X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Fdcache.c;h=0e73aa0a0e8b66a1bf213ed53ad579bbabe7b2f3;hb=b9b712765738d141154b435a5bfec4adbbee25f3;hp=fc2faa44f8d185b6be9b8600a4ffb9991d5b980f;hpb=07f3f05c1e3052b8656129b2a5aca9f888241a34;p=safe%2Fjmp%2Flinux-2.6 diff --git a/fs/dcache.c b/fs/dcache.c index fc2faa4..0e73aa0 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -21,7 +21,6 @@ #include #include #include -#include #include #include #include @@ -43,7 +42,7 @@ static __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); EXPORT_SYMBOL(dcache_lock); -static kmem_cache_t *dentry_cache __read_mostly; +static struct kmem_cache *dentry_cache __read_mostly; #define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname)) @@ -68,15 +67,19 @@ struct dentry_stat_t dentry_stat = { .age_limit = 45, }; -static void d_callback(struct rcu_head *head) +static void __d_free(struct dentry *dentry) { - 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); } +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. @@ -85,7 +88,11 @@ 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); + /* if dentry was never inserted into hash, immediate free is OK */ + if (dentry->d_hash.pprev == NULL) + __d_free(dentry); + else + call_rcu(&dentry->d_u.d_rcu, d_callback); } /* @@ -113,6 +120,28 @@ static void dentry_iput(struct dentry * dentry) } } +/** + * d_kill - kill dentry and return parent + * @dentry: dentry to kill + * + * Called with dcache_lock and d_lock, releases both. 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) +{ + 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); + parent = dentry->d_parent; + d_free(dentry); + return dentry == parent ? NULL : parent; +} + /* * This is dput * @@ -181,28 +210,17 @@ repeat: 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; +kill_it: + /* 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--; } + dentry = d_kill(dentry); + if (dentry) + goto repeat; } /** @@ -291,9 +309,9 @@ struct dentry * dget_locked(struct dentry *dentry) * 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 + * 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 a DCACHE_DISCONNECTED alias. + * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias. */ static struct dentry * __d_find_alias(struct inode *inode, int want_discon) @@ -309,7 +327,8 @@ static struct dentry * __d_find_alias(struct inode *inode, int want_discon) 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) + if (IS_ROOT(alias) && + (alias->d_flags & DCACHE_DISCONNECTED)) discon_alias = alias; else if (!want_discon) { __dget_locked(alias); @@ -362,22 +381,40 @@ restart: * Throw away a dentry - free the inode, dput the parent. This requires that * the LRU list has already been removed. * + * If prune_parents is true, try to prune ancestors as well. + * * 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) +static void prune_one_dentry(struct dentry * dentry, int prune_parents) { - 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); + dentry = d_kill(dentry); + if (!prune_parents) { + dput(dentry); + spin_lock(&dcache_lock); + return; + } + + /* + * 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); + if (!list_empty(&dentry->d_lru)) { + list_del(&dentry->d_lru); + dentry_stat.nr_unused--; + } + __d_drop(dentry); + dentry = d_kill(dentry); + spin_lock(&dcache_lock); + } } /** @@ -385,6 +422,7 @@ static void prune_one_dentry(struct dentry * dentry) * @count: number of entries to try and free * @sb: if given, ignore dentries for other superblocks * which are being unmounted. + * @prune_parents: if true, try to prune ancestors as well in one go * * Shrink the dcache. This is done when we need * more memory, or simply when we need to unmount @@ -395,7 +433,7 @@ static void prune_one_dentry(struct dentry * dentry) * all the dentries are in use. */ -static void prune_dcache(int count, struct super_block *sb) +static void prune_dcache(int count, struct super_block *sb, int prune_parents) { spin_lock(&dcache_lock); for (; count ; count--) { @@ -455,7 +493,7 @@ static void prune_dcache(int count, struct super_block *sb) * without taking the s_umount lock (I already hold it). */ if (sb && dentry->d_sb == sb) { - prune_one_dentry(dentry); + prune_one_dentry(dentry, prune_parents); continue; } /* @@ -470,18 +508,19 @@ static void prune_dcache(int count, struct super_block *sb) s_umount = &dentry->d_sb->s_umount; if (down_read_trylock(s_umount)) { if (dentry->d_sb->s_root != NULL) { - prune_one_dentry(dentry); + prune_one_dentry(dentry, prune_parents); 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 + /* + * Insert dentry at the head of the list as inserting at the + * tail leads to a cycle. */ - break; + list_add(&dentry->d_lru, &dentry_unused); + dentry_stat.nr_unused++; } spin_unlock(&dcache_lock); } @@ -540,7 +579,7 @@ repeat: spin_unlock(&dentry->d_lock); continue; } - prune_one_dentry(dentry); + prune_one_dentry(dentry, 1); cond_resched_lock(&dcache_lock); goto repeat; } @@ -548,6 +587,142 @@ repeat: } /* + * 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); + if (!list_empty(&dentry->d_lru)) { + dentry_stat.nr_unused--; + list_del_init(&dentry->d_lru); + } + __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) { + if (!list_empty(&loop->d_lru)) { + dentry_stat.nr_unused--; + list_del_init(&loop->d_lru); + } + + __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(); + } + + parent = dentry->d_parent; + if (parent == dentry) + parent = NULL; + else + 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. @@ -683,7 +858,7 @@ void shrink_dcache_parent(struct dentry * parent) int found; while ((found = select_parent(parent)) != 0) - prune_dcache(found, parent->d_sb); + prune_dcache(found, parent->d_sb, 1); } /* @@ -703,7 +878,7 @@ static int shrink_dcache_memory(int nr, gfp_t gfp_mask) if (nr) { if (!(gfp_mask & __GFP_FS)) return -1; - prune_dcache(nr, NULL); + prune_dcache(nr, NULL, 1); } return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure; } @@ -1004,7 +1179,7 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) { struct dentry *new = NULL; - if (inode) { + if (inode && S_ISDIR(inode->i_mode)) { spin_lock(&dcache_lock); new = __d_find_alias(inode, 1); if (new) { @@ -1338,23 +1513,21 @@ static void switch_names(struct dentry *dentry, struct dentry *target) * deleted it. */ -/** - * d_move - move a dentry +/* + * 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. */ - -void d_move(struct dentry * dentry, struct dentry * target) +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"); - spin_lock(&dcache_lock); write_seqlock(&rename_lock); /* * XXXX: do we really need to take target->d_lock? @@ -1405,7 +1578,81 @@ already_unhashed: 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); +} + +/* + * Helper that returns 1 if p1 is a parent of p2, else 0 + */ +static int d_isparent(struct dentry *p1, struct dentry *p2) +{ + struct dentry *p; + + for (p = p2; p->d_parent != p; p = p->d_parent) { + if (p->d_parent == p1) + return 1; + } + return 0; +} + +/* + * 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... + * + * On return, dcache_lock will have been unlocked. + */ +static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias) +{ + 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_isparent(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; } /* @@ -1450,7 +1697,7 @@ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon) */ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode) { - struct dentry *alias, *actual; + struct dentry *actual; BUG_ON(!d_unhashed(dentry)); @@ -1462,26 +1709,27 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode) goto found_lock; } - /* See if a disconnected directory already exists as an anonymous root - * that we should splice into the tree instead */ - if (S_ISDIR(inode->i_mode) && (alias = __d_find_alias(inode, 1))) { - spin_lock(&alias->d_lock); - - /* Is this a mountpoint that we could splice into our tree? */ - if (IS_ROOT(alias)) - goto connect_mountpoint; - - if (alias->d_name.len == dentry->d_name.len && - alias->d_parent == dentry->d_parent && - memcmp(alias->d_name.name, - dentry->d_name.name, - dentry->d_name.len) == 0) - goto replace_with_alias; - - spin_unlock(&alias->d_lock); - - /* Doh! Seem to be aliasing directories for some reason... */ - dput(alias); + 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 */ @@ -1497,7 +1745,7 @@ 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; @@ -1506,16 +1754,6 @@ found: iput(inode); return actual; - /* Convert the anonymous/root alias into an ordinary dentry */ -connect_mountpoint: - __d_materialise_dentry(dentry, alias); - - /* Replace the candidate dentry with the alias in the tree */ -replace_with_alias: - __d_drop(alias); - actual = alias; - goto found; - shouldnt_be_hashed: spin_unlock(&dcache_lock); BUG(); @@ -1614,6 +1852,16 @@ char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt, struct vfsmount *rootmnt; struct dentry *root; + /* + * 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 (dentry->d_op && dentry->d_op->d_dname) + return dentry->d_op->d_dname(dentry, buf, buflen); + read_lock(¤t->fs->lock); rootmnt = mntget(current->fs->rootmnt); root = dget(current->fs->root); @@ -1627,6 +1875,27 @@ char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt, } /* + * 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); +} + +/* * NOTE! The user-level library version returns a * character pointer. The kernel system call just * returns the length of the buffer filled (which @@ -1843,12 +2112,8 @@ static void __init dcache_init(unsigned long mempages) * 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); + dentry_cache = KMEM_CACHE(dentry, + SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD); set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory); @@ -1871,10 +2136,10 @@ static void __init dcache_init(unsigned long mempages) } /* SLAB cache for __getname() consumers */ -kmem_cache_t *names_cachep __read_mostly; +struct kmem_cache *names_cachep __read_mostly; /* SLAB cache for file structures */ -kmem_cache_t *filp_cachep __read_mostly; +struct kmem_cache *filp_cachep __read_mostly; EXPORT_SYMBOL(d_genocide);