607 lines
18 KiB
C
607 lines
18 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_DCACHE_H
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#define __LINUX_DCACHE_H
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#include <linux/atomic.h>
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#include <linux/list.h>
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#include <linux/rculist.h>
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#include <linux/rculist_bl.h>
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#include <linux/spinlock.h>
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#include <linux/seqlock.h>
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#include <linux/cache.h>
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#include <linux/rcupdate.h>
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#include <linux/lockref.h>
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#include <linux/stringhash.h>
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#include <linux/wait.h>
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struct path;
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struct vfsmount;
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/*
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* linux/include/linux/dcache.h
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*
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* Dirent cache data structures
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*
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* (C) Copyright 1997 Thomas Schoebel-Theuer,
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* with heavy changes by Linus Torvalds
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*/
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#define IS_ROOT(x) ((x) == (x)->d_parent)
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/* The hash is always the low bits of hash_len */
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#ifdef __LITTLE_ENDIAN
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#define HASH_LEN_DECLARE u32 hash; u32 len
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#define bytemask_from_count(cnt) (~(~0ul << (cnt)*8))
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#else
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#define HASH_LEN_DECLARE u32 len; u32 hash
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#define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8))
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#endif
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/*
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* "quick string" -- eases parameter passing, but more importantly
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* saves "metadata" about the string (ie length and the hash).
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*
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* hash comes first so it snuggles against d_parent in the
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* dentry.
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*/
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struct qstr {
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union {
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struct {
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HASH_LEN_DECLARE;
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};
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u64 hash_len;
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};
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const unsigned char *name;
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};
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#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
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extern const struct qstr empty_name;
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extern const struct qstr slash_name;
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struct dentry_stat_t {
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long nr_dentry;
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long nr_unused;
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long age_limit; /* age in seconds */
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long want_pages; /* pages requested by system */
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long nr_negative; /* # of unused negative dentries */
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long dummy; /* Reserved for future use */
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};
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extern struct dentry_stat_t dentry_stat;
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/*
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* Try to keep struct dentry aligned on 64 byte cachelines (this will
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* give reasonable cacheline footprint with larger lines without the
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* large memory footprint increase).
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*/
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#ifdef CONFIG_64BIT
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# define DNAME_INLINE_LEN 32 /* 192 bytes */
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#else
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# ifdef CONFIG_SMP
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# define DNAME_INLINE_LEN 36 /* 128 bytes */
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# else
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# define DNAME_INLINE_LEN 40 /* 128 bytes */
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# endif
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#endif
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#define d_lock d_lockref.lock
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struct dentry {
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/* RCU lookup touched fields */
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unsigned int d_flags; /* protected by d_lock */
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seqcount_t d_seq; /* per dentry seqlock */
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struct hlist_bl_node d_hash; /* lookup hash list */
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struct dentry *d_parent; /* parent directory */
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struct qstr d_name;
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struct inode *d_inode; /* Where the name belongs to - NULL is
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* negative */
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unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
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/* Ref lookup also touches following */
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struct lockref d_lockref; /* per-dentry lock and refcount */
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const struct dentry_operations *d_op;
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struct super_block *d_sb; /* The root of the dentry tree */
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unsigned long d_time; /* used by d_revalidate */
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void *d_fsdata; /* fs-specific data */
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union {
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struct list_head d_lru; /* LRU list */
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wait_queue_head_t *d_wait; /* in-lookup ones only */
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};
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struct list_head d_child; /* child of parent list */
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struct list_head d_subdirs; /* our children */
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/*
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* d_alias and d_rcu can share memory
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*/
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union {
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struct hlist_node d_alias; /* inode alias list */
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struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */
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struct rcu_head d_rcu;
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} d_u;
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} __randomize_layout;
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/*
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* dentry->d_lock spinlock nesting subclasses:
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*
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* 0: normal
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* 1: nested
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*/
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enum dentry_d_lock_class
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{
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DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
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DENTRY_D_LOCK_NESTED
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};
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struct dentry_operations {
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int (*d_revalidate)(struct dentry *, unsigned int);
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int (*d_weak_revalidate)(struct dentry *, unsigned int);
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int (*d_hash)(const struct dentry *, struct qstr *);
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int (*d_compare)(const struct dentry *,
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unsigned int, const char *, const struct qstr *);
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int (*d_delete)(const struct dentry *);
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int (*d_init)(struct dentry *);
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void (*d_release)(struct dentry *);
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void (*d_prune)(struct dentry *);
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void (*d_iput)(struct dentry *, struct inode *);
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char *(*d_dname)(struct dentry *, char *, int);
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struct vfsmount *(*d_automount)(struct path *);
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int (*d_manage)(const struct path *, bool);
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struct dentry *(*d_real)(struct dentry *, const struct inode *);
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} ____cacheline_aligned;
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/*
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* Locking rules for dentry_operations callbacks are to be found in
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* Documentation/filesystems/locking.rst. Keep it updated!
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*
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* FUrther descriptions are found in Documentation/filesystems/vfs.rst.
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* Keep it updated too!
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*/
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/* d_flags entries */
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#define DCACHE_OP_HASH 0x00000001
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#define DCACHE_OP_COMPARE 0x00000002
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#define DCACHE_OP_REVALIDATE 0x00000004
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#define DCACHE_OP_DELETE 0x00000008
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#define DCACHE_OP_PRUNE 0x00000010
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#define DCACHE_DISCONNECTED 0x00000020
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/* This dentry is possibly not currently connected to the dcache tree, in
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* which case its parent will either be itself, or will have this flag as
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* well. nfsd will not use a dentry with this bit set, but will first
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* endeavour to clear the bit either by discovering that it is connected,
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* or by performing lookup operations. Any filesystem which supports
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* nfsd_operations MUST have a lookup function which, if it finds a
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* directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
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* dentry into place and return that dentry rather than the passed one,
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* typically using d_splice_alias. */
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#define DCACHE_REFERENCED 0x00000040 /* Recently used, don't discard. */
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#define DCACHE_CANT_MOUNT 0x00000100
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#define DCACHE_GENOCIDE 0x00000200
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#define DCACHE_SHRINK_LIST 0x00000400
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#define DCACHE_OP_WEAK_REVALIDATE 0x00000800
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#define DCACHE_NFSFS_RENAMED 0x00001000
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/* this dentry has been "silly renamed" and has to be deleted on the last
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* dput() */
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#define DCACHE_COOKIE 0x00002000 /* For use by dcookie subsystem */
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#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x00004000
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/* Parent inode is watched by some fsnotify listener */
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#define DCACHE_DENTRY_KILLED 0x00008000
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#define DCACHE_MOUNTED 0x00010000 /* is a mountpoint */
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#define DCACHE_NEED_AUTOMOUNT 0x00020000 /* handle automount on this dir */
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#define DCACHE_MANAGE_TRANSIT 0x00040000 /* manage transit from this dirent */
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#define DCACHE_MANAGED_DENTRY \
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(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
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#define DCACHE_LRU_LIST 0x00080000
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#define DCACHE_ENTRY_TYPE 0x00700000
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#define DCACHE_MISS_TYPE 0x00000000 /* Negative dentry (maybe fallthru to nowhere) */
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#define DCACHE_WHITEOUT_TYPE 0x00100000 /* Whiteout dentry (stop pathwalk) */
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#define DCACHE_DIRECTORY_TYPE 0x00200000 /* Normal directory */
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#define DCACHE_AUTODIR_TYPE 0x00300000 /* Lookupless directory (presumed automount) */
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#define DCACHE_REGULAR_TYPE 0x00400000 /* Regular file type (or fallthru to such) */
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#define DCACHE_SPECIAL_TYPE 0x00500000 /* Other file type (or fallthru to such) */
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#define DCACHE_SYMLINK_TYPE 0x00600000 /* Symlink (or fallthru to such) */
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#define DCACHE_MAY_FREE 0x00800000
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#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
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#define DCACHE_ENCRYPTED_NAME 0x02000000 /* Encrypted name (dir key was unavailable) */
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#define DCACHE_OP_REAL 0x04000000
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#define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
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#define DCACHE_DENTRY_CURSOR 0x20000000
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#define DCACHE_NORCU 0x40000000 /* No RCU delay for freeing */
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extern seqlock_t rename_lock;
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/*
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* These are the low-level FS interfaces to the dcache..
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*/
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extern void d_instantiate(struct dentry *, struct inode *);
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extern void d_instantiate_new(struct dentry *, struct inode *);
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extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
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extern struct dentry * d_instantiate_anon(struct dentry *, struct inode *);
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extern void __d_drop(struct dentry *dentry);
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extern void d_drop(struct dentry *dentry);
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extern void d_delete(struct dentry *);
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extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);
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/* allocate/de-allocate */
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extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
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extern struct dentry * d_alloc_anon(struct super_block *);
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extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
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wait_queue_head_t *);
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extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
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extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
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extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
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extern struct dentry *d_find_any_alias(struct inode *inode);
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extern struct dentry * d_obtain_alias(struct inode *);
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extern struct dentry * d_obtain_root(struct inode *);
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extern void shrink_dcache_sb(struct super_block *);
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extern void shrink_dcache_parent(struct dentry *);
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extern void shrink_dcache_for_umount(struct super_block *);
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extern void d_invalidate(struct dentry *);
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/* only used at mount-time */
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extern struct dentry * d_make_root(struct inode *);
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/* <clickety>-<click> the ramfs-type tree */
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extern void d_genocide(struct dentry *);
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extern void d_tmpfile(struct dentry *, struct inode *);
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extern struct dentry *d_find_alias(struct inode *);
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extern void d_prune_aliases(struct inode *);
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/* test whether we have any submounts in a subdir tree */
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extern int path_has_submounts(const struct path *);
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/*
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* This adds the entry to the hash queues.
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*/
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extern void d_rehash(struct dentry *);
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extern void d_add(struct dentry *, struct inode *);
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/* used for rename() and baskets */
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extern void d_move(struct dentry *, struct dentry *);
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extern void d_exchange(struct dentry *, struct dentry *);
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extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
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/* appendix may either be NULL or be used for transname suffixes */
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extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
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extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
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extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
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extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
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const struct qstr *name, unsigned *seq);
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static inline unsigned d_count(const struct dentry *dentry)
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{
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return dentry->d_lockref.count;
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}
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/*
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* helper function for dentry_operations.d_dname() members
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*/
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extern __printf(4, 5)
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char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
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extern char *__d_path(const struct path *, const struct path *, char *, int);
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extern char *d_absolute_path(const struct path *, char *, int);
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extern char *d_path(const struct path *, char *, int);
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extern char *dentry_path_raw(struct dentry *, char *, int);
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extern char *dentry_path(struct dentry *, char *, int);
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/* Allocation counts.. */
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/**
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* dget, dget_dlock - get a reference to a dentry
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* @dentry: dentry to get a reference to
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*
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* Given a dentry or %NULL pointer increment the reference count
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* if appropriate and return the dentry. A dentry will not be
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* destroyed when it has references.
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*/
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static inline struct dentry *dget_dlock(struct dentry *dentry)
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{
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if (dentry)
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dentry->d_lockref.count++;
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return dentry;
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}
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static inline struct dentry *dget(struct dentry *dentry)
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{
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if (dentry)
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lockref_get(&dentry->d_lockref);
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return dentry;
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}
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extern struct dentry *dget_parent(struct dentry *dentry);
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/**
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* d_unhashed - is dentry hashed
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* @dentry: entry to check
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*
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* Returns true if the dentry passed is not currently hashed.
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*/
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static inline int d_unhashed(const struct dentry *dentry)
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{
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return hlist_bl_unhashed(&dentry->d_hash);
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}
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static inline int d_unlinked(const struct dentry *dentry)
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{
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return d_unhashed(dentry) && !IS_ROOT(dentry);
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}
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static inline int cant_mount(const struct dentry *dentry)
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{
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return (dentry->d_flags & DCACHE_CANT_MOUNT);
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}
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static inline void dont_mount(struct dentry *dentry)
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{
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spin_lock(&dentry->d_lock);
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dentry->d_flags |= DCACHE_CANT_MOUNT;
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spin_unlock(&dentry->d_lock);
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}
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extern void __d_lookup_done(struct dentry *);
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static inline int d_in_lookup(const struct dentry *dentry)
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{
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return dentry->d_flags & DCACHE_PAR_LOOKUP;
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}
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static inline void d_lookup_done(struct dentry *dentry)
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{
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if (unlikely(d_in_lookup(dentry))) {
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spin_lock(&dentry->d_lock);
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__d_lookup_done(dentry);
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spin_unlock(&dentry->d_lock);
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}
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}
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extern void dput(struct dentry *);
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static inline bool d_managed(const struct dentry *dentry)
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{
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return dentry->d_flags & DCACHE_MANAGED_DENTRY;
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}
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static inline bool d_mountpoint(const struct dentry *dentry)
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{
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return dentry->d_flags & DCACHE_MOUNTED;
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}
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/*
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* Directory cache entry type accessor functions.
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*/
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static inline unsigned __d_entry_type(const struct dentry *dentry)
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{
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return dentry->d_flags & DCACHE_ENTRY_TYPE;
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}
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static inline bool d_is_miss(const struct dentry *dentry)
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{
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return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
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}
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static inline bool d_is_whiteout(const struct dentry *dentry)
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{
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return __d_entry_type(dentry) == DCACHE_WHITEOUT_TYPE;
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}
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static inline bool d_can_lookup(const struct dentry *dentry)
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{
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return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
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}
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static inline bool d_is_autodir(const struct dentry *dentry)
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{
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return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
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}
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static inline bool d_is_dir(const struct dentry *dentry)
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{
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return d_can_lookup(dentry) || d_is_autodir(dentry);
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}
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static inline bool d_is_symlink(const struct dentry *dentry)
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{
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return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
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}
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static inline bool d_is_reg(const struct dentry *dentry)
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{
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return __d_entry_type(dentry) == DCACHE_REGULAR_TYPE;
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}
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static inline bool d_is_special(const struct dentry *dentry)
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{
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return __d_entry_type(dentry) == DCACHE_SPECIAL_TYPE;
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}
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static inline bool d_is_file(const struct dentry *dentry)
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{
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return d_is_reg(dentry) || d_is_special(dentry);
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}
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static inline bool d_is_negative(const struct dentry *dentry)
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{
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// TODO: check d_is_whiteout(dentry) also.
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return d_is_miss(dentry);
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}
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static inline bool d_flags_negative(unsigned flags)
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{
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return (flags & DCACHE_ENTRY_TYPE) == DCACHE_MISS_TYPE;
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}
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static inline bool d_is_positive(const struct dentry *dentry)
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{
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return !d_is_negative(dentry);
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}
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/**
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* d_really_is_negative - Determine if a dentry is really negative (ignoring fallthroughs)
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* @dentry: The dentry in question
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*
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* Returns true if the dentry represents either an absent name or a name that
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* doesn't map to an inode (ie. ->d_inode is NULL). The dentry could represent
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* a true miss, a whiteout that isn't represented by a 0,0 chardev or a
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* fallthrough marker in an opaque directory.
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*
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* Note! (1) This should be used *only* by a filesystem to examine its own
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* dentries. It should not be used to look at some other filesystem's
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* dentries. (2) It should also be used in combination with d_inode() to get
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* the inode. (3) The dentry may have something attached to ->d_lower and the
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* type field of the flags may be set to something other than miss or whiteout.
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*/
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static inline bool d_really_is_negative(const struct dentry *dentry)
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{
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return dentry->d_inode == NULL;
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}
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/**
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* d_really_is_positive - Determine if a dentry is really positive (ignoring fallthroughs)
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* @dentry: The dentry in question
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*
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* Returns true if the dentry represents a name that maps to an inode
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* (ie. ->d_inode is not NULL). The dentry might still represent a whiteout if
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* that is represented on medium as a 0,0 chardev.
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*
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* Note! (1) This should be used *only* by a filesystem to examine its own
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* 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 void d_set_fallthru(struct dentry *dentry);
|
|
|
|
static inline bool d_is_fallthru(const struct dentry *dentry)
|
|
{
|
|
return dentry->d_flags & DCACHE_FALLTHRU;
|
|
}
|
|
|
|
|
|
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_backing_dentry - Get upper or lower dentry we should be using
|
|
* @upper: The upper layer
|
|
*
|
|
* This is the helper that should be used to get the dentry of the inode that
|
|
* will be used if this dentry were opened as a file. It may be the upper
|
|
* dentry or it may be a lower dentry pinned by the upper.
|
|
*
|
|
* Normal filesystems should not use this to access their own dentries.
|
|
*/
|
|
static inline struct dentry *d_backing_dentry(struct dentry *upper)
|
|
{
|
|
return upper;
|
|
}
|
|
|
|
/**
|
|
* d_real - Return the real dentry
|
|
* @dentry: the dentry to query
|
|
* @inode: inode to select the dentry from multiple layers (can be NULL)
|
|
*
|
|
* 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,
|
|
const struct inode *inode)
|
|
{
|
|
if (unlikely(dentry->d_flags & DCACHE_OP_REAL))
|
|
return dentry->d_op->d_real(dentry, inode);
|
|
else
|
|
return dentry;
|
|
}
|
|
|
|
/**
|
|
* d_real_inode - Return the real inode
|
|
* @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_backing_inode(d_real((struct dentry *) dentry, NULL));
|
|
}
|
|
|
|
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 *);
|
|
|
|
#endif /* __LINUX_DCACHE_H */
|