[PATCH 4.2 115/120] dm cache: fix leaking of deferred bio prison cells

Greg Kroah-Hartman
2015-09-19T17:53:39Z

From: Joe Thornber <ejt@redhat.com>

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>

---
drivers/md/dm-cache-target.c | 4 ++++
1 file changed, 4 insertions(+)

--- 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_d
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(st
remap_to_cache(cache, bio, cblock);
issue(cache, bio);
}
+
+ free_prison_cell(cache, cell);
}

/*----------------------------------------------------------------*/