diff options
| -rw-r--r-- | fs/dcache.c | 130 | ||||
| -rw-r--r-- | fs/super.c | 12 | ||||
| -rw-r--r-- | include/linux/dcache.h | 1 |
3 files changed, 137 insertions, 6 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 2355bddad8de..2bac4ba1d1d3 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -549,6 +549,136 @@ 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; + + 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); + dentry_stat.nr_dentry--; /* For d_free, below */ + + 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) + return; + + dentry = parent; + + } while (list_empty(&dentry->d_subdirs)); + + dentry = list_entry(dentry->d_subdirs.next, + struct dentry, d_u.d_child); + } +} + +/* + * 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. diff --git a/fs/super.c b/fs/super.c index aec99ddbe53f..47e554c12e76 100644 --- a/fs/super.c +++ b/fs/super.c @@ -260,17 +260,17 @@ int fsync_super(struct super_block *sb) * that need destruction out of superblock, call generic_shutdown_super() * and release aforementioned objects. Note: dentries and inodes _are_ * taken care of and do not need specific handling. + * + * Upon calling this function, the filesystem may no longer alter or + * rearrange the set of dentries belonging to this super_block, nor may it + * change the attachments of dentries to inodes. */ void generic_shutdown_super(struct super_block *sb) { - struct dentry *root = sb->s_root; struct super_operations *sop = sb->s_op; - if (root) { - sb->s_root = NULL; - shrink_dcache_parent(root); - shrink_dcache_sb(sb); - dput(root); + if (sb->s_root) { + shrink_dcache_for_umount(sb); fsync_super(sb); lock_super(sb); sb->s_flags &= ~MS_ACTIVE; diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 44605be59409..63f64a9a5bf7 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -230,6 +230,7 @@ extern struct dentry * d_alloc_anon(struct inode *); extern struct dentry * d_splice_alias(struct inode *, struct dentry *); extern void shrink_dcache_sb(struct super_block *); extern void shrink_dcache_parent(struct dentry *); +extern void shrink_dcache_for_umount(struct super_block *); extern int d_invalidate(struct dentry *); /* only used at mount-time */ |