[GFS2] Fix recursive locking in gfs2_permission

Since gfs2_permission may be called either from the VFS (in which case
we need to obtain a shared glock) or from GFS2 (in which case we already
have a glock) we need to test to see whether or not a lock is required.
The original test was buggy due to a potential race. This one should
be safe.

This fixes Red Hat bugzilla #217129

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 13 insertions, 6 deletions

diff --git a/fs/gfs2/ops_inode.c b/fs/gfs2/ops_inode.c
index b247f25effbf..fd9fee2ceeac 100644
--- a/fs/gfs2/ops_inode.c
+++ b/fs/gfs2/ops_inode.c
@@ -835,6 +835,10 @@ static void *gfs2_follow_link(struct dentry *dentry, struct nameidata *nd)
  * @mask:
  * @nd: passed from Linux VFS, ignored by us
  *
+ * This may be called from the VFS directly, or from within GFS2 with the
+ * inode locked, so we look to see if the glock is already locked and only
+ * lock the glock if its not already been done.
+ *
  * Returns: errno
  */
 
@@ -843,15 +847,18 @@ static int gfs2_permission(struct inode *inode, int mask, struct nameidata *nd)
         struct gfs2_inode *ip = GFS2_I(inode);
         struct gfs2_holder i_gh;
         int error;
+        int unlock = 0;
 
-        if (!test_bit(GIF_INVALID, &ip->i_flags))
-                return generic_permission(inode, mask, gfs2_check_acl);
+        if (gfs2_glock_is_locked_by_me(ip->i_gl) == 0) {
+                error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
+                if (error)
+                        return error;
+                unlock = 1;
+        }
 
-        error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
-        if (!error) {
-                error = generic_permission(inode, mask, gfs2_check_acl_locked);
+        error = generic_permission(inode, mask, gfs2_check_acl_locked);
+        if (unlock)
                 gfs2_glock_dq_uninit(&i_gh);
-        }
 
         return error;
 }