switch shrink_dcache_for_umount() to use of d_walk()

we have too many iterators in fs/dcache.c...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/dcache.c b/fs/dcache.c
index c8e83d0..eb0978d 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1075,116 +1075,6 @@ void shrink_dcache_sb(struct super_block *sb)
 EXPORT_SYMBOL(shrink_dcache_sb);
 
 /*
- * 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));
-
-       for (;;) {
-               /* descend to the first leaf in the current subtree */
-               while (!list_empty(&dentry->d_subdirs))
-                       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;
-
-                       /*
-                        * inform the fs that this dentry is about to be
-                        * unhashed and destroyed.
-                        */
-                       if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
-                           !d_unhashed(dentry))
-                               dentry->d_op->d_prune(dentry);
-
-                       dentry_lru_del(dentry);
-                       __d_shrink(dentry);
-
-                       if (dentry->d_lockref.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,
-                                      dentry->d_lockref.count,
-                                      dentry->d_sb->s_type->name,
-                                      dentry->d_sb->s_id);
-                               BUG();
-                       }
-
-                       if (IS_ROOT(dentry)) {
-                               parent = NULL;
-                               list_del(&dentry->d_u.d_child);
-                       } else {
-                               parent = dentry->d_parent;
-                               parent->d_lockref.count--;
-                               list_del(&dentry->d_u.d_child);
-                       }
-
-                       inode = dentry->d_inode;
-                       if (inode) {
-                               dentry->d_inode = NULL;
-                               hlist_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 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;
-       dentry->d_lockref.count--;
-       shrink_dcache_for_umount_subtree(dentry);
-
-       while (!hlist_bl_empty(&sb->s_anon)) {
-               dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
-               shrink_dcache_for_umount_subtree(dentry);
-       }
-}
-
-/*
  * This tries to ascend one level of parenthood, but
  * we can race with renaming, so we need to re-check
  * the parenthood after dropping the lock and check
@@ -1478,6 +1368,91 @@ void shrink_dcache_parent(struct dentry *parent)
 }
 EXPORT_SYMBOL(shrink_dcache_parent);
 
+static enum d_walk_ret umount_collect(void *_data, struct dentry *dentry)
+{
+       struct select_data *data = _data;
+       enum d_walk_ret ret = D_WALK_CONTINUE;
+
+       if (dentry->d_lockref.count) {
+               dentry_lru_del(dentry);
+               if (likely(!list_empty(&dentry->d_subdirs)))
+                       goto out;
+               if (dentry == data->start && dentry->d_lockref.count == 1)
+                       goto out;
+               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,
+                      dentry->d_lockref.count,
+                      dentry->d_sb->s_type->name,
+                      dentry->d_sb->s_id);
+               BUG();
+       } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
+               /*
+                * We can't use d_lru_shrink_move() because we
+                * need to get the global LRU lock and do the
+                * LRU accounting.
+                */
+               if (dentry->d_flags & DCACHE_LRU_LIST)
+                       d_lru_del(dentry);
+               d_shrink_add(dentry, &data->dispose);
+               data->found++;
+               ret = D_WALK_NORETRY;
+       }
+out:
+       if (data->found && need_resched())
+               ret = D_WALK_QUIT;
+       return ret;
+}
+
+/*
+ * destroy the dentries attached to a superblock on unmounting
+ */
+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;
+       for (;;) {
+               struct select_data data;
+
+               INIT_LIST_HEAD(&data.dispose);
+               data.start = dentry;
+               data.found = 0;
+
+               d_walk(dentry, &data, umount_collect, NULL);
+               if (!data.found)
+                       break;
+
+               shrink_dentry_list(&data.dispose);
+               cond_resched();
+       }
+       d_drop(dentry);
+       dput(dentry);
+
+       while (!hlist_bl_empty(&sb->s_anon)) {
+               struct select_data data;
+               dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
+
+               INIT_LIST_HEAD(&data.dispose);
+               data.start = NULL;
+               data.found = 0;
+
+               d_walk(dentry, &data, umount_collect, NULL);
+               if (data.found)
+                       shrink_dentry_list(&data.dispose);
+               cond_resched();
+       }
+}
+
 static enum d_walk_ret check_and_collect(void *_data, struct dentry *dentry)
 {
        struct select_data *data = _data;