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#ifndef __LINUX_DCACHE_H #define __LINUX_DCACHE_H #ifdef __KERNEL__ #include <asm/atomic.h> #include <linux/list.h> #include <linux/spinlock.h> #include <linux/cache.h> #include <linux/rcupdate.h> struct nameidata; 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) /* * "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 { unsigned int hash; unsigned int len; const unsigned char *name; }; 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 /* 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. */ static inline unsigned int full_name_hash(const unsigned char *name, unsigned int len) { unsigned long hash = init_name_hash(); while (len--) hash = partial_name_hash(*name++, hash); return end_name_hash(hash); } struct dcookie_struct; #define DNAME_INLINE_LEN_MIN 36 struct dentry { atomic_t d_count; unsigned int d_flags; /* protected by d_lock */ spinlock_t d_lock; /* per dentry lock */ struct inode *d_inode; /* Where the name belongs to - NULL is * negative */ /* * The next three fields are touched by __d_lookup. Place them here * so they all fit in a cache line. */ struct hlist_node d_hash; /* lookup hash list */ struct dentry *d_parent; /* parent directory */ struct qstr d_name; struct list_head d_lru; /* LRU list */ /* * d_child and d_rcu can share memory */ union { struct list_head d_child; /* child of parent list */ struct rcu_head d_rcu; } d_u; struct list_head d_subdirs; /* our children */ struct list_head d_alias; /* inode alias list */ unsigned long d_time; /* used by d_revalidate */ struct dentry_operations *d_op; struct super_block *d_sb; /* The root of the dentry tree */ void *d_fsdata; /* fs-specific data */ #ifdef CONFIG_PROFILING struct dcookie_struct *d_cookie; /* cookie, if any */ #endif int d_mounted; unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */ }; struct dentry_operations { int (*d_revalidate)(struct dentry *, struct nameidata *); int (*d_hash) (struct dentry *, struct qstr *); int (*d_compare) (struct dentry *, struct qstr *, struct qstr *); int (*d_delete)(struct dentry *); void (*d_release)(struct dentry *); void (*d_iput)(struct dentry *, struct inode *); }; /* the dentry parameter passed to d_hash and d_compare is the parent * directory of the entries to be compared. It is used in case these * functions need any directory specific information for determining * equivalency classes. Using the dentry itself might not work, as it * might be a negative dentry which has no information associated with * it */ /* locking rules: big lock dcache_lock d_lock may block d_revalidate: no no no yes d_hash no no no yes d_compare: no yes yes no d_delete: no yes no no d_release: no no no yes d_iput: no no no yes */ /* d_flags entries */ #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */ #define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly * renamed" and has to be * deleted on the last dput() */ #define DCACHE_DISCONNECTED 0x0004 /* 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 0x0008 /* Recently used, don't discard. */ #define DCACHE_UNHASHED 0x0010 extern spinlock_t dcache_lock; /** * d_drop - drop a dentry * @dentry: dentry to drop * * d_drop() unhashes the entry from the parent dentry hashes, so that it won't * be found through a VFS lookup any more. Note that this is different from * deleting the dentry - d_delete will try to mark the dentry negative if * possible, giving a successful _negative_ lookup, while d_drop will * just make the cache lookup fail. * * d_drop() is used mainly for stuff that wants to invalidate a dentry for some * reason (NFS timeouts or autofs deletes). * * __d_drop requires dentry->d_lock. */ static inline void __d_drop(struct dentry *dentry) { if (!(dentry->d_flags & DCACHE_UNHASHED)) { dentry->d_flags |= DCACHE_UNHASHED; hlist_del_rcu(&dentry->d_hash); } } static inline void d_drop(struct dentry *dentry) { spin_lock(&dcache_lock); spin_lock(&dentry->d_lock); __d_drop(dentry); spin_unlock(&dentry->d_lock); spin_unlock(&dcache_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 void d_delete(struct dentry *); /* allocate/de-allocate */ extern struct dentry * d_alloc(struct dentry *, const struct qstr *); extern struct dentry * d_alloc_anon(struct inode *); extern struct dentry * d_splice_alias(struct inode *, struct dentry *); extern void shrink_dcache_sb(struct super_block *); extern void shrink_dcache_parent(struct dentry *); extern void shrink_dcache_anon(struct hlist_head *); extern int d_invalidate(struct dentry *); /* only used at mount-time */ extern struct dentry * d_alloc_root(struct inode *); /* <clickety>-<click> the ramfs-type tree */ extern void d_genocide(struct dentry *); extern struct dentry *d_find_alias(struct inode *); extern void d_prune_aliases(struct inode *); /* test whether we have any submounts in a subdir tree */ extern int have_submounts(struct dentry *); /* * 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; } /* used for rename() and baskets */ extern void d_move(struct dentry *, struct dentry *); /* appendix may either be NULL or be used for transname suffixes */ extern struct dentry * d_lookup(struct dentry *, struct qstr *); extern struct dentry * __d_lookup(struct dentry *, struct qstr *); /* validate "insecure" dentry pointer */ extern int d_validate(struct dentry *, struct dentry *); extern char * d_path(struct dentry *, struct vfsmount *, char *, int); /* Allocation counts.. */ /** * dget, dget_locked - 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. dget() should never be * called for dentries with zero reference counter. For these cases * (preferably none, functions in dcache.c are sufficient for normal * needs and they take necessary precautions) you should hold dcache_lock * and call dget_locked() instead of dget(). */ static inline struct dentry *dget(struct dentry *dentry) { if (dentry) { BUG_ON(!atomic_read(&dentry->d_count)); atomic_inc(&dentry->d_count); } return dentry; } extern struct dentry * dget_locked(struct 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(struct dentry *dentry) { return (dentry->d_flags & DCACHE_UNHASHED); } static inline struct dentry *dget_parent(struct dentry *dentry) { struct dentry *ret; spin_lock(&dentry->d_lock); ret = dget(dentry->d_parent); spin_unlock(&dentry->d_lock); return ret; } extern void dput(struct dentry *); static inline int d_mountpoint(struct dentry *dentry) { return dentry->d_mounted; } extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *); extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int); extern struct dentry *lookup_create(struct nameidata *nd, int is_dir); extern int sysctl_vfs_cache_pressure; #endif /* __KERNEL__ */ #endif /* __LINUX_DCACHE_H */