kernfs: fix a subdir count leak

Currently kernfs_link_sibling() increates parent->dir.subdirs before
adding the node into parent's chidren rb tree.

Because it is possible that kernfs_link_sibling() couldn't find
a suitable slot and bail out, this leads to a mismatch between
elevated subdir count with actual children node numbers.

This patches fix this problem, by moving the subdir accouting
after the actual addtion happening.

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 78f3403300af..ac127cd008bf 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -232,9 +232,6 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
         struct rb_node **node = &kn->parent->dir.children.rb_node;
         struct rb_node *parent = NULL;
 
-        if (kernfs_type(kn) == KERNFS_DIR)
-                kn->parent->dir.subdirs++;
-
         while (*node) {
                 struct kernfs_node *pos;
                 int result;
@@ -249,9 +246,15 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
                 else
                         return -EEXIST;
         }
+
         /* add new node and rebalance the tree */
         rb_link_node(&kn->rb, parent, node);
         rb_insert_color(&kn->rb, &kn->parent->dir.children);
+
+        /* successfully added, account subdir number */
+        if (kernfs_type(kn) == KERNFS_DIR)
+                kn->parent->dir.subdirs++;
+
         return 0;
 }