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kernel/include/linux/dcache.h

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/* 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 path;
struct file;
struct vfsmount;
/*
* linux/include/linux/dcache.h
*
* Dirent cache data structures
*
* (C) Copyright 1997 Thomas Schoebel-Theuer,
* with heavy changes by Linus Torvalds
*/
#define IS_ROOT(x) ((x) == (x)->d_parent)
/* The hash is always the low bits of hash_len */
#ifdef __LITTLE_ENDIAN
#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 bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
#endif
/*
* "quick string" -- eases parameter passing, but more importantly
* saves "metadata" about the string (ie length and the hash).
*
* hash comes first so it snuggles against d_parent in the
* dentry.
*/
struct qstr {
union {
struct {
HASH_LEN_DECLARE;
};
u64 hash_len;
};
const unsigned char *name;
};
#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
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
* give reasonable cacheline footprint with larger lines without the
* large memory footprint increase).
*/
#ifdef CONFIG_64BIT
# define DNAME_INLINE_LEN 40 /* 192 bytes */
#else
# ifdef CONFIG_SMP
# define DNAME_INLINE_LEN 36 /* 128 bytes */
# else
# define DNAME_INLINE_LEN 44 /* 128 bytes */
# endif
#endif
#define d_lock d_lockref.lock
struct dentry {
/* RCU lookup touched fields */
unsigned int d_flags; /* protected by d_lock */
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;
struct inode *d_inode; /* Where the name belongs to - NULL is
* negative */
unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
/* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */
/* Ref lookup also touches following */
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!
*/
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_alias and d_rcu can share memory
*/
union {
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;
};
/*
* dentry->d_lock spinlock nesting subclasses:
*
* 0: normal
* 1: nested
*/
enum dentry_d_lock_class
{
DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
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_weak_revalidate)(struct dentry *, unsigned int);
int (*d_hash)(const struct dentry *, struct qstr *);
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)(const struct path *, bool);
struct dentry *(*d_real)(struct dentry *, enum d_real_type type);
} ____cacheline_aligned;
/*
* Locking rules for dentry_operations callbacks are to be found in
* Documentation/filesystems/locking.rst. Keep it updated!
*
* FUrther descriptions are found in Documentation/filesystems/vfs.rst.
* Keep it updated too!
*/
/* d_flags entries */
#define DCACHE_OP_HASH BIT(0)
#define DCACHE_OP_COMPARE BIT(1)
#define DCACHE_OP_REVALIDATE BIT(2)
#define DCACHE_OP_DELETE BIT(3)
#define DCACHE_OP_PRUNE BIT(4)
#define DCACHE_DISCONNECTED BIT(5)
/* 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 BIT(6) /* Recently used, don't discard. */
#define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */
#define DCACHE_CANT_MOUNT BIT(8)
#define DCACHE_GENOCIDE BIT(9)
#define DCACHE_SHRINK_LIST BIT(10)
#define DCACHE_OP_WEAK_REVALIDATE BIT(11)
#define DCACHE_NFSFS_RENAMED BIT(12)
/* this dentry has been "silly renamed" and has to be deleted on the last
* dput() */
#define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(14)
/* Parent inode is watched by some fsnotify listener */
#define DCACHE_DENTRY_KILLED BIT(15)
#define DCACHE_MOUNTED BIT(16) /* is a mountpoint */
#define DCACHE_NEED_AUTOMOUNT BIT(17) /* handle automount on this dir */
#define DCACHE_MANAGE_TRANSIT BIT(18) /* manage transit from this dirent */
#define DCACHE_MANAGED_DENTRY \
(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
#define DCACHE_LRU_LIST BIT(19)
#define DCACHE_ENTRY_TYPE (7 << 20) /* bits 20..22 are for storing type: */
#define DCACHE_MISS_TYPE (0 << 20) /* Negative dentry */
#define DCACHE_WHITEOUT_TYPE (1 << 20) /* Whiteout dentry (stop pathwalk) */
#define DCACHE_DIRECTORY_TYPE (2 << 20) /* Normal directory */
#define DCACHE_AUTODIR_TYPE (3 << 20) /* Lookupless directory (presumed automount) */
#define DCACHE_REGULAR_TYPE (4 << 20) /* Regular file type */
#define DCACHE_SPECIAL_TYPE (5 << 20) /* Other file type */
#define DCACHE_SYMLINK_TYPE (6 << 20) /* Symlink */
#define DCACHE_NOKEY_NAME BIT(25) /* Encrypted name encoded without key */
#define DCACHE_OP_REAL BIT(26)
#define DCACHE_PAR_LOOKUP BIT(28) /* being looked up (with parent locked shared) */
#define DCACHE_DENTRY_CURSOR BIT(29)
#define DCACHE_NORCU BIT(30) /* No RCU delay for freeing */
extern seqlock_t rename_lock;
/*
* These are the low-level FS interfaces to the dcache..
*/
extern void d_instantiate(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_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 *);
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_exact_alias(struct dentry *, struct inode *);
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 d_invalidate(struct dentry *);
/* only used at mount-time */
extern struct dentry * d_make_root(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 struct dentry *d_find_alias_rcu(struct inode *);
/* test whether we have any submounts in a subdir tree */
extern int path_has_submounts(const struct path *);
/*
* This adds the entry to the hash queues.
*/
extern void d_rehash(struct dentry *);
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 *);
extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
static inline unsigned d_count(const struct dentry *dentry)
{
return dentry->d_lockref.count;
}
ino_t d_parent_ino(struct dentry *dentry);
/*
* helper function for dentry_operations.d_dname() members
*/
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(const struct dentry *, char *, int);
extern char *dentry_path(const struct dentry *, char *, int);
/* Allocation counts.. */
/**
* dget_dlock - get a reference to a dentry
* @dentry: dentry to get a reference to
*
* 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)
{
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)
lockref_get(&dentry->d_lockref);
return dentry;
}
extern struct dentry *dget_parent(struct dentry *dentry);
/**
* d_unhashed - is dentry hashed
* @dentry: entry to check
*
* Returns true if the dentry passed is not currently hashed.
*/
static inline int d_unhashed(const struct dentry *dentry)
{
return hlist_bl_unhashed(&dentry->d_hash);
}
static inline int d_unlinked(const struct dentry *dentry)
{
return d_unhashed(dentry) && !IS_ROOT(dentry);
}
static inline int cant_mount(const struct dentry *dentry)
{
return (dentry->d_flags & DCACHE_CANT_MOUNT);
}
static inline void dont_mount(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
dentry->d_flags |= DCACHE_CANT_MOUNT;
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(const struct dentry *dentry)
{
return dentry->d_flags & DCACHE_MANAGED_DENTRY;
}
static inline bool d_mountpoint(const struct dentry *dentry)
{
return dentry->d_flags & DCACHE_MOUNTED;
}
/*
* 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);
}
extern int sysctl_vfs_cache_pressure;
static inline unsigned long vfs_pressure_ratio(unsigned long val)
{
return mult_frac(val, sysctl_vfs_cache_pressure, 100);
}
/**
* 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;
unsigned char inline_name[DNAME_INLINE_LEN];
};
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);
}
#endif /* __LINUX_DCACHE_H */
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