-/*
- * 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);
- }
-}
-