[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>

diff --git a/fs/dcache.c b/fs/dcache.c
index a5b76b6..fd4a428 100644 (file)
--- 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);
 }
 
 /*