iterate_supers. In the latter case, it must have seen
      88                 :            :          * cleancache_ops set according to d) and initialized cleancache from
      89                 :            :          * ->mount by itself according to c). This proves that we call
      90                 :            :          * ->init_fs at least once for each active super block.
      91                 :            :          *
      92                 :            :          * From b) and c) it follows that if iterate_supers encounters a super
      93                 :            :          * block that has already started ->init_fs, it will wait until ->mount
      94                 :            :          * and hence ->init_fs has finished, then check cleancache_poolid, see
      95                 :            :          * that it has already been set and therefore do nothing. This proves
      96                 :            :          * that we call ->init_fs no more than once for each super block.
      97                 :            :          *
      98                 :            :          * Combined together, the last two paragraphs prove the function
      99                 :            :          * correctness.
     100                 :            :          *
     101                 :            :          * Note that various cleancache callbacks may proceed before this
     102                 :            :          * function is called or even concurrently with it, but since
     103                 :            :          * CLEANCACHE_NO_BACKEND is negative, they will all result in a noop
     104                 :            :          * until the corresponding ->init_fs has been actually called and
     105                 :            :          * cleancache_ops has been set.
     106                 :            :          */
     107                 :          0 :         iterate_supers(cleancache_register_ops_sb, NULL);
     108                 :          0 :         return 0;
     109                 :            : }
     110                 :            : EXPORT_SYMBOL(cleancache_register_ops);
     111                 :            : 
     112                 :            : /* Called by a cleancache-enabled filesystem at time of mount */
     113                 :          3 : void __cleancache_init_fs(struct super_block *sb)
     114                 :            : {
     115                 :            :         int pool_id = CLEANCACHE_NO_BACKEND;
     116                 :            : 
     117                 :          3 :         if (cleancache_ops) {
     118                 :          0 :                 pool_id = cleancache_ops->init_fs(PAGE_SIZE);
     119                 :          0 :                 if (pool_id < 0)
     120                 :            :                         pool_id = CLEANCACHE_NO_POOL;
     121                 :            :         }
     122                 :          3 :         sb->cleancache_poolid = pool_id;
     123                 :          3 : }
     124                 :            : EXPORT_SYMBOL(__cleancache_init_fs);
     125                 :            : 
     126                 :            : /* Called by a cleancache-enabled clustered filesystem at time of mount */
     127                 :          0 : void __cleancache_init_shared_fs(struct super_block *sb)
     128                 :            : {
     129                 :            :         int pool_id = CLEANCACHE_NO_BACKEND_SHARED;
     130                 :            : 
     131                 :          0 :         if (cleancache_ops) {
     132                 :          0 :                 pool_id = cleancache_ops->init_shared_fs(&sb->s_uuid, PAGE_SIZE);
     133                 :          0 :                 if (pool_id < 0)
     134                 :            :                         pool_id = CLEANCACHE_NO_POOL;
     135                 :            :         }
     136                 :          0 :         sb->cleancache_poolid = pool_id;
     137                 :          0 : }
     138                 :            : EXPORT_SYMBOL(__cleancache_init_shared_fs);
     139                 :            : 
     140                 :            : /*
     141                 :            :  * If the filesystem uses exportable filehandles, use the filehandle as
     142                 :            :  * the key, else use the inode number.
     143                 :            :  */
     144                 :          0 : static int cleancache_get_key(struct inode *inode,
     145                 :            :                               struct cleancache_filekey *key)
     146                 :            : {
     147                 :            :         int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
     148                 :          0 :         int len = 0, maxlen = CLEANCACHE_KEY_MAX;
     149                 :          0 :         struct super_block *sb = inode->i_sb;
     150                 :            : 
     151                 :          0 :         key->u.ino = inode->i_ino;
     152                 :          0 :         if (sb->s_export_op != NULL) {
     153                 :          0 :                 fhfn = sb->s_export_op->encode_fh;
     154                 :          0 :                 if  (fhfn) {
     155                 :          0 :                         len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
     156                 :          0 :                         if (len <= FILEID_ROOT || len == FILEID_INVALID)
     157                 :            :                                 return -1;
     158                 :          0 :                         if (maxlen > CLEANCACHE_KEY_MAX)
     159                 :            :                                 return -1;
     160                 :            :                 }
     161                 :            :         }
     162                 :            :         return 0;
     163                 :            : }
     164                 :            : 
     165                 :            : /*
     166                 :            :  * "Get" data from cleancache associated with the poolid/inode/index
     167                 :            :  * that were specified when the data was put to cleanache and, if
     168                 :            :  * successful, use it to fill the specified page with data and return 0.
     169                 :            :  * The pageframe is unchanged and returns -1 if the get fails.
     170                 :            :  * Page must be locked by caller.
     171                 :            :  *
     172                 :            :  * The function has two checks before any action is taken - whether
     173                 :            :  * a backend is registered and whether the sb->cleancache_poolid
     174                 :            :  * is correct.
     175                 :            :  */
     176                 :          0 : int __cleancache_get_page(struct page *page)
     177                 :            : {
     178                 :            :         int ret = -1;
     179                 :            :         int pool_id;
     180                 :          0 :         struct cleancache_filekey key = { .u.key = { 0 } };
     181                 :            : 
     182                 :          0 :         if (!cleancache_ops) {
     183                 :          0 :                 cleancache_failed_gets++;
     184                 :          0 :                 goto out;
     185                 :            :         }
     186                 :            : 
     187                 :            :         VM_BUG_ON_PAGE(!PageLocked(page), page);
     188                 :          0 :         pool_id = page->mapping->host->i_sb->cleancache_poolid;
     189                 :          0 :         if (pool_id < 0)
     190                 :            :                 goto out;
     191                 :            : 
     192                 :          0 :         if (cleancache_get_key(page->mapping->host, &key) < 0)
     193                 :            :                 goto out;
     194                 :            : 
     195                 :          0 :         ret = cleancache_ops->get_page(pool_id, key, page->index, page);
     196                 :          0 :         if (ret == 0)
     197                 :          0 :                 cleancache_succ_gets++;
     198                 :            :         else
     199                 :          0 :                 cleancache_failed_gets++;
     200                 :            : out:
     201                 :          0 :         return ret;
     202                 :            : }
     203                 :            : EXPORT_SYMBOL(__cleancache_get_page);
     204                 :            : 
     205                 :            : /*
     206                 :            :  * "Put" data from a page to cleancache and associate it with the
     207                 :            :  * (previously-obtained per-filesystem) poolid and the page's,
     208                 :            :  * inode and page index.  Page must be locked.  Note that a put_page
     209                 :            :  * always "succeeds", though a subsequent get_page may succeed or fail.
     210                 :            :  *
     211                 :            :  * The function has two checks before any action is taken - whether
     212                 :            :  * a backend is registered and whether the sb->cleancache_poolid
     213                 :            :  * is correct.
     214                 :            :  */
     215                 :          0 : void __cleancache_put_page(struct page *page)
     216                 :            : {
     217                 :            :         int pool_id;
     218                 :          0 :         struct cleancache_filekey key = { .u.key = { 0 } };
     219                 :            : 
     220                 :          0 :         if (!cleancache_ops) {
     221                 :          0 :                 cleancache_puts++;
     222                 :          0 :                 return;
     223                 :            :         }
     224                 :            : 
     225                 :            :         VM_BUG_ON_PAGE(!PageLocked(page), page);
     226                 :          0 :         pool_id = page->mapping->host->i_sb->cleancache_poolid;
     227                 :          0 :         if (pool_id >= 0 &&
     228                 :          0 :                 cleancache_get_key(page->mapping->host, &key) >= 0) {
     229                 :          0 :                 cleancache_ops->put_page(pool_id, key, page->index, page);
     230                 :          0 :                 cleancache_puts++;
     231                 :            :         }
     232                 :            : }
     233                 :            : EXPORT_SYMBOL(__cleancache_put_page);
     234                 :            : 
     235                 :            : /*
     236                 :            :  * Invalidate any data from cleancache associated with the poolid and the
     237                 :            :  * page's inode and page index so that a subsequent "get" will fail.
     238                 :            :  *
     239                 :            :  * The function has two checks before any action is taken - whether
     240                 :            :  * a backend is registered and whether the sb->cleancache_poolid
     241                 :            :  * is correct.
     242                 :            :  */
     243                 :          0 : void __cleancache_invalidate_page(struct address_space *mapping,
     244                 :            :                                         struct page *page)
     245                 :            : {
     246                 :            :         /* careful... page->mapping is NULL sometimes when this is called */
     247                 :          0 :         int pool_id = mapping->host->i_sb->cleancache_poolid;
     248                 :          0 :         struct cleancache_filekey key = { .u.key = { 0 } };
     249                 :            : 
     250                 :          0 :         if (!cleancache_ops)
     251                 :          0 :                 return;
     252                 :            : 
     253                 :          0 :         if (pool_id >= 0) {
     254                 :            :                 VM_BUG_ON_PAGE(!PageLocked(page), page);
     255                 :          0 :                 if (cleancache_get_key(mapping->host, &key) >= 0) {
     256                 :          0 :                         cleancache_ops->invalidate_page(pool_id,
     257                 :            :                                         key, page->index);
     258                 :          0 :                         cleancache_invalidates++;
     259                 :            :                 }
     260                 :            :         }
     261                 :            : }
     262                 :            : EXPORT_SYMBOL(__cleancache_invalidate_page);
     263                 :            : 
     264                 :            : /*
     265                 :            :  * Invalidate all data from cleancache associated with the poolid and the
     266                 :            :  * mappings's inode so that all subsequent gets to this poolid/inode
     267                 :            :  * will fail.
     268                 :            :  *
     269                 :            :  * The function has two checks before any action is taken - whether
     270                 :            :  * a backend is registered and whether the sb->cleancache_poolid
     271                 :            :  * is correct.
     272                 :            :  */
     273                 :          0 : void __cleancache_invalidate_inode(struct address_space *mapping)
     274                 :            : {
     275                 :          0 :         int pool_id = mapping->host->i_sb->cleancache_poolid;
     276                 :          0 :         struct cleancache_filekey key = { .u.key = { 0 } };
     277                 :            : 
     278                 :          0 :         if (!cleancache_ops)
     279                 :          0 :                 return;
     280                 :            : 
     281                 :          0 :         if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
     282                 :          0 :                 cleancache_ops->invalidate_inode(pool_id, key);
     283                 :            : }
     284                 :            : EXPORT_SYMBOL(__cleancache_invalidate_inode);
     285                 :            : 
     286                 :            : /*
     287                 :            :  * Called by any cleancache-enabled filesystem at time of unmount;
     288                 :            :  * note that pool_id is surrendered and may be returned by a subsequent
     289                 :            :  * cleancache_init_fs or cleancache_init_shared_fs.
     290                 :            :  */
     291                 :          3 : void __cleancache_invalidate_fs(struct super_block *sb)
     292                 :            : {
     293                 :            :         int pool_id;
     294                 :            : 
     295                 :          3 :         pool_id = sb->cleancache_poolid;
     296                 :          3 :         sb->cleancache_poolid = CLEANCACHE_NO_POOL;
     297                 :            : 
     298                 :          3 :         if (cleancache_ops && pool_id >= 0)
     299                 :          0 :                 cleancache_ops->invalidate_fs(pool_id);
     300                 :          3 : }
     301                 :            : EXPORT_SYMBOL(__cleancache_invalidate_fs);
     302                 :            : 
     303                 :          3 : static int __init init_cleancache(void)
     304                 :            : {
     305                 :            : #ifdef CONFIG_DEBUG_FS
     306                 :          3 :         struct dentry *root = debugfs_create_dir("cleancache", NULL);
     307                 :            : 
     308                 :          3 :         debugfs_create_u64("succ_gets", 0444, root, &cleancache_succ_gets);
     309                 :          3 :         debugfs_create_u64("failed_gets", 0444, root, &cleancache_failed_gets);
     310                 :          3 :         debugfs_create_u64("puts", 0444, root, &cleancache_puts);
     311                 :          3 :         debugfs_create_u64("invalidates", 0444, root, &cleancache_invalidates);
     312                 :            : #endif
     313                 :          3 :         return 0;
     314                 :            : }
     315                 :            : module_init(init_cleancache)