dm snapshot: fix lockup in dm_exception_table_exit

There was reported lockup when we exit a snapshot with many exceptions.
Fix this by adding "cond_resched" to the loop that frees the exceptions.

Reported-by: John Pittman <jpittman@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index bf7a574..0ace06d 100644 (file)
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -684,8 +684,10 @@ static void dm_exception_table_exit(struct dm_exception_table *et,
        for (i = 0; i < size; i++) {
                slot = et->table + i;
 
-               hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list)
+               hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list) {
                        kmem_cache_free(mem, ex);
+                       cond_resched();
+               }
        }
 
        kvfree(et->table);