/* * 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 <linux/config.h> #include <linux/syscalls.h> #include <linux/string.h> #include <linux/mm.h> #include <linux/fs.h> #include <linux/fsnotify.h> #include <linux/slab.h> #include <linux/init.h> #include <linux/smp_lock.h> #include <linux/hash.h> #include <linux/cache.h> #include <linux/module.h> #include <linux/mount.h> #include <linux/file.h> #include <asm/uaccess.h> #include <linux/security.h> #include <linux/seqlock.h> #include <linux/swap.h> #include <linux/bootmem.h> int sysctl_vfs_cache_pressure __read_mostly = 100; EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock); static seqlock_t rename_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED; EXPORT_SYMBOL(dcache_lock); static kmem_cache_t *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; static LIST_HEAD(dentry_unused); /* Statistics gathering. */ struct dentry_stat_t dentry_stat = { .age_limit = 45, }; static void d_callback(struct rcu_head *head) { struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu); if (dname_external(dentry)) kfree(dentry->d_name.name); kmem_cache_free(dentry_cache, 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); call_rcu(&dentry->d_u.d_rcu, d_callback); } /* * Release the dentry's inode, using the filesystem * d_iput() operation if defined. * Called with dcache_lock and per dentry lock held, drops both. */ static void dentry_iput(struct dentry * dentry) { 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); } } /* * 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; list_add(&dentry->d_lru, &dentry_unused); dentry_stat.nr_unused++; } spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); return; unhash_it: __d_drop(dentry); kill_it: { struct dentry *parent; /* If dentry was on d_lru list * delete it from there */ if (!list_empty(&dentry->d_lru)) { list_del(&dentry->d_lru); dentry_stat.nr_unused--; } 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); parent = dentry->d_parent; d_free(dentry); if (dentry == parent) return; dentry = parent; goto repeat; } } /** * 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; } /* This should be called _only_ with dcache_lock held */ static inline struct dentry * __dget_locked(struct dentry *dentry) { atomic_inc(&dentry->d_count); if (!list_empty(&dentry->d_lru)) { dentry_stat.nr_unused--; list_del_init(&dentry->d_lru); } return dentry; } struct dentry * dget_locked(struct dentry *dentry) { return __dget_locked(dentry); } /** * 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 a DCACHE_DISCONNECTED alias, then prefer * any other hashed alias over that one unless @want_discon is set, * in which case only return a 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 (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; } /* * 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); } /* * Throw away a dentry - free the inode, dput the parent. This requires that * the LRU list has already been removed. * * Called with dcache_lock, drops it and then regains. * Called with dentry->d_lock held, drops it. */ static void prune_one_dentry(struct dentry * dentry) { struct dentry * parent; __d_drop(dentry); list_del(&dentry->d_u.d_child); dentry_stat.nr_dentry--; /* For d_free, below */ dentry_iput(dentry); parent = dentry->d_parent; d_free(dentry); if (parent != dentry) dput(parent); spin_lock(&dcache_lock); } /** * prune_dcache - shrink the dcache * @count: number of entries to try and free * @sb: if given, ignore dentries for other superblocks * which are being unmounted. * * 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) { spin_lock(&dcache_lock); for (; count ; count--) { struct dentry *dentry; struct list_head *tmp; struct rw_semaphore *s_umount; cond_resched_lock(&dcache_lock); tmp = dentry_unused.prev; if (unlikely(sb)) { /* Try to find a dentry for this sb, but don't try * too hard, if they aren't near the tail they will * be moved down again soon */ int skip = count; while (skip && tmp != &dentry_unused && list_entry(tmp, struct dentry, d_lru)->d_sb != sb) { skip--; tmp = tmp->prev; } } if (tmp == &dentry_unused) break; list_del_init(tmp); prefetch(dentry_unused.prev); dentry_stat.nr_unused--; dentry = list_entry(tmp, struct dentry, d_lru); spin_lock(&dentry->d_lock); /* * We found an inuse dentry which was not removed from * dentry_unused because of laziness during lookup. Do not free * it - just keep it off the dentry_unused list. */ if (atomic_read(&dentry->d_count)) { spin_unlock(&dentry->d_lock); continue; } /* If the dentry was recently referenced, don't free it. */ if (dentry->d_flags & DCACHE_REFERENCED) { dentry->d_flags &= ~DCACHE_REFERENCED; list_add(&dentry->d_lru, &dentry_unused); dentry_stat.nr_unused++; spin_unlock(&dentry->d_lock); continue; } /* * If the dentry is not DCACHED_REFERENCED, it is time * to remove it from the dcache, provided the super block is * NULL (which means we are trying to reclaim memory) * or this dentry belongs to the same super block that * we want to shrink. */ /* * If this dentry is for "my" filesystem, then I can prune it * without taking the s_umount lock (I already hold it). */ if (sb && dentry->d_sb == sb) { prune_one_dentry(dentry); continue; } /* * ...otherwise 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. * (Take a local copy of s_umount to avoid a use-after-free of * `dentry'). */ s_umount = &dentry->d_sb->s_umount; if (down_read_trylock(s_umount)) { if (dentry->d_sb->s_root != NULL) { prune_one_dentry(dentry); up_read(s_umount); continue; } up_read(s_umount); } spin_unlock(&dentry->d_lock); /* Cannot remove the first dentry, and it isn't appropriate * to move it to the head of the list, so give up, and try * later */ break; } spin_unlock(&dcache_lock); } /* * Shrink the dcache for the specified super block. * This allows us to unmount a device without disturbing * the dcache for the other devices. * * This implementation makes just two traversals of the * unused list. On the first pass we move the selected * dentries to the most recent end, and on the second * pass we free them. The second pass must restart after * each dput(), but since the target dentries are all at * the end, it's really just a single traversal. */ /** * 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) { struct list_head *tmp, *next; struct dentry *dentry; /* * Pass one ... move the dentries for the specified * superblock to the most recent end of the unused list. */ spin_lock(&dcache_lock); list_for_each_safe(tmp, next, &dentry_unused) { dentry = list_entry(tmp, struct dentry, d_lru); if (dentry->d_sb != sb) continue; list_del(tmp); list_add(tmp, &dentry_unused); } /* * Pass two ... free the dentries for this superblock. */ repeat: list_for_each_safe(tmp, next, &dentry_unused) { dentry = list_entry(tmp, struct dentry, d_lru); if (dentry->d_sb != sb) continue; dentry_stat.nr_unused--; list_del_init(tmp); spin_lock(&dentry->d_lock); if (atomic_read(&dentry->d_count)) { spin_unlock(&dentry->d_lock); continue; } prune_one_dentry(dentry); cond_resched_lock(&dcache_lock); goto repeat; } spin_unlock(&dcache_lock); } /* * 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; } /* * 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; if (!list_empty(&dentry->d_lru)) { dentry_stat.nr_unused--; list_del_init(&dentry->d_lru); } /* * move only zero ref count dentries to the end * of the unused list for prune_dcache */ if (!atomic_read(&dentry->d_count)) { list_add(&dentry->d_lru, dentry_unused.prev); dentry_stat.nr_unused++; 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) { int found; while ((found = select_parent(parent)) != 0) prune_dcache(found, parent->d_sb); } /** * shrink_dcache_anon - further prune the cache * @head: head of d_hash list of dentries to prune * * Prune the dentries that are anonymous * * parsing d_hash list does not hlist_for_each_entry_rcu() as it * done under dcache_lock. * */ void shrink_dcache_anon(struct super_block *sb) { struct hlist_node *lp; struct hlist_head *head = &sb->s_anon; int found; do { found = 0; spin_lock(&dcache_lock); hlist_for_each(lp, head) { struct dentry *this = hlist_entry(lp, struct dentry, d_hash); if (!list_empty(&this->d_lru)) { dentry_stat.nr_unused--; list_del_init(&this->d_lru); } /* * move only zero ref count dentries to the end * of the unused list for prune_dcache */ if (!atomic_read(&this->d_count)) { list_add_tail(&this->d_lru, &dentry_unused); dentry_stat.nr_unused++; found++; } } spin_unlock(&dcache_lock); prune_dcache(found, sb); } while(found); } /* * 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(int nr, gfp_t gfp_mask) { if (nr) { if (!(gfp_mask & __GFP_FS)) return -1; prune_dcache(nr, NULL); } return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure; } /** * 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; #ifdef CONFIG_PROFILING dentry->d_cookie = NULL; #endif 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; } 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); } /** * 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); if (inode) list_add(&entry->d_alias, &inode->i_dentry); entry->d_inode = inode; fsnotify_d_instantiate(entry, inode); spin_unlock(&dcache_lock); security_d_instantiate(entry, inode); } /** * 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. */ 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; BUG_ON(!list_empty(&entry->d_alias)); spin_lock(&dcache_lock); if (!inode) goto do_negative; 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); spin_unlock(&dcache_lock); BUG_ON(!d_unhashed(alias)); iput(inode); return alias; } list_add(&entry->d_alias, &inode->i_dentry); do_negative: entry->d_inode = inode; fsnotify_d_instantiate(entry, inode); spin_unlock(&dcache_lock); security_d_instantiate(entry, inode); return NULL; } 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; } 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_alloc_anon - allocate an anonymous dentry * @inode: inode to allocate the dentry for * * This is similar to d_alloc_root. It is used by filesystems when * creating a dentry for a given inode, often in the process of * mapping a filehandle to a dentry. The returned dentry may be * anonymous, or may have a full name (if the inode was already * in the cache). The file system may need to make further * efforts to connect this dentry into the dcache properly. * * 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. If %NULL is returned (indicating kmalloc failure), * the reference on the inode has not been released. */ struct dentry * d_alloc_anon(struct inode *inode) { static const struct qstr anonstring = { .name = "" }; struct dentry *tmp; struct dentry *res; if ((res = d_find_alias(inode))) { iput(inode); return res; } tmp = d_alloc(NULL, &anonstring); if (!tmp) return NULL; tmp->d_parent = tmp; /* make sure dput doesn't croak */ spin_lock(&dcache_lock); res = __d_find_alias(inode, 0); if (!res) { /* attach a disconnected dentry */ res = tmp; tmp = NULL; spin_lock(&res->d_lock); res->d_sb = inode->i_sb; res->d_parent = res; res->d_inode = inode; res->d_flags |= DCACHE_DISCONNECTED; res->d_flags &= ~DCACHE_UNHASHED; list_add(&res->d_alias, &inode->i_dentry); hlist_add_head(&res->d_hash, &inode->i_sb->s_anon); spin_unlock(&res->d_lock); inode = NULL; /* don't drop reference */ } spin_unlock(&dcache_lock); if (inode) iput(inode); if (tmp) dput(tmp); return res; } /** * 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) { spin_lock(&dcache_lock); new = __d_find_alias(inode, 1); if (new) { BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); fsnotify_d_instantiate(new, inode); spin_unlock(&dcache_lock); security_d_instantiate(new, inode); d_rehash(dentry); d_move(new, dentry); iput(inode); } else { /* d_instantiate takes dcache_lock, so we do it by hand */ list_add(&dentry->d_alias, &inode->i_dentry); dentry->d_inode = inode; fsnotify_d_instantiate(dentry, inode); spin_unlock(&dcache_lock); security_d_instantiate(dentry, inode); d_rehash(dentry); } } else d_add(dentry, inode); return new; } /** * 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 d_put 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. * * dentry_unused list 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; } 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; /* * 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; } if (!d_unhashed(dentry)) { 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) * @hash: Hash of the dentry * @len: Length of the name * * 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; } /* * 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_iput(dentry); fsnotify_nameremove(dentry, isdir); /* remove this and other inotify debug checks after 2.6.18 */ dentry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED; return; } if (!d_unhashed(dentry)) __d_drop(dentry); spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); fsnotify_nameremove(dentry, isdir); } static void __d_rehash(struct dentry * entry, struct hlist_head *list) { entry->d_flags &= ~DCACHE_UNHASHED; hlist_add_head_rcu(&entry->d_hash, list); } /** * 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) { struct hlist_head *list = d_hash(entry->d_parent, entry->d_name.hash); spin_lock(&dcache_lock); spin_lock(&entry->d_lock); __d_rehash(entry, list); spin_unlock(&entry->d_lock); spin_unlock(&dcache_lock); } #define do_switch(x,y) do { \ __typeof__ (x) __tmp = x; \ x = y; y = __tmp; } while (0) /* * 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 */ do_switch(target->d_name.name, dentry->d_name.name); } else { /* * dentry:internal, target:external. Steal target's * storage and make target internal. */ 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); } } } /* * 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 got deleted rather than the name that * deleted it. */ /** * 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) { struct hlist_head *list; if (!dentry->d_inode) printk(KERN_WARNING "VFS: moving negative dcache entry\n"); spin_lock(&dcache_lock); write_seqlock(&rename_lock); /* * XXXX: do we really need to take target->d_lock? */ if (target < dentry) { spin_lock(&target->d_lock); spin_lock(&dentry->d_lock); } else { spin_lock(&dentry->d_lock); spin_lock(&target->d_lock); } /* Move the dentry to the target hash queue, if on different bucket */ if (dentry->d_flags & DCACHE_UNHASHED) 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); do_switch(dentry->d_name.len, target->d_name.len); do_switch(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 { do_switch(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); spin_unlock(&dcache_lock); } /** * d_path - return the path of a dentry * @dentry: dentry to report * @vfsmnt: vfsmnt to which the dentry belongs * @root: root dentry * @rootmnt: vfsmnt to which the root dentry belongs * @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 the buffer or an error code if the path was too long. * * "buflen" should be positive. Caller holds the dcache_lock. */ static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt, struct dentry *root, struct vfsmount *rootmnt, char *buffer, int buflen) { char * end = buffer+buflen; char * retval; int namelen; *--end = '\0'; buflen--; if (!IS_ROOT(dentry) && d_unhashed(dentry)) { buflen -= 10; end -= 10; if (buflen < 0) goto Elong; memcpy(end, " (deleted)", 10); } if (buflen < 1) goto Elong; /* Get '/' right */ retval = end-1; *retval = '/'; for (;;) { struct dentry * parent; if (dentry == root && vfsmnt == rootmnt) break; if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { /* Global root? */ spin_lock(&vfsmount_lock); if (vfsmnt->mnt_parent == vfsmnt) { spin_unlock(&vfsmount_lock); goto global_root; } dentry = vfsmnt->mnt_mountpoint; vfsmnt = vfsmnt->mnt_parent; spin_unlock(&vfsmount_lock); continue; } parent = dentry->d_parent; prefetch(parent); namelen = dentry->d_name.len; buflen -= namelen + 1; if (buflen < 0) goto Elong; end -= namelen; memcpy(end, dentry->d_name.name, namelen); *--end = '/'; retval = end; dentry = parent; } return retval; global_root: namelen = dentry->d_name.len; buflen -= namelen; if (buflen < 0) goto Elong; retval -= namelen-1; /* hit the slash */ memcpy(retval, dentry->d_name.name, namelen); return retval; Elong: return ERR_PTR(-ENAMETOOLONG); } /* write full pathname into buffer and return start of pathname */ char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt, char *buf, int buflen) { char *res; struct vfsmount *rootmnt; struct dentry *root; read_lock(¤t->fs->lock); rootmnt = mntget(current->fs->rootmnt); root = dget(current->fs->root); read_unlock(¤t->fs->lock); spin_lock(&dcache_lock); res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen); spin_unlock(&dcache_lock); dput(root); mntput(rootmnt); return res; } /* * 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; * } */ asmlinkage long sys_getcwd(char __user *buf, unsigned long size) { int error; struct vfsmount *pwdmnt, *rootmnt; struct dentry *pwd, *root; char *page = (char *) __get_free_page(GFP_USER); if (!page) return -ENOMEM; read_lock(¤t->fs->lock); pwdmnt = mntget(current->fs->pwdmnt); pwd = dget(current->fs->pwd); rootmnt = mntget(current->fs->rootmnt); root = dget(current->fs->root); read_unlock(¤t->fs->lock); error = -ENOENT; /* Has the current directory has been unlinked? */ spin_lock(&dcache_lock); if (pwd->d_parent == pwd || !d_unhashed(pwd)) { unsigned long len; char * cwd; cwd = __d_path(pwd, pwdmnt, root, rootmnt, 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: dput(pwd); mntput(pwdmnt); dput(root); mntput(rootmnt); 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; struct dentry * saved = new_dentry; unsigned long seq; /* 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 */ new_dentry = saved; result = 0; seq = read_seqbegin(&rename_lock); for (;;) { if (new_dentry != old_dentry) { struct dentry * parent = new_dentry->d_parent; if (parent == new_dentry) break; new_dentry = parent; continue; } result = 1; break; } } while (read_seqretry(&rename_lock, seq)); rcu_read_unlock(); return result; } 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; } 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(unsigned long mempages) { 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_create("dentry_cache", sizeof(struct dentry), 0, (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| SLAB_MEM_SPREAD), NULL, NULL); set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory); /* 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 */ kmem_cache_t *names_cachep __read_mostly; /* SLAB cache for file structures */ kmem_cache_t *filp_cachep __read_mostly; EXPORT_SYMBOL(d_genocide); extern void bdev_cache_init(void); extern void chrdev_init(void); 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, NULL); filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); dcache_init(mempages); inode_init(mempages); files_init(mempages); mnt_init(mempages); bdev_cache_init(); chrdev_init(); } EXPORT_SYMBOL(d_alloc); EXPORT_SYMBOL(d_alloc_anon); EXPORT_SYMBOL(d_alloc_root); EXPORT_SYMBOL(d_delete); EXPORT_SYMBOL(d_find_alias); EXPORT_SYMBOL(d_instantiate); EXPORT_SYMBOL(d_invalidate); EXPORT_SYMBOL(d_lookup); EXPORT_SYMBOL(d_move); EXPORT_SYMBOL(d_path); EXPORT_SYMBOL(d_prune_aliases); EXPORT_SYMBOL(d_rehash); EXPORT_SYMBOL(d_splice_alias); EXPORT_SYMBOL(d_validate); EXPORT_SYMBOL(dget_locked); EXPORT_SYMBOL(dput); EXPORT_SYMBOL(find_inode_number); EXPORT_SYMBOL(have_submounts); EXPORT_SYMBOL(names_cachep); EXPORT_SYMBOL(shrink_dcache_parent); EXPORT_SYMBOL(shrink_dcache_sb);