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       1                 :            : /* SPDX-License-Identifier: GPL-2.0 */
       2                 :            : #ifndef __LINUX_DCACHE_H
       3                 :            : #define __LINUX_DCACHE_H
       4                 :            : 
       5                 :            : #include <linux/atomic.h>
       6                 :            : #include <linux/list.h>
       7                 :            : #include <linux/rculist.h>
       8                 :            : #include <linux/rculist_bl.h>
       9                 :            : #include <linux/spinlock.h>
      10                 :            : #include <linux/seqlock.h>
      11                 :            : #include <linux/cache.h>
      12                 :            : #include <linux/rcupdate.h>
      13                 :            : #include <linux/lockref.h>
      14                 :            : #include <linux/stringhash.h>
      15                 :            : #include <linux/wait.h>
      16                 :            : 
      17                 :            : struct path;
      18                 :            : struct vfsmount;
      19                 :            : 
      20                 :            : /*
      21                 :            :  * linux/include/linux/dcache.h
      22                 :            :  *
      23                 :            :  * Dirent cache data structures
      24                 :            :  *
      25                 :            :  * (C) Copyright 1997 Thomas Schoebel-Theuer,
      26                 :            :  * with heavy changes by Linus Torvalds
      27                 :            :  */
      28                 :            : 
      29                 :            : #define IS_ROOT(x) ((x) == (x)->d_parent)
      30                 :            : 
      31                 :            : /* The hash is always the low bits of hash_len */
      32                 :            : #ifdef __LITTLE_ENDIAN
      33                 :            :  #define HASH_LEN_DECLARE u32 hash; u32 len
      34                 :            :  #define bytemask_from_count(cnt)       (~(~0ul << (cnt)*8))
      35                 :            : #else
      36                 :            :  #define HASH_LEN_DECLARE u32 len; u32 hash
      37                 :            :  #define bytemask_from_count(cnt)       (~(~0ul >> (cnt)*8))
      38                 :            : #endif
      39                 :            : 
      40                 :            : /*
      41                 :            :  * "quick string" -- eases parameter passing, but more importantly
      42                 :            :  * saves "metadata" about the string (ie length and the hash).
      43                 :            :  *
      44                 :            :  * hash comes first so it snuggles against d_parent in the
      45                 :            :  * dentry.
      46                 :            :  */
      47                 :            : struct qstr {
      48                 :            :         union {
      49                 :            :                 struct {
      50                 :            :                         HASH_LEN_DECLARE;
      51                 :            :                 };
      52                 :            :                 u64 hash_len;
      53                 :            :         };
      54                 :            :         const unsigned char *name;
      55                 :            : };
      56                 :            : 
      57                 :            : #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
      58                 :            : 
      59                 :            : extern const struct qstr empty_name;
      60                 :            : extern const struct qstr slash_name;
      61                 :            : 
      62                 :            : struct dentry_stat_t {
      63                 :            :         long nr_dentry;
      64                 :            :         long nr_unused;
      65                 :            :         long age_limit;         /* age in seconds */
      66                 :            :         long want_pages;        /* pages requested by system */
      67                 :            :         long nr_negative;       /* # of unused negative dentries */
      68                 :            :         long dummy;             /* Reserved for future use */
      69                 :            : };
      70                 :            : extern struct dentry_stat_t dentry_stat;
      71                 :            : 
      72                 :            : /*
      73                 :            :  * Try to keep struct dentry aligned on 64 byte cachelines (this will
      74                 :            :  * give reasonable cacheline footprint with larger lines without the
      75                 :            :  * large memory footprint increase).
      76                 :            :  */
      77                 :            : #ifdef CONFIG_64BIT
      78                 :            : # define DNAME_INLINE_LEN 32 /* 192 bytes */
      79                 :            : #else
      80                 :            : # ifdef CONFIG_SMP
      81                 :            : #  define DNAME_INLINE_LEN 36 /* 128 bytes */
      82                 :            : # else
      83                 :            : #  define DNAME_INLINE_LEN 40 /* 128 bytes */
      84                 :            : # endif
      85                 :            : #endif
      86                 :            : 
      87                 :            : #define d_lock  d_lockref.lock
      88                 :            : 
      89                 :            : struct dentry {
      90                 :            :         /* RCU lookup touched fields */
      91                 :            :         unsigned int d_flags;           /* protected by d_lock */
      92                 :            :         seqcount_t d_seq;               /* per dentry seqlock */
      93                 :            :         struct hlist_bl_node d_hash;    /* lookup hash list */
      94                 :            :         struct dentry *d_parent;        /* parent directory */
      95                 :            :         struct qstr d_name;
      96                 :            :         struct inode *d_inode;          /* Where the name belongs to - NULL is
      97                 :            :                                          * negative */
      98                 :            :         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
      99                 :            : 
     100                 :            :         /* Ref lookup also touches following */
     101                 :            :         struct lockref d_lockref;       /* per-dentry lock and refcount */
     102                 :            :         const struct dentry_operations *d_op;
     103                 :            :         struct super_block *d_sb;       /* The root of the dentry tree */
     104                 :            :         unsigned long d_time;           /* used by d_revalidate */
     105                 :            :         void *d_fsdata;                 /* fs-specific data */
     106                 :            : 
     107                 :            :         union {
     108                 :            :                 struct list_head d_lru;         /* LRU list */
     109                 :            :                 wait_queue_head_t *d_wait;      /* in-lookup ones only */
     110                 :            :         };
     111                 :            :         struct list_head d_child;       /* child of parent list */
     112                 :            :         struct list_head d_subdirs;     /* our children */
     113                 :            :         /*
     114                 :            :          * d_alias and d_rcu can share memory
     115                 :            :          */
     116                 :            :         union {
     117                 :            :                 struct hlist_node d_alias;      /* inode alias list */
     118                 :            :                 struct hlist_bl_node d_in_lookup_hash;  /* only for in-lookup ones */
     119                 :            :                 struct rcu_head d_rcu;
     120                 :            :         } d_u;
     121                 :            : } __randomize_layout;
     122                 :            : 
     123                 :            : /*
     124                 :            :  * dentry->d_lock spinlock nesting subclasses:
     125                 :            :  *
     126                 :            :  * 0: normal
     127                 :            :  * 1: nested
     128                 :            :  */
     129                 :            : enum dentry_d_lock_class
     130                 :            : {
     131                 :            :         DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
     132                 :            :         DENTRY_D_LOCK_NESTED
     133                 :            : };
     134                 :            : 
     135                 :            : struct dentry_operations {
     136                 :            :         int (*d_revalidate)(struct dentry *, unsigned int);
     137                 :            :         int (*d_weak_revalidate)(struct dentry *, unsigned int);
     138                 :            :         int (*d_hash)(const struct dentry *, struct qstr *);
     139                 :            :         int (*d_compare)(const struct dentry *,
     140                 :            :                         unsigned int, const char *, const struct qstr *);
     141                 :            :         int (*d_delete)(const struct dentry *);
     142                 :            :         int (*d_init)(struct dentry *);
     143                 :            :         void (*d_release)(struct dentry *);
     144                 :            :         void (*d_prune)(struct dentry *);
     145                 :            :         void (*d_iput)(struct dentry *, struct inode *);
     146                 :            :         char *(*d_dname)(struct dentry *, char *, int);
     147                 :            :         struct vfsmount *(*d_automount)(struct path *);
     148                 :            :         int (*d_manage)(const struct path *, bool);
     149                 :            :         struct dentry *(*d_real)(struct dentry *, const struct inode *);
     150                 :            : } ____cacheline_aligned;
     151                 :            : 
     152                 :            : /*
     153                 :            :  * Locking rules for dentry_operations callbacks are to be found in
     154                 :            :  * Documentation/filesystems/locking.rst. Keep it updated!
     155                 :            :  *
     156                 :            :  * FUrther descriptions are found in Documentation/filesystems/vfs.rst.
     157                 :            :  * Keep it updated too!
     158                 :            :  */
     159                 :            : 
     160                 :            : /* d_flags entries */
     161                 :            : #define DCACHE_OP_HASH                  0x00000001
     162                 :            : #define DCACHE_OP_COMPARE               0x00000002
     163                 :            : #define DCACHE_OP_REVALIDATE            0x00000004
     164                 :            : #define DCACHE_OP_DELETE                0x00000008
     165                 :            : #define DCACHE_OP_PRUNE                 0x00000010
     166                 :            : 
     167                 :            : #define DCACHE_DISCONNECTED             0x00000020
     168                 :            :      /* This dentry is possibly not currently connected to the dcache tree, in
     169                 :            :       * which case its parent will either be itself, or will have this flag as
     170                 :            :       * well.  nfsd will not use a dentry with this bit set, but will first
     171                 :            :       * endeavour to clear the bit either by discovering that it is connected,
     172                 :            :       * or by performing lookup operations.   Any filesystem which supports
     173                 :            :       * nfsd_operations MUST have a lookup function which, if it finds a
     174                 :            :       * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
     175                 :            :       * dentry into place and return that dentry rather than the passed one,
     176                 :            :       * typically using d_splice_alias. */
     177                 :            : 
     178                 :            : #define DCACHE_REFERENCED               0x00000040 /* Recently used, don't discard. */
     179                 :            : 
     180                 :            : #define DCACHE_CANT_MOUNT               0x00000100
     181                 :            : #define DCACHE_GENOCIDE                 0x00000200
     182                 :            : #define DCACHE_SHRINK_LIST              0x00000400
     183                 :            : 
     184                 :            : #define DCACHE_OP_WEAK_REVALIDATE       0x00000800
     185                 :            : 
     186                 :            : #define DCACHE_NFSFS_RENAMED            0x00001000
     187                 :            :      /* this dentry has been "silly renamed" and has to be deleted on the last
     188                 :            :       * dput() */
     189                 :            : #define DCACHE_COOKIE                   0x00002000 /* For use by dcookie subsystem */
     190                 :            : #define DCACHE_FSNOTIFY_PARENT_WATCHED  0x00004000
     191                 :            :      /* Parent inode is watched by some fsnotify listener */
     192                 :            : 
     193                 :            : #define DCACHE_DENTRY_KILLED            0x00008000
     194                 :            : 
     195                 :            : #define DCACHE_MOUNTED                  0x00010000 /* is a mountpoint */
     196                 :            : #define DCACHE_NEED_AUTOMOUNT           0x00020000 /* handle automount on this dir */
     197                 :            : #define DCACHE_MANAGE_TRANSIT           0x00040000 /* manage transit from this dirent */
     198                 :            : #define DCACHE_MANAGED_DENTRY \
     199                 :            :         (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
     200                 :            : 
     201                 :            : #define DCACHE_LRU_LIST                 0x00080000
     202                 :            : 
     203                 :            : #define DCACHE_ENTRY_TYPE               0x00700000
     204                 :            : #define DCACHE_MISS_TYPE                0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
     205                 :            : #define DCACHE_WHITEOUT_TYPE            0x00100000 /* Whiteout dentry (stop pathwalk) */
     206                 :            : #define DCACHE_DIRECTORY_TYPE           0x00200000 /* Normal directory */
     207                 :            : #define DCACHE_AUTODIR_TYPE             0x00300000 /* Lookupless directory (presumed automount) */
     208                 :            : #define DCACHE_REGULAR_TYPE             0x00400000 /* Regular file type (or fallthru to such) */
     209                 :            : #define DCACHE_SPECIAL_TYPE             0x00500000 /* Other file type (or fallthru to such) */
     210                 :            : #define DCACHE_SYMLINK_TYPE             0x00600000 /* Symlink (or fallthru to such) */
     211                 :            : 
     212                 :            : #define DCACHE_MAY_FREE                 0x00800000
     213                 :            : #define DCACHE_FALLTHRU                 0x01000000 /* Fall through to lower layer */
     214                 :            : #define DCACHE_ENCRYPTED_NAME           0x02000000 /* Encrypted name (dir key was unavailable) */
     215                 :            : #define DCACHE_OP_REAL                  0x04000000
     216                 :            : 
     217                 :            : #define DCACHE_PAR_LOOKUP               0x10000000 /* being looked up (with parent locked shared) */
     218                 :            : #define DCACHE_DENTRY_CURSOR            0x20000000
     219                 :            : #define DCACHE_NORCU                    0x40000000 /* No RCU delay for freeing */
     220                 :            : 
     221                 :            : extern seqlock_t rename_lock;
     222                 :            : 
     223                 :            : /*
     224                 :            :  * These are the low-level FS interfaces to the dcache..
     225                 :            :  */
     226                 :            : extern void d_instantiate(struct dentry *, struct inode *);
     227                 :            : extern void d_instantiate_new(struct dentry *, struct inode *);
     228                 :            : extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
     229                 :            : extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
     230                 :            : extern void __d_drop(struct dentry *dentry);
     231                 :            : extern void d_drop(struct dentry *dentry);
     232                 :            : extern void d_delete(struct dentry *);
     233                 :            : extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
     234                 :            : 
     235                 :            : /* allocate/de-allocate */
     236                 :            : extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
     237                 :            : extern struct dentry * d_alloc_anon(struct super_block *);
     238                 :            : extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
     239                 :            :                                         wait_queue_head_t *);
     240                 :            : extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
     241                 :            : extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
     242                 :            : extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
     243                 :            : extern struct dentry *d_find_any_alias(struct inode *inode);
     244                 :            : extern struct dentry * d_obtain_alias(struct inode *);
     245                 :            : extern struct dentry * d_obtain_root(struct inode *);
     246                 :            : extern void shrink_dcache_sb(struct super_block *);
     247                 :            : extern void shrink_dcache_parent(struct dentry *);
     248                 :            : extern void shrink_dcache_for_umount(struct super_block *);
     249                 :            : extern void d_invalidate(struct dentry *);
     250                 :            : 
     251                 :            : /* only used at mount-time */
     252                 :            : extern struct dentry * d_make_root(struct inode *);
     253                 :            : 
     254                 :            : /* <clickety>-<click> the ramfs-type tree */
     255                 :            : extern void d_genocide(struct dentry *);
     256                 :            : 
     257                 :            : extern void d_tmpfile(struct dentry *, struct inode *);
     258                 :            : 
     259                 :            : extern struct dentry *d_find_alias(struct inode *);
     260                 :            : extern void d_prune_aliases(struct inode *);
     261                 :            : 
     262                 :            : /* test whether we have any submounts in a subdir tree */
     263                 :            : extern int path_has_submounts(const struct path *);
     264                 :            : 
     265                 :            : /*
     266                 :            :  * This adds the entry to the hash queues.
     267                 :            :  */
     268                 :            : extern void d_rehash(struct dentry *);
     269                 :            :  
     270                 :            : extern void d_add(struct dentry *, struct inode *);
     271                 :            : 
     272                 :            : /* used for rename() and baskets */
     273                 :            : extern void d_move(struct dentry *, struct dentry *);
     274                 :            : extern void d_exchange(struct dentry *, struct dentry *);
     275                 :            : extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
     276                 :            : 
     277                 :            : /* appendix may either be NULL or be used for transname suffixes */
     278                 :            : extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
     279                 :            : extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
     280                 :            : extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
     281                 :            : extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
     282                 :            :                                 const struct qstr *name, unsigned *seq);
     283                 :            : 
     284                 :            : static inline unsigned d_count(const struct dentry *dentry)
     285                 :            : {
     286                 :          0 :         return dentry->d_lockref.count;
     287                 :            : }
     288                 :            : 
     289                 :            : /*
     290                 :            :  * helper function for dentry_operations.d_dname() members
     291                 :            :  */
     292                 :            : extern __printf(4, 5)
     293                 :            : char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
     294                 :            : 
     295                 :            : extern char *__d_path(const struct path *, const struct path *, char *, int);
     296                 :            : extern char *d_absolute_path(const struct path *, char *, int);
     297                 :            : extern char *d_path(const struct path *, char *, int);
     298                 :            : extern char *dentry_path_raw(struct dentry *, char *, int);
     299                 :            : extern char *dentry_path(struct dentry *, char *, int);
     300                 :            : 
     301                 :            : /* Allocation counts.. */
     302                 :            : 
     303                 :            : /**
     304                 :            :  *      dget, dget_dlock -      get a reference to a dentry
     305                 :            :  *      @dentry: dentry to get a reference to
     306                 :            :  *
     307                 :            :  *      Given a dentry or %NULL pointer increment the reference count
     308                 :            :  *      if appropriate and return the dentry. A dentry will not be 
     309                 :            :  *      destroyed when it has references.
     310                 :            :  */
     311                 :            : static inline struct dentry *dget_dlock(struct dentry *dentry)
     312                 :            : {
     313                 :          3 :         if (dentry)
     314                 :          3 :                 dentry->d_lockref.count++;
     315                 :            :         return dentry;
     316                 :            : }
     317                 :            : 
     318                 :            : static inline struct dentry *dget(struct dentry *dentry)
     319                 :            : {
     320                 :          3 :         if (dentry)
     321                 :          3 :                 lockref_get(&dentry->d_lockref);
     322                 :            :         return dentry;
     323                 :            : }
     324                 :            : 
     325                 :            : extern struct dentry *dget_parent(struct dentry *dentry);
     326                 :            : 
     327                 :            : /**
     328                 :            :  *      d_unhashed -    is dentry hashed
     329                 :            :  *      @dentry: entry to check
     330                 :            :  *
     331                 :            :  *      Returns true if the dentry passed is not currently hashed.
     332                 :            :  */
     333                 :            :  
     334                 :            : static inline int d_unhashed(const struct dentry *dentry)
     335                 :            : {
     336                 :            :         return hlist_bl_unhashed(&dentry->d_hash);
     337                 :            : }
     338                 :            : 
     339                 :            : static inline int d_unlinked(const struct dentry *dentry)
     340                 :            : {
     341                 :          3 :         return d_unhashed(dentry) && !IS_ROOT(dentry);
     342                 :            : }
     343                 :            : 
     344                 :            : static inline int cant_mount(const struct dentry *dentry)
     345                 :            : {
     346                 :          3 :         return (dentry->d_flags & DCACHE_CANT_MOUNT);
     347                 :            : }
     348                 :            : 
     349                 :          3 : static inline void dont_mount(struct dentry *dentry)
     350                 :            : {
     351                 :            :         spin_lock(&dentry->d_lock);
     352                 :          3 :         dentry->d_flags |= DCACHE_CANT_MOUNT;
     353                 :            :         spin_unlock(&dentry->d_lock);
     354                 :          3 : }
     355                 :            : 
     356                 :            : extern void __d_lookup_done(struct dentry *);
     357                 :            : 
     358                 :            : static inline int d_in_lookup(const struct dentry *dentry)
     359                 :            : {
     360                 :          3 :         return dentry->d_flags & DCACHE_PAR_LOOKUP;
     361                 :            : }
     362                 :            : 
     363                 :          3 : static inline void d_lookup_done(struct dentry *dentry)
     364                 :            : {
     365                 :          3 :         if (unlikely(d_in_lookup(dentry))) {
     366                 :            :                 spin_lock(&dentry->d_lock);
     367                 :          3 :                 __d_lookup_done(dentry);
     368                 :            :                 spin_unlock(&dentry->d_lock);
     369                 :            :         }
     370                 :          3 : }
     371                 :            : 
     372                 :            : extern void dput(struct dentry *);
     373                 :            : 
     374                 :            : static inline bool d_managed(const struct dentry *dentry)
     375                 :            : {
     376                 :            :         return dentry->d_flags & DCACHE_MANAGED_DENTRY;
     377                 :            : }
     378                 :            : 
     379                 :            : static inline bool d_mountpoint(const struct dentry *dentry)
     380                 :            : {
     381                 :          3 :         return dentry->d_flags & DCACHE_MOUNTED;
     382                 :            : }
     383                 :            : 
     384                 :            : /*
     385                 :            :  * Directory cache entry type accessor functions.
     386                 :            :  */
     387                 :            : static inline unsigned __d_entry_type(const struct dentry *dentry)
     388                 :            : {
     389                 :          3 :         return dentry->d_flags & DCACHE_ENTRY_TYPE;
     390                 :            : }
     391                 :            : 
     392                 :            : static inline bool d_is_miss(const struct dentry *dentry)
     393                 :            : {
     394                 :          3 :         return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
     395                 :            : }
     396                 :            : 
     397                 :            : static inline bool d_is_whiteout(const struct dentry *dentry)
     398                 :            : {
     399                 :            :         return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
     400                 :            : }
     401                 :            : 
     402                 :            : static inline bool d_can_lookup(const struct dentry *dentry)
     403                 :            : {
     404                 :            :         return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
     405                 :            : }
     406                 :            : 
     407                 :            : static inline bool d_is_autodir(const struct dentry *dentry)
     408                 :            : {
     409                 :            :         return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
     410                 :            : }
     411                 :            : 
     412                 :            : static inline bool d_is_dir(const struct dentry *dentry)
     413                 :            : {
     414                 :          3 :         return d_can_lookup(dentry) || d_is_autodir(dentry);
     415                 :            : }
     416                 :            : 
     417                 :            : static inline bool d_is_symlink(const struct dentry *dentry)
     418                 :            : {
     419                 :            :         return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
     420                 :            : }
     421                 :            : 
     422                 :            : static inline bool d_is_reg(const struct dentry *dentry)
     423                 :            : {
     424                 :            :         return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
     425                 :            : }
     426                 :            : 
     427                 :            : static inline bool d_is_special(const struct dentry *dentry)
     428                 :            : {
     429                 :            :         return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
     430                 :            : }
     431                 :            : 
     432                 :            : static inline bool d_is_file(const struct dentry *dentry)
     433                 :            : {
     434                 :            :         return d_is_reg(dentry) || d_is_special(dentry);
     435                 :            : }
     436                 :            : 
     437                 :            : static inline bool d_is_negative(const struct dentry *dentry)
     438                 :            : {
     439                 :            :         // TODO: check d_is_whiteout(dentry) also.
     440                 :            :         return d_is_miss(dentry);
     441                 :            : }
     442                 :            : 
     443                 :            : static inline bool d_is_positive(const struct dentry *dentry)
     444                 :            : {
     445                 :          3 :         return !d_is_negative(dentry);
     446                 :            : }
     447                 :            : 
     448                 :            : /**
     449                 :            :  * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
     450                 :            :  * @dentry: The dentry in question
     451                 :            :  *
     452                 :            :  * Returns true if the dentry represents either an absent name or a name that
     453                 :            :  * doesn't map to an inode (ie. ->d_inode is NULL).  The dentry could represent
     454                 :            :  * a true miss, a whiteout that isn't represented by a 0,0 chardev or a
     455                 :            :  * fallthrough marker in an opaque directory.
     456                 :            :  *
     457                 :            :  * Note!  (1) This should be used *only* by a filesystem to examine its own
     458                 :            :  * dentries.  It should not be used to look at some other filesystem's
     459                 :            :  * dentries.  (2) It should also be used in combination with d_inode() to get
     460                 :            :  * the inode.  (3) The dentry may have something attached to ->d_lower and the
     461                 :            :  * type field of the flags may be set to something other than miss or whiteout.
     462                 :            :  */
     463                 :            : static inline bool d_really_is_negative(const struct dentry *dentry)
     464                 :            : {
     465                 :          3 :         return dentry->d_inode == NULL;
     466                 :            : }
     467                 :            : 
     468                 :            : /**
     469                 :            :  * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
     470                 :            :  * @dentry: The dentry in question
     471                 :            :  *
     472                 :            :  * Returns true if the dentry represents a name that maps to an inode
     473                 :            :  * (ie. ->d_inode is not NULL).  The dentry might still represent a whiteout if
     474                 :            :  * that is represented on medium as a 0,0 chardev.
     475                 :            :  *
     476                 :            :  * Note!  (1) This should be used *only* by a filesystem to examine its own
     477                 :            :  * dentries.  It should not be used to look at some other filesystem's
     478                 :            :  * dentries.  (2) It should also be used in combination with d_inode() to get
     479                 :            :  * the inode.
     480                 :            :  */
     481                 :            : static inline bool d_really_is_positive(const struct dentry *dentry)
     482                 :            : {
     483                 :          3 :         return dentry->d_inode != NULL;
     484                 :            : }
     485                 :            : 
     486                 :            : static inline int simple_positive(const struct dentry *dentry)
     487                 :            : {
     488                 :          3 :         return d_really_is_positive(dentry) && !d_unhashed(dentry);
     489                 :            : }
     490                 :            : 
     491                 :            : extern void d_set_fallthru(struct dentry *dentry);
     492                 :            : 
     493                 :            : static inline bool d_is_fallthru(const struct dentry *dentry)
     494                 :            : {
     495                 :            :         return dentry->d_flags & DCACHE_FALLTHRU;
     496                 :            : }
     497                 :            : 
     498                 :            : 
     499                 :            : extern int sysctl_vfs_cache_pressure;
     500                 :            : 
     501                 :            : static inline unsigned long vfs_pressure_ratio(unsigned long val)
     502                 :            : {
     503                 :          0 :         return mult_frac(val, sysctl_vfs_cache_pressure, 100);
     504                 :            : }
     505                 :            : 
     506                 :            : /**
     507                 :            :  * d_inode - Get the actual inode of this dentry
     508                 :            :  * @dentry: The dentry to query
     509                 :            :  *
     510                 :            :  * This is the helper normal filesystems should use to get at their own inodes
     511                 :            :  * in their own dentries and ignore the layering superimposed upon them.
     512                 :            :  */
     513                 :            : static inline struct inode *d_inode(const struct dentry *dentry)
     514                 :            : {
     515                 :          3 :         return dentry->d_inode;
     516                 :            : }
     517                 :            : 
     518                 :            : /**
     519                 :            :  * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE()
     520                 :            :  * @dentry: The dentry to query
     521                 :            :  *
     522                 :            :  * This is the helper normal filesystems should use to get at their own inodes
     523                 :            :  * in their own dentries and ignore the layering superimposed upon them.
     524                 :            :  */
     525                 :            : static inline struct inode *d_inode_rcu(const struct dentry *dentry)
     526                 :            : {
     527                 :          3 :         return READ_ONCE(dentry->d_inode);
     528                 :            : }
     529                 :            : 
     530                 :            : /**
     531                 :            :  * d_backing_inode - Get upper or lower inode we should be using
     532                 :            :  * @upper: The upper layer
     533                 :            :  *
     534                 :            :  * This is the helper that should be used to get at the inode that will be used
     535                 :            :  * if this dentry were to be opened as a file.  The inode may be on the upper
     536                 :            :  * dentry or it may be on a lower dentry pinned by the upper.
     537                 :            :  *
     538                 :            :  * Normal filesystems should not use this to access their own inodes.
     539                 :            :  */
     540                 :            : static inline struct inode *d_backing_inode(const struct dentry *upper)
     541                 :            : {
     542                 :          3 :         struct inode *inode = upper->d_inode;
     543                 :            : 
     544                 :            :         return inode;
     545                 :            : }
     546                 :            : 
     547                 :            : /**
     548                 :            :  * d_backing_dentry - Get upper or lower dentry we should be using
     549                 :            :  * @upper: The upper layer
     550                 :            :  *
     551                 :            :  * This is the helper that should be used to get the dentry of the inode that
     552                 :            :  * will be used if this dentry were opened as a file.  It may be the upper
     553                 :            :  * dentry or it may be a lower dentry pinned by the upper.
     554                 :            :  *
     555                 :            :  * Normal filesystems should not use this to access their own dentries.
     556                 :            :  */
     557                 :            : static inline struct dentry *d_backing_dentry(struct dentry *upper)
     558                 :            : {
     559                 :            :         return upper;
     560                 :            : }
     561                 :            : 
     562                 :            : /**
     563                 :            :  * d_real - Return the real dentry
     564                 :            :  * @dentry: the dentry to query
     565                 :            :  * @inode: inode to select the dentry from multiple layers (can be NULL)
     566                 :            :  *
     567                 :            :  * If dentry is on a union/overlay, then return the underlying, real dentry.
     568                 :            :  * Otherwise return the dentry itself.
     569                 :            :  *
     570                 :            :  * See also: Documentation/filesystems/vfs.rst
     571                 :            :  */
     572                 :            : static inline struct dentry *d_real(struct dentry *dentry,
     573                 :            :                                     const struct inode *inode)
     574                 :            : {
     575                 :          3 :         if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
     576                 :          0 :                 return dentry->d_op->d_real(dentry, inode);
     577                 :            :         else
     578                 :            :                 return dentry;
     579                 :            : }
     580                 :            : 
     581                 :            : /**
     582                 :            :  * d_real_inode - Return the real inode
     583                 :            :  * @dentry: The dentry to query
     584                 :            :  *
     585                 :            :  * If dentry is on a union/overlay, then return the underlying, real inode.
     586                 :            :  * Otherwise return d_inode().
     587                 :            :  */
     588                 :            : static inline struct inode *d_real_inode(const struct dentry *dentry)
     589                 :            : {
     590                 :            :         /* This usage of d_real() results in const dentry */
     591                 :            :         return d_backing_inode(d_real((struct dentry *) dentry, NULL));
     592                 :            : }
     593                 :            : 
     594                 :            : struct name_snapshot {
     595                 :            :         struct qstr name;
     596                 :            :         unsigned char inline_name[DNAME_INLINE_LEN];
     597                 :            : };
     598                 :            : void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
     599                 :            : void release_dentry_name_snapshot(struct name_snapshot *);
     600                 :            : 
     601                 :            : #endif  /* __LINUX_DCACHE_H */