[PATCH] VFS: Fix an error in unused dentry counting

With Vasily Averin <vvs@sw.ru>

Fix an error in unused dentry counting in shrink_dcache_for_umount_subtree()
in which the count is modified without the dcache_lock held.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Vasily Averin <vvs@sw.ru>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index a5b76b647c6d..fd4a428998ef 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -557,6 +557,7 @@ repeat:
 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 {
         struct dentry *parent;
+        unsigned detached = 0;
 
         BUG_ON(!IS_ROOT(dentry));
 
@@ -621,7 +622,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
                                 atomic_dec(&parent->d_count);
 
                         list_del(&dentry->d_u.d_child);
-                        dentry_stat.nr_dentry--;        /* For d_free, below */
+                        detached++;
 
                         inode = dentry->d_inode;
                         if (inode) {
@@ -639,7 +640,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
                          * otherwise we ascend to the parent and move to the
                          * next sibling if there is one */
                         if (!parent)
-                                return;
+                                goto out;
 
                         dentry = parent;
 
@@ -648,6 +649,11 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
                 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);
 }
 
 /*