fix get_active_super()/umount() race

This one needs restarts...

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

1 files changed, 7 insertions, 7 deletions

diff --git a/fs/super.c b/fs/super.c
index 4df8233dfb61..44971d7df1ce 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -471,17 +471,17 @@ struct super_block *get_active_super(struct block_device *bdev)
         if (!bdev)
                 return NULL;
 
+restart:
         spin_lock(&sb_lock);
         list_for_each_entry(sb, &super_blocks, s_list) {
                 if (list_empty(&sb->s_instances))
                         continue;
-                if (sb->s_bdev != bdev)
-                        continue;
-
-                if (grab_super(sb)) /* drops sb_lock */
-                        return sb;
-
-                spin_lock(&sb_lock);
+                if (sb->s_bdev == bdev) {
+                        if (grab_super(sb)) /* drops sb_lock */
+                                return sb;
+                        else
+                                goto restart;
+                }
         }
         spin_unlock(&sb_lock);
         return NULL;