/* * fs/dcache.c * * Complete reimplementation * (C) 1997 Thomas Schoebel-Theuer, * with heavy changes by Linus Torvalds */ /* * Notes on the allocation strategy: * * The dcache is a master of the icache - whenever a dcache entry * exists, the inode will always exist. "iput()" is done either when * the dcache entry is deleted or garbage collected. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "internal.h" int sysctl_vfs_cache_pressure __read_mostly = 100; EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock); __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); EXPORT_SYMBOL(dcache_lock); static struct kmem_cache *dentry_cache __read_mostly; #define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname)) /* * This is the single most critical data structure when it comes * to the dcache: the hashtable for lookups. Somebody should try * to make this good - I've just made it work. * * This hash-function tries to avoid losing too many bits of hash * information, yet avoid using a prime hash-size or similar. */ #define D_HASHBITS d_hash_shift #define D_HASHMASK d_hash_mask static unsigned int d_hash_mask __read_mostly; static unsigned int d_hash_shift __read_mostly; static struct hlist_head *dentry_hashtable __read_mostly; /* Statistics gathering. */ struct dentry_stat_t dentry_stat = { .age_limit = 45, }; static void __d_free(struct dentry *dentry) { WARN_ON(!list_empty(&dentry->d_alias)); if (dname_external(dentry)) kfree(dentry->d_name.name); kmem_cache_free(dentry_cache, dentry); } static void d_callback(struct rcu_head *head) { struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu); __d_free(dentry); } /* * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry * inside dcache_lock. */ static void d_free(struct dentry *dentry) { if (dentry->d_op && dentry->d_op->d_release) dentry->d_op->d_release(dentry); /* if dentry was never inserted into hash, immediate free is OK */ if (hlist_unhashed(&dentry->d_hash)) __d_free(dentry); else call_rcu(&dentry->d_u.d_rcu, d_callback); } /* * Release the dentry's inode, using the filesystem * d_iput() operation if defined. */ static void dentry_iput(struct dentry * dentry) __releases(dentry->d_lock) __releases(dcache_lock) { struct inode *inode = dentry->d_inode; if (inode) { dentry->d_inode = NULL; list_del_init(&dentry->d_alias); spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); if (!inode->i_nlink) fsnotify_inoderemove(inode); if (dentry->d_op && dentry->d_op->d_iput) dentry->d_op->d_iput(dentry, inode); else iput(inode); } else { spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); } } /* * dentry_lru_(add|add_tail|del|del_init) must be called with dcache_lock held. */ static void dentry_lru_add(struct dentry *dentry) { list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); dentry->d_sb->s_nr_dentry_unused++; dentry_stat.nr_unused++; } static void dentry_lru_add_tail(struct dentry *dentry) { list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); dentry->d_sb->s_nr_dentry_unused++; dentry_stat.nr_unused++; } static void dentry_lru_del(struct dentry *dentry) { if (!list_empty(&dentry->d_lru)) { list_del(&dentry->d_lru); dentry->d_sb->s_nr_dentry_unused--; dentry_stat.nr_unused--; } } static void dentry_lru_del_init(struct dentry *dentry) { if (likely(!list_empty(&dentry->d_lru))) { list_del_init(&dentry->d_lru); dentry->d_sb->s_nr_dentry_unused--; dentry_stat.nr_unused--; } } /** * d_kill - kill dentry and return parent * @dentry: dentry to kill * * The dentry must already be unhashed and removed from the LRU. * * If this is the root of the dentry tree, return NULL. */ static struct dentry *d_kill(struct dentry *dentry) __releases(dentry->d_lock) __releases(dcache_lock) { struct dentry *parent; list_del(&dentry->d_u.d_child); dentry_stat.nr_dentry--; /* For d_free, below */ /*drops the locks, at that point nobody can reach this dentry */ dentry_iput(dentry); if (IS_ROOT(dentry)) parent = NULL; else parent = dentry->d_parent; d_free(dentry); return parent; } /* * This is dput * * This is complicated by the fact that we do not want to put * dentries that are no longer on any hash chain on the unused * list: we'd much rather just get rid of them immediately. * * However, that implies that we have to traverse the dentry * tree upwards to the parents which might _also_ now be * scheduled for deletion (it may have been only waiting for * its last child to go away). * * This tail recursion is done by hand as we don't want to depend * on the compiler to always get this right (gcc generally doesn't). * Real recursion would eat up our stack space. */ /* * dput - release a dentry * @dentry: dentry to release * * Release a dentry. This will drop the usage count and if appropriate * call the dentry unlink method as well as removing it from the queues and * releasing its resources. If the parent dentries were scheduled for release * they too may now get deleted. * * no dcache lock, please. */ void dput(struct dentry *dentry) { if (!dentry) return; repeat: if (atomic_read(&dentry->d_count) == 1) might_sleep(); if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock)) return; spin_lock(&dentry->d_lock); if (atomic_read(&dentry->d_count)) { spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); return; } /* * AV: ->d_delete() is _NOT_ allowed to block now. */ if (dentry->d_op && dentry->d_op->d_delete) { if (dentry->d_op->d_delete(dentry)) goto unhash_it; } /* Unreachable? Get rid of it */ if (d_unhashed(dentry)) goto kill_it; if (list_empty(&dentry->d_lru)) { dentry->d_flags |= DCACHE_REFERENCED; dentry_lru_add(dentry); } spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); return; unhash_it: __d_drop(dentry); kill_it: /* if dentry was on the d_lru list delete it from there */ dentry_lru_del(dentry); dentry = d_kill(dentry); if (dentry) goto repeat; } EXPORT_SYMBOL(dput); /** * d_invalidate - invalidate a dentry * @dentry: dentry to invalidate * * Try to invalidate the dentry if it turns out to be * possible. If there are other dentries that can be * reached through this one we can't delete it and we * return -EBUSY. On success we return 0. * * no dcache lock. */ int d_invalidate(struct dentry * dentry) { /* * If it's already been dropped, return OK. */ spin_lock(&dcache_lock); if (d_unhashed(dentry)) { spin_unlock(&dcache_lock); return 0; } /* * Check whether to do a partial shrink_dcache * to get rid of unused child entries. */ if (!list_empty(&dentry->d_subdirs)) { spin_unlock(&dcache_lock); shrink_dcache_parent(dentry); spin_lock(&dcache_lock); } /* * Somebody else still using it? * * If it's a directory, we can't drop it * for fear of somebody re-populating it * with children (even though dropping it * would make it unreachable from the root, * we might still populate it if it was a * working directory or similar). */ spin_lock(&dentry->d_lock); if (atomic_read(&dentry->d_count) > 1) { if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) { spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); return -EBUSY; } } __d_drop(dentry); spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); return 0; } EXPORT_SYMBOL(d_invalidate); /* This should be called _only_ with dcache_lock held */ static inline struct dentry * __dget_locked(struct dentry *dentry) { atomic_inc(&dentry->d_count); dentry_lru_del_init(dentry); return dentry; } struct dentry * dget_locked(struct dentry *dentry) { return __dget_locked(dentry); } EXPORT_SYMBOL(dget_locked); /** * d_find_alias - grab a hashed alias of inode * @inode: inode in question * @want_discon: flag, used by d_splice_alias, to request * that only a DISCONNECTED alias be returned. * * If inode has a hashed alias, or is a directory and has any alias, * acquire the reference to alias and return it. Otherwise return NULL. * Notice that if inode is a directory there can be only one alias and * it can be unhashed only if it has no children, or if it is the root * of a filesystem. * * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer * any other hashed alias over that one unless @want_discon is set, * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias. */ static struct dentry * __d_find_alias(struct inode *inode, int want_discon) { struct list_head *head, *next, *tmp; struct dentry *alias, *discon_alias=NULL; head = &inode->i_dentry; next = inode->i_dentry.next; while (next != head) { tmp = next; next = tmp->next; prefetch(next); alias = list_entry(tmp, struct dentry, d_alias); if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { if (IS_ROOT(alias) && (alias->d_flags & DCACHE_DISCONNECTED)) discon_alias = alias; else if (!want_discon) { __dget_locked(alias); return alias; } } } if (discon_alias) __dget_locked(discon_alias); return discon_alias; } struct dentry * d_find_alias(struct inode *inode) { struct dentry *de = NULL; if (!list_empty(&inode->i_dentry)) { spin_lock(&dcache_lock); de = __d_find_alias(inode, 0); spin_unlock(&dcache_lock); } return de; } EXPORT_SYMBOL(d_find_alias); /* * Try to kill dentries associated with this inode. * WARNING: you must own a reference to inode. */ void d_prune_aliases(struct inode *inode) { struct dentry *dentry; restart: spin_lock(&dcache_lock); list_for_each_entry(dentry, &inode->i_dentry, d_alias) { spin_lock(&dentry->d_lock); if (!atomic_read(&dentry->d_count)) { __dget_locked(dentry); __d_drop(dentry); spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); dput(dentry); goto restart; } spin_unlock(&dentry->d_lock); } spin_unlock(&dcache_lock); } EXPORT_SYMBOL(d_prune_aliases); /* * Throw away a dentry - free the inode, dput the parent. This requires that * the LRU list has already been removed. * * Try to prune ancestors as well. This is necessary to prevent * quadratic behavior of shrink_dcache_parent(), but is also expected * to be beneficial in reducing dentry cache fragmentation. */ static void prune_one_dentry(struct dentry * dentry) __releases(dentry->d_lock) __releases(dcache_lock) __acquires(dcache_lock) { __d_drop(dentry); dentry = d_kill(dentry); /* * Prune ancestors. Locking is simpler than in dput(), * because dcache_lock needs to be taken anyway. */ spin_lock(&dcache_lock); while (dentry) { if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock)) return; if (dentry->d_op && dentry->d_op->d_delete) dentry->d_op->d_delete(dentry); dentry_lru_del_init(dentry); __d_drop(dentry); dentry = d_kill(dentry); spin_lock(&dcache_lock); } } /* * Shrink the dentry LRU on a given superblock. * @sb : superblock to shrink dentry LRU. * @count: If count is NULL, we prune all dentries on superblock. * @flags: If flags is non-zero, we need to do special processing based on * which flags are set. This means we don't need to maintain multiple * similar copies of this loop. */ static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags) { LIST_HEAD(referenced); LIST_HEAD(tmp); struct dentry *dentry; int cnt = 0; BUG_ON(!sb); BUG_ON((flags & DCACHE_REFERENCED) && count == NULL); spin_lock(&dcache_lock); if (count != NULL) /* called from prune_dcache() and shrink_dcache_parent() */ cnt = *count; restart: if (count == NULL) list_splice_init(&sb->s_dentry_lru, &tmp); else { while (!list_empty(&sb->s_dentry_lru)) { dentry = list_entry(sb->s_dentry_lru.prev, struct dentry, d_lru); BUG_ON(dentry->d_sb != sb); spin_lock(&dentry->d_lock); /* * If we are honouring the DCACHE_REFERENCED flag and * the dentry has this flag set, don't free it. Clear * the flag and put it back on the LRU. */ if ((flags & DCACHE_REFERENCED) && (dentry->d_flags & DCACHE_REFERENCED)) { dentry->d_flags &= ~DCACHE_REFERENCED; list_move(&dentry->d_lru, &referenced); spin_unlock(&dentry->d_lock); } else { list_move_tail(&dentry->d_lru, &tmp); spin_unlock(&dentry->d_lock); cnt--; if (!cnt) break; } cond_resched_lock(&dcache_lock); } } while (!list_empty(&tmp)) { dentry = list_entry(tmp.prev, struct dentry, d_lru); dentry_lru_del_init(dentry); spin_lock(&dentry->d_lock); /* * We found an inuse dentry which was not removed from * the LRU because of laziness during lookup. Do not free * it - just keep it off the LRU list. */ if (atomic_read(&dentry->d_count)) { spin_unlock(&dentry->d_lock); continue; } prune_one_dentry(dentry); /* dentry->d_lock was dropped in prune_one_dentry() */ cond_resched_lock(&dcache_lock); } if (count == NULL && !list_empty(&sb->s_dentry_lru)) goto restart; if (count != NULL) *count = cnt; if (!list_empty(&referenced)) list_splice(&referenced, &sb->s_dentry_lru); spin_unlock(&dcache_lock); } /** * prune_dcache - shrink the dcache * @count: number of entries to try to free * * Shrink the dcache. This is done when we need more memory, or simply when we * need to unmount something (at which point we need to unuse all dentries). * * This function may fail to free any resources if all the dentries are in use. */ static void prune_dcache(int count) { struct super_block *sb, *p = NULL; int w_count; int unused = dentry_stat.nr_unused; int prune_ratio; int pruned; if (unused == 0 || count == 0) return; spin_lock(&dcache_lock); if (count >= unused) prune_ratio = 1; else prune_ratio = unused / count; spin_lock(&sb_lock); list_for_each_entry(sb, &super_blocks, s_list) { if (list_empty(&sb->s_instances)) continue; if (sb->s_nr_dentry_unused == 0) continue; sb->s_count++; /* Now, we reclaim unused dentrins with fairness. * We reclaim them same percentage from each superblock. * We calculate number of dentries to scan on this sb * as follows, but the implementation is arranged to avoid * overflows: * number of dentries to scan on this sb = * count * (number of dentries on this sb / * number of dentries in the machine) */ spin_unlock(&sb_lock); if (prune_ratio != 1) w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1; else w_count = sb->s_nr_dentry_unused; pruned = w_count; /* * We need to be sure this filesystem isn't being unmounted, * otherwise we could race with generic_shutdown_super(), and * end up holding a reference to an inode while the filesystem * is unmounted. So we try to get s_umount, and make sure * s_root isn't NULL. */ if (down_read_trylock(&sb->s_umount)) { if ((sb->s_root != NULL) && (!list_empty(&sb->s_dentry_lru))) { spin_unlock(&dcache_lock); __shrink_dcache_sb(sb, &w_count, DCACHE_REFERENCED); pruned -= w_count; spin_lock(&dcache_lock); } up_read(&sb->s_umount); } spin_lock(&sb_lock); if (p) __put_super(p); count -= pruned; p = sb; /* more work left to do? */ if (count <= 0) break; } if (p) __put_super(p); spin_unlock(&sb_lock); spin_unlock(&dcache_lock); } /** * shrink_dcache_sb - shrink dcache for a superblock * @sb: superblock * * Shrink the dcache for the specified super block. This * is used to free the dcache before unmounting a file * system */ void shrink_dcache_sb(struct super_block * sb) { __shrink_dcache_sb(sb, NULL, 0); } EXPORT_SYMBOL(shrink_dcache_sb); /* * destroy a single subtree of dentries for unmount * - see the comments on shrink_dcache_for_umount() for a description of the * locking */ static void shrink_dcache_for_umount_subtree(struct dentry *dentry) { struct dentry *parent; unsigned detached = 0; BUG_ON(!IS_ROOT(dentry)); /* detach this root from the system */ spin_lock(&dcache_lock); dentry_lru_del_init(dentry); __d_drop(dentry); spin_unlock(&dcache_lock); for (;;) { /* descend to the first leaf in the current subtree */ while (!list_empty(&dentry->d_subdirs)) { struct dentry *loop; /* this is a branch with children - detach all of them * from the system in one go */ spin_lock(&dcache_lock); list_for_each_entry(loop, &dentry->d_subdirs, d_u.d_child) { dentry_lru_del_init(loop); __d_drop(loop); cond_resched_lock(&dcache_lock); } spin_unlock(&dcache_lock); /* move to the first child */ dentry = list_entry(dentry->d_subdirs.next, struct dentry, d_u.d_child); } /* consume the dentries from this leaf up through its parents * until we find one with children or run out altogether */ do { struct inode *inode; if (atomic_read(&dentry->d_count) != 0) { printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%s}" " still in use (%d)" " [unmount of %s %s]\n", dentry, dentry->d_inode ? dentry->d_inode->i_ino : 0UL, dentry->d_name.name, atomic_read(&dentry->d_count), dentry->d_sb->s_type->name, dentry->d_sb->s_id); BUG(); } if (IS_ROOT(dentry)) parent = NULL; else { parent = dentry->d_parent; atomic_dec(&parent->d_count); } list_del(&dentry->d_u.d_child); detached++; inode = dentry->d_inode; if (inode) { dentry->d_inode = NULL; list_del_init(&dentry->d_alias); if (dentry->d_op && dentry->d_op->d_iput) dentry->d_op->d_iput(dentry, inode); else iput(inode); } d_free(dentry); /* finished when we fall off the top of the tree, * otherwise we ascend to the parent and move to the * next sibling if there is one */ if (!parent) goto out; dentry = parent; } while (list_empty(&dentry->d_subdirs)); dentry = list_entry(dentry->d_subdirs.next, struct dentry, d_u.d_child); } out: /* several dentries were freed, need to correct nr_dentry */ spin_lock(&dcache_lock); dentry_stat.nr_dentry -= detached; spin_unlock(&dcache_lock); } /* * destroy the dentries attached to a superblock on unmounting * - we don't need to use dentry->d_lock, and only need dcache_lock when * removing the dentry from the system lists and hashes because: * - the superblock is detached from all mountings and open files, so the * dentry trees will not be rearranged by the VFS * - s_umount is write-locked, so the memory pressure shrinker will ignore * any dentries belonging to this superblock that it comes across * - the filesystem itself is no longer permitted to rearrange the dentries * in this superblock */ void shrink_dcache_for_umount(struct super_block *sb) { struct dentry *dentry; if (down_read_trylock(&sb->s_umount)) BUG(); dentry = sb->s_root; sb->s_root = NULL; atomic_dec(&dentry->d_count); shrink_dcache_for_umount_subtree(dentry); while (!hlist_empty(&sb->s_anon)) { dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash); shrink_dcache_for_umount_subtree(dentry); } } /* * Search for at least 1 mount point in the dentry's subdirs. * We descend to the next level whenever the d_subdirs * list is non-empty and continue searching. */ /** * have_submounts - check for mounts over a dentry * @parent: dentry to check. * * Return true if the parent or its subdirectories contain * a mount point */ int have_submounts(struct dentry *parent) { struct dentry *this_parent = parent; struct list_head *next; spin_lock(&dcache_lock); if (d_mountpoint(parent)) goto positive; repeat: next = this_parent->d_subdirs.next; resume: while (next != &this_parent->d_subdirs) { struct list_head *tmp = next; struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); next = tmp->next; /* Have we found a mount point ? */ if (d_mountpoint(dentry)) goto positive; if (!list_empty(&dentry->d_subdirs)) { this_parent = dentry; goto repeat; } } /* * All done at this level ... ascend and resume the search. */ if (this_parent != parent) { next = this_parent->d_u.d_child.next; this_parent = this_parent->d_parent; goto resume; } spin_unlock(&dcache_lock); return 0; /* No mount points found in tree */ positive: spin_unlock(&dcache_lock); return 1; } EXPORT_SYMBOL(have_submounts); /* * Search the dentry child list for the specified parent, * and move any unused dentries to the end of the unused * list for prune_dcache(). We descend to the next level * whenever the d_subdirs list is non-empty and continue * searching. * * It returns zero iff there are no unused children, * otherwise it returns the number of children moved to * the end of the unused list. This may not be the total * number of unused children, because select_parent can * drop the lock and return early due to latency * constraints. */ static int select_parent(struct dentry * parent) { struct dentry *this_parent = parent; struct list_head *next; int found = 0; spin_lock(&dcache_lock); repeat: next = this_parent->d_subdirs.next; resume: while (next != &this_parent->d_subdirs) { struct list_head *tmp = next; struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); next = tmp->next; dentry_lru_del_init(dentry); /* * move only zero ref count dentries to the end * of the unused list for prune_dcache */ if (!atomic_read(&dentry->d_count)) { dentry_lru_add_tail(dentry); found++; } /* * We can return to the caller if we have found some (this * ensures forward progress). We'll be coming back to find * the rest. */ if (found && need_resched()) goto out; /* * Descend a level if the d_subdirs list is non-empty. */ if (!list_empty(&dentry->d_subdirs)) { this_parent = dentry; goto repeat; } } /* * All done at this level ... ascend and resume the search. */ if (this_parent != parent) { next = this_parent->d_u.d_child.next; this_parent = this_parent->d_parent; goto resume; } out: spin_unlock(&dcache_lock); return found; } /** * shrink_dcache_parent - prune dcache * @parent: parent of entries to prune * * Prune the dcache to remove unused children of the parent dentry. */ void shrink_dcache_parent(struct dentry * parent) { struct super_block *sb = parent->d_sb; int found; while ((found = select_parent(parent)) != 0) __shrink_dcache_sb(sb, &found, 0); } EXPORT_SYMBOL(shrink_dcache_parent); /* * Scan `nr' dentries and return the number which remain. * * We need to avoid reentering the filesystem if the caller is performing a * GFP_NOFS allocation attempt. One example deadlock is: * * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache-> * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode-> * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK. * * In this case we return -1 to tell the caller that we baled. */ static int shrink_dcache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask) { if (nr) { if (!(gfp_mask & __GFP_FS)) return -1; prune_dcache(nr); } return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure; } static struct shrinker dcache_shrinker = { .shrink = shrink_dcache_memory, .seeks = DEFAULT_SEEKS, }; /** * d_alloc - allocate a dcache entry * @parent: parent of entry to allocate * @name: qstr of the name * * Allocates a dentry. It returns %NULL if there is insufficient memory * available. On a success the dentry is returned. The name passed in is * copied and the copy passed in may be reused after this call. */ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) { struct dentry *dentry; char *dname; dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); if (!dentry) return NULL; if (name->len > DNAME_INLINE_LEN-1) { dname = kmalloc(name->len + 1, GFP_KERNEL); if (!dname) { kmem_cache_free(dentry_cache, dentry); return NULL; } } else { dname = dentry->d_iname; } dentry->d_name.name = dname; dentry->d_name.len = name->len; dentry->d_name.hash = name->hash; memcpy(dname, name->name, name->len); dname[name->len] = 0; atomic_set(&dentry->d_count, 1); dentry->d_flags = DCACHE_UNHASHED; spin_lock_init(&dentry->d_lock); dentry->d_inode = NULL; dentry->d_parent = NULL; dentry->d_sb = NULL; dentry->d_op = NULL; dentry->d_fsdata = NULL; dentry->d_mounted = 0; INIT_HLIST_NODE(&dentry->d_hash); INIT_LIST_HEAD(&dentry->d_lru); INIT_LIST_HEAD(&dentry->d_subdirs); INIT_LIST_HEAD(&dentry->d_alias); if (parent) { dentry->d_parent = dget(parent); dentry->d_sb = parent->d_sb; } else { INIT_LIST_HEAD(&dentry->d_u.d_child); } spin_lock(&dcache_lock); if (parent) list_add(&dentry->d_u.d_child, &parent->d_subdirs); dentry_stat.nr_dentry++; spin_unlock(&dcache_lock); return dentry; } EXPORT_SYMBOL(d_alloc); struct dentry *d_alloc_name(struct dentry *parent, const char *name) { struct qstr q; q.name = name; q.len = strlen(name); q.hash = full_name_hash(q.name, q.len); return d_alloc(parent, &q); } EXPORT_SYMBOL(d_alloc_name); /* the caller must hold dcache_lock */ static void __d_instantiate(struct dentry *dentry, struct inode *inode) { if (inode) list_add(&dentry->d_alias, &inode->i_dentry); dentry->d_inode = inode; fsnotify_d_instantiate(dentry, inode); } /** * d_instantiate - fill in inode information for a dentry * @entry: dentry to complete * @inode: inode to attach to this dentry * * Fill in inode information in the entry. * * This turns negative dentries into productive full members * of society. * * NOTE! This assumes that the inode count has been incremented * (or otherwise set) by the caller to indicate that it is now * in use by the dcache. */ void d_instantiate(struct dentry *entry, struct inode * inode) { BUG_ON(!list_empty(&entry->d_alias)); spin_lock(&dcache_lock); __d_instantiate(entry, inode); spin_unlock(&dcache_lock); security_d_instantiate(entry, inode); } EXPORT_SYMBOL(d_instantiate); /** * d_instantiate_unique - instantiate a non-aliased dentry * @entry: dentry to instantiate * @inode: inode to attach to this dentry * * Fill in inode information in the entry. On success, it returns NULL. * If an unhashed alias of "entry" already exists, then we return the * aliased dentry instead and drop one reference to inode. * * Note that in order to avoid conflicts with rename() etc, the caller * had better be holding the parent directory semaphore. * * This also assumes that the inode count has been incremented * (or otherwise set) by the caller to indicate that it is now * in use by the dcache. */ static struct dentry *__d_instantiate_unique(struct dentry *entry, struct inode *inode) { struct dentry *alias; int len = entry->d_name.len; const char *name = entry->d_name.name; unsigned int hash = entry->d_name.hash; if (!inode) { __d_instantiate(entry, NULL); return NULL; } list_for_each_entry(alias, &inode->i_dentry, d_alias) { struct qstr *qstr = &alias->d_name; if (qstr->hash != hash) continue; if (alias->d_parent != entry->d_parent) continue; if (qstr->len != len) continue; if (memcmp(qstr->name, name, len)) continue; dget_locked(alias); return alias; } __d_instantiate(entry, inode); return NULL; } struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode) { struct dentry *result; BUG_ON(!list_empty(&entry->d_alias)); spin_lock(&dcache_lock); result = __d_instantiate_unique(entry, inode); spin_unlock(&dcache_lock); if (!result) { security_d_instantiate(entry, inode); return NULL; } BUG_ON(!d_unhashed(result)); iput(inode); return result; } EXPORT_SYMBOL(d_instantiate_unique); /** * d_alloc_root - allocate root dentry * @root_inode: inode to allocate the root for * * Allocate a root ("/") dentry for the inode given. The inode is * instantiated and returned. %NULL is returned if there is insufficient * memory or the inode passed is %NULL. */ struct dentry * d_alloc_root(struct inode * root_inode) { struct dentry *res = NULL; if (root_inode) { static const struct qstr name = { .name = "/", .len = 1 }; res = d_alloc(NULL, &name); if (res) { res->d_sb = root_inode->i_sb; res->d_parent = res; d_instantiate(res, root_inode); } } return res; } EXPORT_SYMBOL(d_alloc_root); static inline struct hlist_head *d_hash(struct dentry *parent, unsigned long hash) { hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES; hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS); return dentry_hashtable + (hash & D_HASHMASK); } /** * d_obtain_alias - find or allocate a dentry for a given inode * @inode: inode to allocate the dentry for * * Obtain a dentry for an inode resulting from NFS filehandle conversion or * similar open by handle operations. The returned dentry may be anonymous, * or may have a full name (if the inode was already in the cache). * * When called on a directory inode, we must ensure that the inode only ever * has one dentry. If a dentry is found, that is returned instead of * allocating a new one. * * On successful return, the reference to the inode has been transferred * to the dentry. In case of an error the reference on the inode is released. * To make it easier to use in export operations a %NULL or IS_ERR inode may * be passed in and will be the error will be propagate to the return value, * with a %NULL @inode replaced by ERR_PTR(-ESTALE). */ struct dentry *d_obtain_alias(struct inode *inode) { static const struct qstr anonstring = { .name = "" }; struct dentry *tmp; struct dentry *res; if (!inode) return ERR_PTR(-ESTALE); if (IS_ERR(inode)) return ERR_CAST(inode); res = d_find_alias(inode); if (res) goto out_iput; tmp = d_alloc(NULL, &anonstring); if (!tmp) { res = ERR_PTR(-ENOMEM); goto out_iput; } tmp->d_parent = tmp; /* make sure dput doesn't croak */ spin_lock(&dcache_lock); res = __d_find_alias(inode, 0); if (res) { spin_unlock(&dcache_lock); dput(tmp); goto out_iput; } /* attach a disconnected dentry */ spin_lock(&tmp->d_lock); tmp->d_sb = inode->i_sb; tmp->d_inode = inode; tmp->d_flags |= DCACHE_DISCONNECTED; tmp->d_flags &= ~DCACHE_UNHASHED; list_add(&tmp->d_alias, &inode->i_dentry); hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon); spin_unlock(&tmp->d_lock); spin_unlock(&dcache_lock); return tmp; out_iput: iput(inode); return res; } EXPORT_SYMBOL(d_obtain_alias); /** * d_splice_alias - splice a disconnected dentry into the tree if one exists * @inode: the inode which may have a disconnected dentry * @dentry: a negative dentry which we want to point to the inode. * * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and * DCACHE_DISCONNECTED), then d_move that in place of the given dentry * and return it, else simply d_add the inode to the dentry and return NULL. * * This is needed in the lookup routine of any filesystem that is exportable * (via knfsd) so that we can build dcache paths to directories effectively. * * If a dentry was found and moved, then it is returned. Otherwise NULL * is returned. This matches the expected return value of ->lookup. * */ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) { struct dentry *new = NULL; if (inode && S_ISDIR(inode->i_mode)) { spin_lock(&dcache_lock); new = __d_find_alias(inode, 1); if (new) { BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); spin_unlock(&dcache_lock); security_d_instantiate(new, inode); d_move(new, dentry); iput(inode); } else { /* already taking dcache_lock, so d_add() by hand */ __d_instantiate(dentry, inode); spin_unlock(&dcache_lock); security_d_instantiate(dentry, inode); d_rehash(dentry); } } else d_add(dentry, inode); return new; } EXPORT_SYMBOL(d_splice_alias); /** * d_add_ci - lookup or allocate new dentry with case-exact name * @inode: the inode case-insensitive lookup has found * @dentry: the negative dentry that was passed to the parent's lookup func * @name: the case-exact name to be associated with the returned dentry * * This is to avoid filling the dcache with case-insensitive names to the * same inode, only the actual correct case is stored in the dcache for * case-insensitive filesystems. * * For a case-insensitive lookup match and if the the case-exact dentry * already exists in in the dcache, use it and return it. * * If no entry exists with the exact case name, allocate new dentry with * the exact case, and return the spliced entry. */ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, struct qstr *name) { int error; struct dentry *found; struct dentry *new; /* * First check if a dentry matching the name already exists, * if not go ahead and create it now. */ found = d_hash_and_lookup(dentry->d_parent, name); if (!found) { new = d_alloc(dentry->d_parent, name); if (!new) { error = -ENOMEM; goto err_out; } found = d_splice_alias(inode, new); if (found) { dput(new); return found; } return new; } /* * If a matching dentry exists, and it's not negative use it. * * Decrement the reference count to balance the iget() done * earlier on. */ if (found->d_inode) { if (unlikely(found->d_inode != inode)) { /* This can't happen because bad inodes are unhashed. */ BUG_ON(!is_bad_inode(inode)); BUG_ON(!is_bad_inode(found->d_inode)); } iput(inode); return found; } /* * Negative dentry: instantiate it unless the inode is a directory and * already has a dentry. */ spin_lock(&dcache_lock); if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) { __d_instantiate(found, inode); spin_unlock(&dcache_lock); security_d_instantiate(found, inode); return found; } /* * In case a directory already has a (disconnected) entry grab a * reference to it, move it in place and use it. */ new = list_entry(inode->i_dentry.next, struct dentry, d_alias); dget_locked(new); spin_unlock(&dcache_lock); security_d_instantiate(found, inode); d_move(new, found); iput(inode); dput(found); return new; err_out: iput(inode); return ERR_PTR(error); } EXPORT_SYMBOL(d_add_ci); /** * d_lookup - search for a dentry * @parent: parent dentry * @name: qstr of name we wish to find * * Searches the children of the parent dentry for the name in question. If * the dentry is found its reference count is incremented and the dentry * is returned. The caller must use dput to free the entry when it has * finished using it. %NULL is returned on failure. * * __d_lookup is dcache_lock free. The hash list is protected using RCU. * Memory barriers are used while updating and doing lockless traversal. * To avoid races with d_move while rename is happening, d_lock is used. * * Overflows in memcmp(), while d_move, are avoided by keeping the length * and name pointer in one structure pointed by d_qstr. * * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while * lookup is going on. * * The dentry unused LRU is not updated even if lookup finds the required dentry * in there. It is updated in places such as prune_dcache, shrink_dcache_sb, * select_parent and __dget_locked. This laziness saves lookup from dcache_lock * acquisition. * * d_lookup() is protected against the concurrent renames in some unrelated * directory using the seqlockt_t rename_lock. */ struct dentry * d_lookup(struct dentry * parent, struct qstr * name) { struct dentry * dentry = NULL; unsigned long seq; do { seq = read_seqbegin(&rename_lock); dentry = __d_lookup(parent, name); if (dentry) break; } while (read_seqretry(&rename_lock, seq)); return dentry; } EXPORT_SYMBOL(d_lookup); struct dentry * __d_lookup(struct dentry * parent, struct qstr * name) { unsigned int len = name->len; unsigned int hash = name->hash; const unsigned char *str = name->name; struct hlist_head *head = d_hash(parent,hash); struct dentry *found = NULL; struct hlist_node *node; struct dentry *dentry; rcu_read_lock(); hlist_for_each_entry_rcu(dentry, node, head, d_hash) { struct qstr *qstr; if (dentry->d_name.hash != hash) continue; if (dentry->d_parent != parent) continue; spin_lock(&dentry->d_lock); /* * Recheck the dentry after taking the lock - d_move may have * changed things. Don't bother checking the hash because we're * about to compare the whole name anyway. */ if (dentry->d_parent != parent) goto next; /* non-existing due to RCU? */ if (d_unhashed(dentry)) goto next; /* * It is safe to compare names since d_move() cannot * change the qstr (protected by d_lock). */ qstr = &dentry->d_name; if (parent->d_op && parent->d_op->d_compare) { if (parent->d_op->d_compare(parent, qstr, name)) goto next; } else { if (qstr->len != len) goto next; if (memcmp(qstr->name, str, len)) goto next; } atomic_inc(&dentry->d_count); found = dentry; spin_unlock(&dentry->d_lock); break; next: spin_unlock(&dentry->d_lock); } rcu_read_unlock(); return found; } /** * d_hash_and_lookup - hash the qstr then search for a dentry * @dir: Directory to search in * @name: qstr of name we wish to find * * On hash failure or on lookup failure NULL is returned. */ struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) { struct dentry *dentry = NULL; /* * Check for a fs-specific hash function. Note that we must * calculate the standard hash first, as the d_op->d_hash() * routine may choose to leave the hash value unchanged. */ name->hash = full_name_hash(name->name, name->len); if (dir->d_op && dir->d_op->d_hash) { if (dir->d_op->d_hash(dir, name) < 0) goto out; } dentry = d_lookup(dir, name); out: return dentry; } /** * d_validate - verify dentry provided from insecure source * @dentry: The dentry alleged to be valid child of @dparent * @dparent: The parent dentry (known to be valid) * * An insecure source has sent us a dentry, here we verify it and dget() it. * This is used by ncpfs in its readdir implementation. * Zero is returned in the dentry is invalid. */ int d_validate(struct dentry *dentry, struct dentry *dparent) { struct hlist_head *base; struct hlist_node *lhp; /* Check whether the ptr might be valid at all.. */ if (!kmem_ptr_validate(dentry_cache, dentry)) goto out; if (dentry->d_parent != dparent) goto out; spin_lock(&dcache_lock); base = d_hash(dparent, dentry->d_name.hash); hlist_for_each(lhp,base) { /* hlist_for_each_entry_rcu() not required for d_hash list * as it is parsed under dcache_lock */ if (dentry == hlist_entry(lhp, struct dentry, d_hash)) { __dget_locked(dentry); spin_unlock(&dcache_lock); return 1; } } spin_unlock(&dcache_lock); out: return 0; } EXPORT_SYMBOL(d_validate); /* * When a file is deleted, we have two options: * - turn this dentry into a negative dentry * - unhash this dentry and free it. * * Usually, we want to just turn this into * a negative dentry, but if anybody else is * currently using the dentry or the inode * we can't do that and we fall back on removing * it from the hash queues and waiting for * it to be deleted later when it has no users */ /** * d_delete - delete a dentry * @dentry: The dentry to delete * * Turn the dentry into a negative dentry if possible, otherwise * remove it from the hash queues so it can be deleted later */ void d_delete(struct dentry * dentry) { int isdir = 0; /* * Are we the only user? */ spin_lock(&dcache_lock); spin_lock(&dentry->d_lock); isdir = S_ISDIR(dentry->d_inode->i_mode); if (atomic_read(&dentry->d_count) == 1) { dentry->d_flags &= ~DCACHE_CANT_MOUNT; dentry_iput(dentry); fsnotify_nameremove(dentry, isdir); return; } if (!d_unhashed(dentry)) __d_drop(dentry); spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); fsnotify_nameremove(dentry, isdir); } EXPORT_SYMBOL(d_delete); static void __d_rehash(struct dentry * entry, struct hlist_head *list) { entry->d_flags &= ~DCACHE_UNHASHED; hlist_add_head_rcu(&entry->d_hash, list); } static void _d_rehash(struct dentry * entry) { __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash)); } /** * d_rehash - add an entry back to the hash * @entry: dentry to add to the hash * * Adds a dentry to the hash according to its name. */ void d_rehash(struct dentry * entry) { spin_lock(&dcache_lock); spin_lock(&entry->d_lock); _d_rehash(entry); spin_unlock(&entry->d_lock); spin_unlock(&dcache_lock); } EXPORT_SYMBOL(d_rehash); /* * When switching names, the actual string doesn't strictly have to * be preserved in the target - because we're dropping the target * anyway. As such, we can just do a simple memcpy() to copy over * the new name before we switch. * * Note that we have to be a lot more careful about getting the hash * switched - we have to switch the hash value properly even if it * then no longer matches the actual (corrupted) string of the target. * The hash value has to match the hash queue that the dentry is on.. */ static void switch_names(struct dentry *dentry, struct dentry *target) { if (dname_external(target)) { if (dname_external(dentry)) { /* * Both external: swap the pointers */ swap(target->d_name.name, dentry->d_name.name); } else { /* * dentry:internal, target:external. Steal target's * storage and make target internal. */ memcpy(target->d_iname, dentry->d_name.name, dentry->d_name.len + 1); dentry->d_name.name = target->d_name.name; target->d_name.name = target->d_iname; } } else { if (dname_external(dentry)) { /* * dentry:external, target:internal. Give dentry's * storage to target and make dentry internal */ memcpy(dentry->d_iname, target->d_name.name, target->d_name.len + 1); target->d_name.name = dentry->d_name.name; dentry->d_name.name = dentry->d_iname; } else { /* * Both are internal. Just copy target to dentry */ memcpy(dentry->d_iname, target->d_name.name, target->d_name.len + 1); dentry->d_name.len = target->d_name.len; return; } } swap(dentry->d_name.len, target->d_name.len); } /* * We cannibalize "target" when moving dentry on top of it, * because it's going to be thrown away anyway. We could be more * polite about it, though. * * This forceful removal will result in ugly /proc output if * somebody holds a file open that got deleted due to a rename. * We could be nicer about the deleted file, and let it show * up under the name it had before it was deleted rather than * under the original name of the file that was moved on top of it. */ /* * d_move_locked - move a dentry * @dentry: entry to move * @target: new dentry * * Update the dcache to reflect the move of a file name. Negative * dcache entries should not be moved in this way. */ static void d_move_locked(struct dentry * dentry, struct dentry * target) { struct hlist_head *list; if (!dentry->d_inode) printk(KERN_WARNING "VFS: moving negative dcache entry\n"); write_seqlock(&rename_lock); /* * XXXX: do we really need to take target->d_lock? */ if (target < dentry) { spin_lock(&target->d_lock); spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); } else { spin_lock(&dentry->d_lock); spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED); } /* Move the dentry to the target hash queue, if on different bucket */ if (d_unhashed(dentry)) goto already_unhashed; hlist_del_rcu(&dentry->d_hash); already_unhashed: list = d_hash(target->d_parent, target->d_name.hash); __d_rehash(dentry, list); /* Unhash the target: dput() will then get rid of it */ __d_drop(target); list_del(&dentry->d_u.d_child); list_del(&target->d_u.d_child); /* Switch the names.. */ switch_names(dentry, target); swap(dentry->d_name.hash, target->d_name.hash); /* ... and switch the parents */ if (IS_ROOT(dentry)) { dentry->d_parent = target->d_parent; target->d_parent = target; INIT_LIST_HEAD(&target->d_u.d_child); } else { swap(dentry->d_parent, target->d_parent); /* And add them back to the (new) parent lists */ list_add(&target->d_u.d_child, &target->d_parent->d_subdirs); } list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); spin_unlock(&target->d_lock); fsnotify_d_move(dentry); spin_unlock(&dentry->d_lock); write_sequnlock(&rename_lock); } /** * d_move - move a dentry * @dentry: entry to move * @target: new dentry * * Update the dcache to reflect the move of a file name. Negative * dcache entries should not be moved in this way. */ void d_move(struct dentry * dentry, struct dentry * target) { spin_lock(&dcache_lock); d_move_locked(dentry, target); spin_unlock(&dcache_lock); } EXPORT_SYMBOL(d_move); /** * d_ancestor - search for an ancestor * @p1: ancestor dentry * @p2: child dentry * * Returns the ancestor dentry of p2 which is a child of p1, if p1 is * an ancestor of p2, else NULL. */ struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) { struct dentry *p; for (p = p2; !IS_ROOT(p); p = p->d_parent) { if (p->d_parent == p1) return p; } return NULL; } /* * This helper attempts to cope with remotely renamed directories * * It assumes that the caller is already holding * dentry->d_parent->d_inode->i_mutex and the dcache_lock * * Note: If ever the locking in lock_rename() changes, then please * remember to update this too... */ static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias) __releases(dcache_lock) { struct mutex *m1 = NULL, *m2 = NULL; struct dentry *ret; /* If alias and dentry share a parent, then no extra locks required */ if (alias->d_parent == dentry->d_parent) goto out_unalias; /* Check for loops */ ret = ERR_PTR(-ELOOP); if (d_ancestor(alias, dentry)) goto out_err; /* See lock_rename() */ ret = ERR_PTR(-EBUSY); if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex)) goto out_err; m1 = &dentry->d_sb->s_vfs_rename_mutex; if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex)) goto out_err; m2 = &alias->d_parent->d_inode->i_mutex; out_unalias: d_move_locked(alias, dentry); ret = alias; out_err: spin_unlock(&dcache_lock); if (m2) mutex_unlock(m2); if (m1) mutex_unlock(m1); return ret; } /* * Prepare an anonymous dentry for life in the superblock's dentry tree as a * named dentry in place of the dentry to be replaced. */ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon) { struct dentry *dparent, *aparent; switch_names(dentry, anon); swap(dentry->d_name.hash, anon->d_name.hash); dparent = dentry->d_parent; aparent = anon->d_parent; dentry->d_parent = (aparent == anon) ? dentry : aparent; list_del(&dentry->d_u.d_child); if (!IS_ROOT(dentry)) list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); else INIT_LIST_HEAD(&dentry->d_u.d_child); anon->d_parent = (dparent == dentry) ? anon : dparent; list_del(&anon->d_u.d_child); if (!IS_ROOT(anon)) list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs); else INIT_LIST_HEAD(&anon->d_u.d_child); anon->d_flags &= ~DCACHE_DISCONNECTED; } /** * d_materialise_unique - introduce an inode into the tree * @dentry: candidate dentry * @inode: inode to bind to the dentry, to which aliases may be attached * * Introduces an dentry into the tree, substituting an extant disconnected * root directory alias in its place if there is one */ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode) { struct dentry *actual; BUG_ON(!d_unhashed(dentry)); spin_lock(&dcache_lock); if (!inode) { actual = dentry; __d_instantiate(dentry, NULL); goto found_lock; } if (S_ISDIR(inode->i_mode)) { struct dentry *alias; /* Does an aliased dentry already exist? */ alias = __d_find_alias(inode, 0); if (alias) { actual = alias; /* Is this an anonymous mountpoint that we could splice * into our tree? */ if (IS_ROOT(alias)) { spin_lock(&alias->d_lock); __d_materialise_dentry(dentry, alias); __d_drop(alias); goto found; } /* Nope, but we must(!) avoid directory aliasing */ actual = __d_unalias(dentry, alias); if (IS_ERR(actual)) dput(alias); goto out_nolock; } } /* Add a unique reference */ actual = __d_instantiate_unique(dentry, inode); if (!actual) actual = dentry; else if (unlikely(!d_unhashed(actual))) goto shouldnt_be_hashed; found_lock: spin_lock(&actual->d_lock); found: _d_rehash(actual); spin_unlock(&actual->d_lock); spin_unlock(&dcache_lock); out_nolock: if (actual == dentry) { security_d_instantiate(dentry, inode); return NULL; } iput(inode); return actual; shouldnt_be_hashed: spin_unlock(&dcache_lock); BUG(); } EXPORT_SYMBOL_GPL(d_materialise_unique); static int prepend(char **buffer, int *buflen, const char *str, int namelen) { *buflen -= namelen; if (*buflen < 0) return -ENAMETOOLONG; *buffer -= namelen; memcpy(*buffer, str, namelen); return 0; } static int prepend_name(char **buffer, int *buflen, struct qstr *name) { return prepend(buffer, buflen, name->name, name->len); } /** * __d_path - return the path of a dentry * @path: the dentry/vfsmount to report * @root: root vfsmnt/dentry (may be modified by this function) * @buffer: buffer to return value in * @buflen: buffer length * * Convert a dentry into an ASCII path name. If the entry has been deleted * the string " (deleted)" is appended. Note that this is ambiguous. * * Returns a pointer into the buffer or an error code if the * path was too long. * * "buflen" should be positive. Caller holds the dcache_lock. * * If path is not reachable from the supplied root, then the value of * root is changed (without modifying refcounts). */ char *__d_path(const struct path *path, struct path *root, char *buffer, int buflen) { struct dentry *dentry = path->dentry; struct vfsmount *vfsmnt = path->mnt; char *end = buffer + buflen; char *retval; spin_lock(&vfsmount_lock); prepend(&end, &buflen, "\0", 1); if (d_unlinked(dentry) && (prepend(&end, &buflen, " (deleted)", 10) != 0)) goto Elong; if (buflen < 1) goto Elong; /* Get '/' right */ retval = end-1; *retval = '/'; for (;;) { struct dentry * parent; if (dentry == root->dentry && vfsmnt == root->mnt) break; if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { /* Global root? */ if (vfsmnt->mnt_parent == vfsmnt) { goto global_root; } dentry = vfsmnt->mnt_mountpoint; vfsmnt = vfsmnt->mnt_parent; continue; } parent = dentry->d_parent; prefetch(parent); if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) || (prepend(&end, &buflen, "/", 1) != 0)) goto Elong; retval = end; dentry = parent; } out: spin_unlock(&vfsmount_lock); return retval; global_root: retval += 1; /* hit the slash */ if (prepend_name(&retval, &buflen, &dentry->d_name) != 0) goto Elong; root->mnt = vfsmnt; root->dentry = dentry; goto out; Elong: retval = ERR_PTR(-ENAMETOOLONG); goto out; } /** * d_path - return the path of a dentry * @path: path to report * @buf: buffer to return value in * @buflen: buffer length * * Convert a dentry into an ASCII path name. If the entry has been deleted * the string " (deleted)" is appended. Note that this is ambiguous. * * Returns a pointer into the buffer or an error code if the path was * too long. Note: Callers should use the returned pointer, not the passed * in buffer, to use the name! The implementation often starts at an offset * into the buffer, and may leave 0 bytes at the start. * * "buflen" should be positive. */ char *d_path(const struct path *path, char *buf, int buflen) { char *res; struct path root; struct path tmp; /* * We have various synthetic filesystems that never get mounted. On * these filesystems dentries are never used for lookup purposes, and * thus don't need to be hashed. They also don't need a name until a * user wants to identify the object in /proc/pid/fd/. The little hack * below allows us to generate a name for these objects on demand: */ if (path->dentry->d_op && path->dentry->d_op->d_dname) return path->dentry->d_op->d_dname(path->dentry, buf, buflen); get_fs_root(current->fs, &root); spin_lock(&dcache_lock); tmp = root; res = __d_path(path, &tmp, buf, buflen); spin_unlock(&dcache_lock); path_put(&root); return res; } EXPORT_SYMBOL(d_path); /* * Helper function for dentry_operations.d_dname() members */ char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, const char *fmt, ...) { va_list args; char temp[64]; int sz; va_start(args, fmt); sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; va_end(args); if (sz > sizeof(temp) || sz > buflen) return ERR_PTR(-ENAMETOOLONG); buffer += buflen - sz; return memcpy(buffer, temp, sz); } /* * Write full pathname from the root of the filesystem into the buffer. */ char *__dentry_path(struct dentry *dentry, char *buf, int buflen) { char *end = buf + buflen; char *retval; prepend(&end, &buflen, "\0", 1); if (buflen < 1) goto Elong; /* Get '/' right */ retval = end-1; *retval = '/'; while (!IS_ROOT(dentry)) { struct dentry *parent = dentry->d_parent; prefetch(parent); if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) || (prepend(&end, &buflen, "/", 1) != 0)) goto Elong; retval = end; dentry = parent; } return retval; Elong: return ERR_PTR(-ENAMETOOLONG); } EXPORT_SYMBOL(__dentry_path); char *dentry_path(struct dentry *dentry, char *buf, int buflen) { char *p = NULL; char *retval; spin_lock(&dcache_lock); if (d_unlinked(dentry)) { p = buf + buflen; if (prepend(&p, &buflen, "//deleted", 10) != 0) goto Elong; buflen++; } retval = __dentry_path(dentry, buf, buflen); spin_unlock(&dcache_lock); if (!IS_ERR(retval) && p) *p = '/'; /* restore '/' overriden with '\0' */ return retval; Elong: spin_unlock(&dcache_lock); return ERR_PTR(-ENAMETOOLONG); } /* * NOTE! The user-level library version returns a * character pointer. The kernel system call just * returns the length of the buffer filled (which * includes the ending '\0' character), or a negative * error value. So libc would do something like * * char *getcwd(char * buf, size_t size) * { * int retval; * * retval = sys_getcwd(buf, size); * if (retval >= 0) * return buf; * errno = -retval; * return NULL; * } */ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) { int error; struct path pwd, root; char *page = (char *) __get_free_page(GFP_USER); if (!page) return -ENOMEM; get_fs_root_and_pwd(current->fs, &root, &pwd); error = -ENOENT; spin_lock(&dcache_lock); if (!d_unlinked(pwd.dentry)) { unsigned long len; struct path tmp = root; char * cwd; cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE); spin_unlock(&dcache_lock); error = PTR_ERR(cwd); if (IS_ERR(cwd)) goto out; error = -ERANGE; len = PAGE_SIZE + page - cwd; if (len <= size) { error = len; if (copy_to_user(buf, cwd, len)) error = -EFAULT; } } else spin_unlock(&dcache_lock); out: path_put(&pwd); path_put(&root); free_page((unsigned long) page); return error; } /* * Test whether new_dentry is a subdirectory of old_dentry. * * Trivially implemented using the dcache structure */ /** * is_subdir - is new dentry a subdirectory of old_dentry * @new_dentry: new dentry * @old_dentry: old dentry * * Returns 1 if new_dentry is a subdirectory of the parent (at any depth). * Returns 0 otherwise. * Caller must ensure that "new_dentry" is pinned before calling is_subdir() */ int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) { int result; unsigned long seq; if (new_dentry == old_dentry) return 1; /* * Need rcu_readlock to protect against the d_parent trashing * due to d_move */ rcu_read_lock(); do { /* for restarting inner loop in case of seq retry */ seq = read_seqbegin(&rename_lock); if (d_ancestor(old_dentry, new_dentry)) result = 1; else result = 0; } while (read_seqretry(&rename_lock, seq)); rcu_read_unlock(); return result; } int path_is_under(struct path *path1, struct path *path2) { struct vfsmount *mnt = path1->mnt; struct dentry *dentry = path1->dentry; int res; spin_lock(&vfsmount_lock); if (mnt != path2->mnt) { for (;;) { if (mnt->mnt_parent == mnt) { spin_unlock(&vfsmount_lock); return 0; } if (mnt->mnt_parent == path2->mnt) break; mnt = mnt->mnt_parent; } dentry = mnt->mnt_mountpoint; } res = is_subdir(dentry, path2->dentry); spin_unlock(&vfsmount_lock); return res; } EXPORT_SYMBOL(path_is_under); void d_genocide(struct dentry *root) { struct dentry *this_parent = root; struct list_head *next; spin_lock(&dcache_lock); repeat: next = this_parent->d_subdirs.next; resume: while (next != &this_parent->d_subdirs) { struct list_head *tmp = next; struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); next = tmp->next; if (d_unhashed(dentry)||!dentry->d_inode) continue; if (!list_empty(&dentry->d_subdirs)) { this_parent = dentry; goto repeat; } atomic_dec(&dentry->d_count); } if (this_parent != root) { next = this_parent->d_u.d_child.next; atomic_dec(&this_parent->d_count); this_parent = this_parent->d_parent; goto resume; } spin_unlock(&dcache_lock); } /** * find_inode_number - check for dentry with name * @dir: directory to check * @name: Name to find. * * Check whether a dentry already exists for the given name, * and return the inode number if it has an inode. Otherwise * 0 is returned. * * This routine is used to post-process directory listings for * filesystems using synthetic inode numbers, and is necessary * to keep getcwd() working. */ ino_t find_inode_number(struct dentry *dir, struct qstr *name) { struct dentry * dentry; ino_t ino = 0; dentry = d_hash_and_lookup(dir, name); if (dentry) { if (dentry->d_inode) ino = dentry->d_inode->i_ino; dput(dentry); } return ino; } EXPORT_SYMBOL(find_inode_number); static __initdata unsigned long dhash_entries; static int __init set_dhash_entries(char *str) { if (!str) return 0; dhash_entries = simple_strtoul(str, &str, 0); return 1; } __setup("dhash_entries=", set_dhash_entries); static void __init dcache_init_early(void) { int loop; /* If hashes are distributed across NUMA nodes, defer * hash allocation until vmalloc space is available. */ if (hashdist) return; dentry_hashtable = alloc_large_system_hash("Dentry cache", sizeof(struct hlist_head), dhash_entries, 13, HASH_EARLY, &d_hash_shift, &d_hash_mask, 0); for (loop = 0; loop < (1 << d_hash_shift); loop++) INIT_HLIST_HEAD(&dentry_hashtable[loop]); } static void __init dcache_init(void) { int loop; /* * A constructor could be added for stable state like the lists, * but it is probably not worth it because of the cache nature * of the dcache. */ dentry_cache = KMEM_CACHE(dentry, SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD); register_shrinker(&dcache_shrinker); /* Hash may have been set up in dcache_init_early */ if (!hashdist) return; dentry_hashtable = alloc_large_system_hash("Dentry cache", sizeof(struct hlist_head), dhash_entries, 13, 0, &d_hash_shift, &d_hash_mask, 0); for (loop = 0; loop < (1 << d_hash_shift); loop++) INIT_HLIST_HEAD(&dentry_hashtable[loop]); } /* SLAB cache for __getname() consumers */ struct kmem_cache *names_cachep __read_mostly; EXPORT_SYMBOL(names_cachep); EXPORT_SYMBOL(d_genocide); void __init vfs_caches_init_early(void) { dcache_init_early(); inode_init_early(); } void __init vfs_caches_init(unsigned long mempages) { unsigned long reserve; /* Base hash sizes on available memory, with a reserve equal to 150% of current kernel size */ reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1); mempages -= reserve; names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); dcache_init(); inode_init(); files_init(mempages); mnt_init(); bdev_cache_init(); chrdev_init(); }