diff options
Diffstat (limited to 'include/linux/dcache.h')
| -rw-r--r-- | include/linux/dcache.h | 594 |
1 files changed, 397 insertions, 197 deletions
diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 3092df3614ae..898c60d21c92 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -1,17 +1,22 @@ +/* SPDX-License-Identifier: GPL-2.0 */ #ifndef __LINUX_DCACHE_H #define __LINUX_DCACHE_H #include <linux/atomic.h> #include <linux/list.h> +#include <linux/math.h> #include <linux/rculist.h> #include <linux/rculist_bl.h> #include <linux/spinlock.h> #include <linux/seqlock.h> #include <linux/cache.h> #include <linux/rcupdate.h> +#include <linux/lockref.h> +#include <linux/stringhash.h> +#include <linux/wait.h> -struct nameidata; struct path; +struct file; struct vfsmount; /* @@ -27,9 +32,11 @@ struct vfsmount; /* The hash is always the low bits of hash_len */ #ifdef __LITTLE_ENDIAN - #define HASH_LEN_DECLARE u32 hash; u32 len; + #define HASH_LEN_DECLARE u32 hash; u32 len + #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8)) #else - #define HASH_LEN_DECLARE u32 len; u32 hash; + #define HASH_LEN_DECLARE u32 len; u32 hash + #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8)) #endif /* @@ -50,40 +57,12 @@ struct qstr { }; #define QSTR_INIT(n,l) { { { .len = l } }, .name = n } -#define hashlen_hash(hashlen) ((u32) (hashlen)) -#define hashlen_len(hashlen) ((u32)((hashlen) >> 32)) - -struct dentry_stat_t { - int nr_dentry; - int nr_unused; - int age_limit; /* age in seconds */ - int want_pages; /* pages requested by system */ - int dummy[2]; -}; -extern struct dentry_stat_t dentry_stat; - -/* Name hashing routines. Initial hash value */ -/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */ -#define init_name_hash() 0 +#define QSTR_LEN(n,l) (struct qstr)QSTR_INIT(n,l) +#define QSTR(n) QSTR_LEN(n, strlen(n)) -/* partial hash update function. Assume roughly 4 bits per character */ -static inline unsigned long -partial_name_hash(unsigned long c, unsigned long prevhash) -{ - return (prevhash + (c << 4) + (c >> 4)) * 11; -} - -/* - * Finally: cut down the number of bits to a int value (and try to avoid - * losing bits) - */ -static inline unsigned long end_name_hash(unsigned long hash) -{ - return (unsigned int) hash; -} - -/* Compute the hash for a name string. */ -extern unsigned int full_name_hash(const unsigned char *, unsigned int); +extern const struct qstr empty_name; +extern const struct qstr slash_name; +extern const struct qstr dotdot_name; /* * Try to keep struct dentry aligned on 64 byte cachelines (this will @@ -91,44 +70,65 @@ extern unsigned int full_name_hash(const unsigned char *, unsigned int); * large memory footprint increase). */ #ifdef CONFIG_64BIT -# define DNAME_INLINE_LEN 32 /* 192 bytes */ +# define DNAME_INLINE_WORDS 5 /* 192 bytes */ #else # ifdef CONFIG_SMP -# define DNAME_INLINE_LEN 36 /* 128 bytes */ +# define DNAME_INLINE_WORDS 9 /* 128 bytes */ # else -# define DNAME_INLINE_LEN 40 /* 128 bytes */ +# define DNAME_INLINE_WORDS 11 /* 128 bytes */ # endif #endif +#define DNAME_INLINE_LEN (DNAME_INLINE_WORDS*sizeof(unsigned long)) + +union shortname_store { + unsigned char string[DNAME_INLINE_LEN]; + unsigned long words[DNAME_INLINE_WORDS]; +}; + +#define d_lock d_lockref.lock +#define d_iname d_shortname.string + struct dentry { /* RCU lookup touched fields */ unsigned int d_flags; /* protected by d_lock */ - seqcount_t d_seq; /* per dentry seqlock */ + seqcount_spinlock_t d_seq; /* per dentry seqlock */ struct hlist_bl_node d_hash; /* lookup hash list */ struct dentry *d_parent; /* parent directory */ - struct qstr d_name; + union { + struct qstr __d_name; /* for use ONLY in fs/dcache.c */ + const struct qstr d_name; + }; struct inode *d_inode; /* Where the name belongs to - NULL is * negative */ - unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ + union shortname_store d_shortname; + /* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */ /* Ref lookup also touches following */ - unsigned int d_count; /* protected by d_lock */ - spinlock_t d_lock; /* per dentry lock */ const struct dentry_operations *d_op; struct super_block *d_sb; /* The root of the dentry tree */ unsigned long d_time; /* used by d_revalidate */ void *d_fsdata; /* fs-specific data */ + /* --- cacheline 2 boundary (128 bytes) --- */ + struct lockref d_lockref; /* per-dentry lock and refcount + * keep separate from RCU lookup area if + * possible! + */ - struct list_head d_lru; /* LRU list */ + union { + struct list_head d_lru; /* LRU list */ + wait_queue_head_t *d_wait; /* in-lookup ones only */ + }; + struct hlist_node d_sib; /* child of parent list */ + struct hlist_head d_children; /* our children */ /* - * d_child and d_rcu can share memory + * d_alias and d_rcu can share memory */ union { - struct list_head d_child; /* child of parent list */ + struct hlist_node d_alias; /* inode alias list */ + struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ struct rcu_head d_rcu; } d_u; - struct list_head d_subdirs; /* our children */ - struct hlist_node d_alias; /* inode alias list */ }; /* @@ -143,253 +143,235 @@ enum dentry_d_lock_class DENTRY_D_LOCK_NESTED }; +enum d_real_type { + D_REAL_DATA, + D_REAL_METADATA, +}; + struct dentry_operations { - int (*d_revalidate)(struct dentry *, unsigned int); + int (*d_revalidate)(struct inode *, const struct qstr *, + struct dentry *, unsigned int); int (*d_weak_revalidate)(struct dentry *, unsigned int); int (*d_hash)(const struct dentry *, struct qstr *); - int (*d_compare)(const struct dentry *, const struct dentry *, + int (*d_compare)(const struct dentry *, unsigned int, const char *, const struct qstr *); int (*d_delete)(const struct dentry *); + int (*d_init)(struct dentry *); void (*d_release)(struct dentry *); void (*d_prune)(struct dentry *); void (*d_iput)(struct dentry *, struct inode *); char *(*d_dname)(struct dentry *, char *, int); struct vfsmount *(*d_automount)(struct path *); - int (*d_manage)(struct dentry *, bool); + int (*d_manage)(const struct path *, bool); + struct dentry *(*d_real)(struct dentry *, enum d_real_type type); + bool (*d_unalias_trylock)(const struct dentry *); + void (*d_unalias_unlock)(const struct dentry *); } ____cacheline_aligned; /* * Locking rules for dentry_operations callbacks are to be found in - * Documentation/filesystems/Locking. Keep it updated! + * Documentation/filesystems/locking.rst. Keep it updated! * - * FUrther descriptions are found in Documentation/filesystems/vfs.txt. + * FUrther descriptions are found in Documentation/filesystems/vfs.rst. * Keep it updated too! */ /* d_flags entries */ -#define DCACHE_OP_HASH 0x0001 -#define DCACHE_OP_COMPARE 0x0002 -#define DCACHE_OP_REVALIDATE 0x0004 -#define DCACHE_OP_DELETE 0x0008 -#define DCACHE_OP_PRUNE 0x0010 - -#define DCACHE_DISCONNECTED 0x0020 - /* This dentry is possibly not currently connected to the dcache tree, in - * which case its parent will either be itself, or will have this flag as - * well. nfsd will not use a dentry with this bit set, but will first - * endeavour to clear the bit either by discovering that it is connected, - * or by performing lookup operations. Any filesystem which supports - * nfsd_operations MUST have a lookup function which, if it finds a - * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that - * dentry into place and return that dentry rather than the passed one, - * typically using d_splice_alias. */ - -#define DCACHE_REFERENCED 0x0040 /* Recently used, don't discard. */ -#define DCACHE_RCUACCESS 0x0080 /* Entry has ever been RCU-visible */ - -#define DCACHE_CANT_MOUNT 0x0100 -#define DCACHE_GENOCIDE 0x0200 -#define DCACHE_SHRINK_LIST 0x0400 - -#define DCACHE_OP_WEAK_REVALIDATE 0x0800 - -#define DCACHE_NFSFS_RENAMED 0x1000 - /* this dentry has been "silly renamed" and has to be deleted on the last - * dput() */ -#define DCACHE_COOKIE 0x2000 /* For use by dcookie subsystem */ -#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x4000 - /* Parent inode is watched by some fsnotify listener */ - -#define DCACHE_MOUNTED 0x10000 /* is a mountpoint */ -#define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */ -#define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */ +enum dentry_flags { + DCACHE_OP_HASH = BIT(0), + DCACHE_OP_COMPARE = BIT(1), + DCACHE_OP_REVALIDATE = BIT(2), + DCACHE_OP_DELETE = BIT(3), + DCACHE_OP_PRUNE = BIT(4), + /* + * This dentry is possibly not currently connected to the dcache tree, + * in which case its parent will either be itself, or will have this + * flag as well. nfsd will not use a dentry with this bit set, but will + * first endeavour to clear the bit either by discovering that it is + * connected, or by performing lookup operations. Any filesystem which + * supports nfsd_operations MUST have a lookup function which, if it + * finds a directory inode with a DCACHE_DISCONNECTED dentry, will + * d_move that dentry into place and return that dentry rather than the + * passed one, typically using d_splice_alias. + */ + DCACHE_DISCONNECTED = BIT(5), + DCACHE_REFERENCED = BIT(6), /* Recently used, don't discard. */ + DCACHE_DONTCACHE = BIT(7), /* Purge from memory on final dput() */ + DCACHE_CANT_MOUNT = BIT(8), + DCACHE_SHRINK_LIST = BIT(10), + DCACHE_OP_WEAK_REVALIDATE = BIT(11), + /* + * this dentry has been "silly renamed" and has to be deleted on the + * last dput() + */ + DCACHE_NFSFS_RENAMED = BIT(12), + DCACHE_FSNOTIFY_PARENT_WATCHED = BIT(13), /* Parent inode is watched by some fsnotify listener */ + DCACHE_DENTRY_KILLED = BIT(14), + DCACHE_MOUNTED = BIT(15), /* is a mountpoint */ + DCACHE_NEED_AUTOMOUNT = BIT(16), /* handle automount on this dir */ + DCACHE_MANAGE_TRANSIT = BIT(17), /* manage transit from this dirent */ + DCACHE_LRU_LIST = BIT(18), + DCACHE_ENTRY_TYPE = (7 << 19), /* bits 19..21 are for storing type: */ + DCACHE_MISS_TYPE = (0 << 19), /* Negative dentry */ + DCACHE_WHITEOUT_TYPE = (1 << 19), /* Whiteout dentry (stop pathwalk) */ + DCACHE_DIRECTORY_TYPE = (2 << 19), /* Normal directory */ + DCACHE_AUTODIR_TYPE = (3 << 19), /* Lookupless directory (presumed automount) */ + DCACHE_REGULAR_TYPE = (4 << 19), /* Regular file type */ + DCACHE_SPECIAL_TYPE = (5 << 19), /* Other file type */ + DCACHE_SYMLINK_TYPE = (6 << 19), /* Symlink */ + DCACHE_NOKEY_NAME = BIT(22), /* Encrypted name encoded without key */ + DCACHE_OP_REAL = BIT(23), + DCACHE_PAR_LOOKUP = BIT(24), /* being looked up (with parent locked shared) */ + DCACHE_DENTRY_CURSOR = BIT(25), + DCACHE_NORCU = BIT(26), /* No RCU delay for freeing */ + DCACHE_PERSISTENT = BIT(27) +}; + #define DCACHE_MANAGED_DENTRY \ (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT) -#define DCACHE_DENTRY_KILLED 0x100000 - extern seqlock_t rename_lock; -static inline int dname_external(struct dentry *dentry) -{ - return dentry->d_name.name != dentry->d_iname; -} - /* * These are the low-level FS interfaces to the dcache.. */ extern void d_instantiate(struct dentry *, struct inode *); -extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *); -extern struct dentry * d_materialise_unique(struct dentry *, struct inode *); +extern void d_instantiate_new(struct dentry *, struct inode *); extern void __d_drop(struct dentry *dentry); extern void d_drop(struct dentry *dentry); extern void d_delete(struct dentry *); -extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op); /* allocate/de-allocate */ extern struct dentry * d_alloc(struct dentry *, const struct qstr *); -extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); +extern struct dentry * d_alloc_anon(struct super_block *); +extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, + wait_queue_head_t *); extern struct dentry * d_splice_alias(struct inode *, struct dentry *); +/* weird procfs mess; *NOT* exported */ +extern struct dentry * d_splice_alias_ops(struct inode *, struct dentry *, + const struct dentry_operations *); extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); +extern bool d_same_name(const struct dentry *dentry, const struct dentry *parent, + const struct qstr *name); extern struct dentry *d_find_any_alias(struct inode *inode); extern struct dentry * d_obtain_alias(struct inode *); +extern struct dentry * d_obtain_root(struct inode *); extern void shrink_dcache_sb(struct super_block *); extern void shrink_dcache_parent(struct dentry *); -extern void shrink_dcache_for_umount(struct super_block *); -extern int d_invalidate(struct dentry *); +extern void d_invalidate(struct dentry *); /* only used at mount-time */ extern struct dentry * d_make_root(struct inode *); -/* <clickety>-<click> the ramfs-type tree */ -extern void d_genocide(struct dentry *); - -extern void d_tmpfile(struct dentry *, struct inode *); +extern void d_mark_tmpfile(struct file *, struct inode *); +extern void d_tmpfile(struct file *, struct inode *); extern struct dentry *d_find_alias(struct inode *); extern void d_prune_aliases(struct inode *); +extern void d_dispose_if_unused(struct dentry *, struct list_head *); +extern void shrink_dentry_list(struct list_head *); + +extern struct dentry *d_find_alias_rcu(struct inode *); /* test whether we have any submounts in a subdir tree */ -extern int have_submounts(struct dentry *); +extern int path_has_submounts(const struct path *); /* * This adds the entry to the hash queues. */ extern void d_rehash(struct dentry *); - -/** - * d_add - add dentry to hash queues - * @entry: dentry to add - * @inode: The inode to attach to this dentry - * - * This adds the entry to the hash queues and initializes @inode. - * The entry was actually filled in earlier during d_alloc(). - */ -static inline void d_add(struct dentry *entry, struct inode *inode) -{ - d_instantiate(entry, inode); - d_rehash(entry); -} - -/** - * d_add_unique - add dentry to hash queues without aliasing - * @entry: dentry to add - * @inode: The inode to attach to this dentry - * - * This adds the entry to the hash queues and initializes @inode. - * The entry was actually filled in earlier during d_alloc(). - */ -static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode) -{ - struct dentry *res; - - res = d_instantiate_unique(entry, inode); - d_rehash(res != NULL ? res : entry); - return res; -} - -extern void dentry_update_name_case(struct dentry *, struct qstr *); +extern void d_add(struct dentry *, struct inode *); /* used for rename() and baskets */ extern void d_move(struct dentry *, struct dentry *); +extern void d_exchange(struct dentry *, struct dentry *); extern struct dentry *d_ancestor(struct dentry *, struct dentry *); -/* appendix may either be NULL or be used for transname suffixes */ extern struct dentry *d_lookup(const struct dentry *, const struct qstr *); -extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *); -extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *); -extern struct dentry *__d_lookup_rcu(const struct dentry *parent, - const struct qstr *name, unsigned *seq); - -/** - * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok - * @dentry: dentry to take a ref on - * @seq: seqcount to verify against - * Returns: 0 on failure, else 1. - * - * __d_rcu_to_refcount operates on a dentry,seq pair that was returned - * by __d_lookup_rcu, to get a reference on an rcu-walk dentry. - */ -static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq) -{ - int ret = 0; - - assert_spin_locked(&dentry->d_lock); - if (!read_seqcount_retry(&dentry->d_seq, seq)) { - ret = 1; - dentry->d_count++; - } - - return ret; -} -static inline unsigned d_count(struct dentry *dentry) +static inline unsigned d_count(const struct dentry *dentry) { - return dentry->d_count; + return dentry->d_lockref.count; } -/* validate "insecure" dentry pointer */ -extern int d_validate(struct dentry *, struct dentry *); +ino_t d_parent_ino(struct dentry *dentry); /* * helper function for dentry_operations.d_dname() members */ -extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); +extern __printf(3, 4) +char *dynamic_dname(char *, int, const char *, ...); extern char *__d_path(const struct path *, const struct path *, char *, int); extern char *d_absolute_path(const struct path *, char *, int); extern char *d_path(const struct path *, char *, int); -extern char *dentry_path_raw(struct dentry *, char *, int); -extern char *dentry_path(struct dentry *, char *, int); +extern char *dentry_path_raw(const struct dentry *, char *, int); +extern char *dentry_path(const struct dentry *, char *, int); /* Allocation counts.. */ /** - * dget, dget_dlock - get a reference to a dentry - * @dentry: dentry to get a reference to + * dget_dlock - get a reference to a dentry + * @dentry: dentry to get a reference to * - * Given a dentry or %NULL pointer increment the reference count - * if appropriate and return the dentry. A dentry will not be - * destroyed when it has references. + * Given a live dentry, increment the reference count and return the dentry. + * Caller must hold @dentry->d_lock. Making sure that dentry is alive is + * caller's resonsibility. There are many conditions sufficient to guarantee + * that; e.g. anything with non-negative refcount is alive, so's anything + * hashed, anything positive, anyone's parent, etc. */ static inline struct dentry *dget_dlock(struct dentry *dentry) { - if (dentry) - dentry->d_count++; + dentry->d_lockref.count++; return dentry; } + +/** + * dget - get a reference to a dentry + * @dentry: dentry to get a reference to + * + * Given a dentry or %NULL pointer increment the reference count + * if appropriate and return the dentry. A dentry will not be + * destroyed when it has references. Conversely, a dentry with + * no references can disappear for any number of reasons, starting + * with memory pressure. In other words, that primitive is + * used to clone an existing reference; using it on something with + * zero refcount is a bug. + * + * NOTE: it will spin if @dentry->d_lock is held. From the deadlock + * avoidance point of view it is equivalent to spin_lock()/increment + * refcount/spin_unlock(), so calling it under @dentry->d_lock is + * always a bug; so's calling it under ->d_lock on any of its descendents. + * + */ static inline struct dentry *dget(struct dentry *dentry) { - if (dentry) { - spin_lock(&dentry->d_lock); - dget_dlock(dentry); - spin_unlock(&dentry->d_lock); - } + if (dentry) + lockref_get(&dentry->d_lockref); return dentry; } extern struct dentry *dget_parent(struct dentry *dentry); /** - * d_unhashed - is dentry hashed - * @dentry: entry to check + * d_unhashed - is dentry hashed + * @dentry: entry to check * - * Returns true if the dentry passed is not currently hashed. + * Returns true if the dentry passed is not currently hashed. */ - -static inline int d_unhashed(struct dentry *dentry) +static inline int d_unhashed(const struct dentry *dentry) { return hlist_bl_unhashed(&dentry->d_hash); } -static inline int d_unlinked(struct dentry *dentry) +static inline int d_unlinked(const struct dentry *dentry) { return d_unhashed(dentry) && !IS_ROOT(dentry); } -static inline int cant_mount(struct dentry *dentry) +static inline int cant_mount(const struct dentry *dentry) { return (dentry->d_flags & DCACHE_CANT_MOUNT); } @@ -401,18 +383,236 @@ static inline void dont_mount(struct dentry *dentry) spin_unlock(&dentry->d_lock); } +extern void __d_lookup_unhash_wake(struct dentry *dentry); + +static inline int d_in_lookup(const struct dentry *dentry) +{ + return dentry->d_flags & DCACHE_PAR_LOOKUP; +} + +static inline void d_lookup_done(struct dentry *dentry) +{ + if (unlikely(d_in_lookup(dentry))) + __d_lookup_unhash_wake(dentry); +} + extern void dput(struct dentry *); -static inline bool d_managed(struct dentry *dentry) +static inline bool d_managed(const struct dentry *dentry) { return dentry->d_flags & DCACHE_MANAGED_DENTRY; } -static inline bool d_mountpoint(struct dentry *dentry) +static inline bool d_mountpoint(const struct dentry *dentry) { return dentry->d_flags & DCACHE_MOUNTED; } -extern int sysctl_vfs_cache_pressure; +/* + * Directory cache entry type accessor functions. + */ +static inline unsigned __d_entry_type(const struct dentry *dentry) +{ + return dentry->d_flags & DCACHE_ENTRY_TYPE; +} + +static inline bool d_is_miss(const struct dentry *dentry) +{ + return __d_entry_type(dentry) == DCACHE_MISS_TYPE; +} + +static inline bool d_is_whiteout(const struct dentry *dentry) +{ + return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE; +} + +static inline bool d_can_lookup(const struct dentry *dentry) +{ + return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE; +} + +static inline bool d_is_autodir(const struct dentry *dentry) +{ + return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE; +} + +static inline bool d_is_dir(const struct dentry *dentry) +{ + return d_can_lookup(dentry) || d_is_autodir(dentry); +} + +static inline bool d_is_symlink(const struct dentry *dentry) +{ + return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE; +} + +static inline bool d_is_reg(const struct dentry *dentry) +{ + return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE; +} + +static inline bool d_is_special(const struct dentry *dentry) +{ + return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE; +} + +static inline bool d_is_file(const struct dentry *dentry) +{ + return d_is_reg(dentry) || d_is_special(dentry); +} + +static inline bool d_is_negative(const struct dentry *dentry) +{ + // TODO: check d_is_whiteout(dentry) also. + return d_is_miss(dentry); +} + +static inline bool d_flags_negative(unsigned flags) +{ + return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE; +} + +static inline bool d_is_positive(const struct dentry *dentry) +{ + return !d_is_negative(dentry); +} + +/** + * d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs) + * @dentry: The dentry in question + * + * Returns true if the dentry represents either an absent name or a name that + * doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent + * a true miss, a whiteout that isn't represented by a 0,0 chardev or a + * fallthrough marker in an opaque directory. + * + * Note! (1) This should be used *only* by a filesystem to examine its own + * dentries. It should not be used to look at some other filesystem's + * dentries. (2) It should also be used in combination with d_inode() to get + * the inode. (3) The dentry may have something attached to ->d_lower and the + * type field of the flags may be set to something other than miss or whiteout. + */ +static inline bool d_really_is_negative(const struct dentry *dentry) +{ + return dentry->d_inode == NULL; +} + +/** + * d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs) + * @dentry: The dentry in question + * + * Returns true if the dentry represents a name that maps to an inode + * (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if + * that is represented on medium as a 0,0 chardev. + * + * Note! (1) This should be used *only* by a filesystem to examine its own + * dentries. It should not be used to look at some other filesystem's + * dentries. (2) It should also be used in combination with d_inode() to get + * the inode. + */ +static inline bool d_really_is_positive(const struct dentry *dentry) +{ + return dentry->d_inode != NULL; +} + +static inline int simple_positive(const struct dentry *dentry) +{ + return d_really_is_positive(dentry) && !d_unhashed(dentry); +} + +unsigned long vfs_pressure_ratio(unsigned long val); + +/** + * d_inode - Get the actual inode of this dentry + * @dentry: The dentry to query + * + * This is the helper normal filesystems should use to get at their own inodes + * in their own dentries and ignore the layering superimposed upon them. + */ +static inline struct inode *d_inode(const struct dentry *dentry) +{ + return dentry->d_inode; +} + +/** + * d_inode_rcu - Get the actual inode of this dentry with READ_ONCE() + * @dentry: The dentry to query + * + * This is the helper normal filesystems should use to get at their own inodes + * in their own dentries and ignore the layering superimposed upon them. + */ +static inline struct inode *d_inode_rcu(const struct dentry *dentry) +{ + return READ_ONCE(dentry->d_inode); +} + +/** + * d_backing_inode - Get upper or lower inode we should be using + * @upper: The upper layer + * + * This is the helper that should be used to get at the inode that will be used + * if this dentry were to be opened as a file. The inode may be on the upper + * dentry or it may be on a lower dentry pinned by the upper. + * + * Normal filesystems should not use this to access their own inodes. + */ +static inline struct inode *d_backing_inode(const struct dentry *upper) +{ + struct inode *inode = upper->d_inode; + + return inode; +} + +/** + * d_real - Return the real dentry + * @dentry: the dentry to query + * @type: the type of real dentry (data or metadata) + * + * If dentry is on a union/overlay, then return the underlying, real dentry. + * Otherwise return the dentry itself. + * + * See also: Documentation/filesystems/vfs.rst + */ +static inline struct dentry *d_real(struct dentry *dentry, enum d_real_type type) +{ + if (unlikely(dentry->d_flags & DCACHE_OP_REAL)) + return dentry->d_op->d_real(dentry, type); + else + return dentry; +} + +/** + * d_real_inode - Return the real inode hosting the data + * @dentry: The dentry to query + * + * If dentry is on a union/overlay, then return the underlying, real inode. + * Otherwise return d_inode(). + */ +static inline struct inode *d_real_inode(const struct dentry *dentry) +{ + /* This usage of d_real() results in const dentry */ + return d_inode(d_real((struct dentry *) dentry, D_REAL_DATA)); +} + +struct name_snapshot { + struct qstr name; + union shortname_store inline_name; +}; +void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *); +void release_dentry_name_snapshot(struct name_snapshot *); + +static inline struct dentry *d_first_child(const struct dentry *dentry) +{ + return hlist_entry_safe(dentry->d_children.first, struct dentry, d_sib); +} + +static inline struct dentry *d_next_sibling(const struct dentry *dentry) +{ + return hlist_entry_safe(dentry->d_sib.next, struct dentry, d_sib); +} + +void set_default_d_op(struct super_block *, const struct dentry_operations *); +struct dentry *d_make_persistent(struct dentry *, struct inode *); +void d_make_discardable(struct dentry *dentry); #endif /* __LINUX_DCACHE_H */ |