diff options
Diffstat (limited to 'fs/dcache.c')
| -rw-r--r-- | fs/dcache.c | 1764 |
1 files changed, 1764 insertions, 0 deletions
diff --git a/fs/dcache.c b/fs/dcache.c new file mode 100644 index 0000000..496a4e0 --- /dev/null +++ b/fs/dcache.c @@ -0,0 +1,1764 @@ +/* + * 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/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> + +/* #define DCACHE_DEBUG 1 */ + +int sysctl_vfs_cache_pressure = 100; +EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); + + __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock); +seqlock_t rename_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED; + +EXPORT_SYMBOL(dcache_lock); + +static kmem_cache_t *dentry_cache; + +#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; +static unsigned int d_hash_shift; +static struct hlist_head *dentry_hashtable; +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_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_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 inline 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 (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_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; + 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 list_head *tmp, *head = &inode->i_dentry; +restart: + spin_lock(&dcache_lock); + tmp = head; + while ((tmp = tmp->next) != head) { + struct dentry *dentry = list_entry(tmp, struct 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. + */ +static inline void prune_one_dentry(struct dentry * dentry) +{ + struct dentry * parent; + + __d_drop(dentry); + list_del(&dentry->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 + * + * 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) +{ + spin_lock(&dcache_lock); + for (; count ; count--) { + struct dentry *dentry; + struct list_head *tmp; + + cond_resched_lock(&dcache_lock); + + tmp = dentry_unused.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; + } + prune_one_dentry(dentry); + } + 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); + next = dentry_unused.next; + while (next != &dentry_unused) { + tmp = next; + next = tmp->next; + 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: + next = dentry_unused.next; + while (next != &dentry_unused) { + tmp = next; + next = tmp->next; + 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); + 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_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_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_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; +#ifdef DCACHE_DEBUG +printk(KERN_DEBUG "select_parent: descending to %s/%s, found=%d\n", +dentry->d_parent->d_name.name, dentry->d_name.name, found); +#endif + goto repeat; + } + } + /* + * All done at this level ... ascend and resume the search. + */ + if (this_parent != parent) { + next = this_parent->d_child.next; + this_parent = this_parent->d_parent; +#ifdef DCACHE_DEBUG +printk(KERN_DEBUG "select_parent: ascending to %s/%s, found=%d\n", +this_parent->d_parent->d_name.name, this_parent->d_name.name, found); +#endif + 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); +} + +/** + * 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_rcu() as it + * done under dcache_lock. + * + */ +void shrink_dcache_anon(struct hlist_head *head) +{ + struct hlist_node *lp; + 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); + } 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, unsigned int gfp_mask) +{ + if (nr) { + if (!(gfp_mask & __GFP_FS)) + return -1; + prune_dcache(nr); + } + 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; + dentry->d_cookie = NULL; + 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_child); + } + + spin_lock(&dcache_lock); + if (parent) + list_add(&dentry->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) +{ + if (!list_empty(&entry->d_alias)) BUG(); + spin_lock(&dcache_lock); + if (inode) + list_add(&entry->d_alias, &inode->i_dentry); + entry->d_inode = 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. + * + * Note that in order to avoid conflicts with rename() etc, the caller + * had better be holding the parent directory semaphore. + */ +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)); + return alias; + } + list_add(&entry->d_alias, &inode->i_dentry); +do_negative: + entry->d_inode = 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)); + 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; + 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; + + rcu_read_lock(); + + hlist_for_each_rcu(node, head) { + struct dentry *dentry; + struct qstr *qstr; + + dentry = hlist_entry(node, struct dentry, d_hash); + + 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_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_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) +{ + /* + * Are we the only user? + */ + spin_lock(&dcache_lock); + spin_lock(&dentry->d_lock); + if (atomic_read(&dentry->d_count) == 1) { + dentry_iput(dentry); + return; + } + + if (!d_unhashed(dentry)) + __d_drop(dentry); + + spin_unlock(&dentry->d_lock); + spin_unlock(&dcache_lock); +} + +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_child); + list_del(&target->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_child); + } else { + do_switch(dentry->d_parent, target->d_parent); + + /* And add them back to the (new) parent lists */ + list_add(&target->d_child, &target->d_parent->d_subdirs); + } + + list_add(&dentry->d_child, &dentry->d_parent->d_subdirs); + spin_unlock(&target->d_lock); + 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_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_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; + + /* + * 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); + if (dentry) + { + if (dentry->d_inode) + ino = dentry->d_inode->i_ino; + dput(dentry); + } +out: + 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, + 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; + +/* SLAB cache for file structures */ +kmem_cache_t *filp_cachep; + +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, filp_ctor, filp_dtor); + + 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); |
