vfs: Fix invalid ida_remove() call

When the group id of a shared mount is not allocated, the umount still
tries to call mnt_release_group_id(), which eventually hits a kernel
warning at ida_remove() spewing a message like:
  ida_remove called for id=0 which is not allocated.

This patch fixes the bug simply checking the group id in the caller.

Reported-by: Cristian Rodríguez <crrodriguez@opensuse.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/pnode.c b/fs/pnode.c
index 3d2a7141b87a..9af0df15256e 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -83,7 +83,8 @@ static int do_make_slave(struct mount *mnt)
                 if (peer_mnt == mnt)
                         peer_mnt = NULL;
         }
-        if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share))
+        if (mnt->mnt_group_id && IS_MNT_SHARED(mnt) &&
+            list_empty(&mnt->mnt_share))
                 mnt_release_group_id(mnt);
 
         list_del_init(&mnt->mnt_share);