dm cache: fix leaking of deferred bio prison cells

commit 9153df7405ae04c1b0466de720e0a685cfea1a3a upstream.

There were two cases where dm_cell_visit_release() was being called,
which removes the cell from the prison's rbtree, but the callers didn't
also return the cell to the mempool.  Fix this by having them call
free_prison_cell().

This leak manifested as the 'kmalloc-96' slab growing until OOM.

Fixes: 651f5fa2a3 ("dm cache: defer whole cells")
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 1fe93cfea7d309a659d79fe2b953b5f2dbe7b466..9d0672b58c3110dc44664dd1c8efbf1c17be646a 100644 (file)
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -1729,6 +1729,8 @@ static void remap_cell_to_origin_clear_discard(struct cache *cache,
                remap_to_origin(cache, bio);
                issue(cache, bio);
        }
+
+       free_prison_cell(cache, cell);
 }
 
 static void remap_cell_to_cache_dirty(struct cache *cache, struct dm_bio_prison_cell *cell,
@@ -1763,6 +1765,8 @@ static void remap_cell_to_cache_dirty(struct cache *cache, struct dm_bio_prison_
                remap_to_cache(cache, bio, cblock);
                issue(cache, bio);
        }
+
+       free_prison_cell(cache, cell);
 }
 
 /*----------------------------------------------------------------*/