dm thin: reinstate missing mempool_free in cell_release_singleton

commit 03aaae7cdc71bc306888440b1f569d463e917b6d upstream.

Fix a significant memory leak inadvertently introduced during
simplification of cell_release_singleton() in commit
6f94a4c45a6f744383f9f695dde019998db3df55 ("dm thin: fix stacked bi_next
usage").

A cell's hlist_del() must be accompanied by a mempool_free().
Use __cell_release() to do this, like before.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index da2f0217df666fcc087ef9b28da40319a393435e..532a9029c2aee147f71cbf6f821b6c1b10462378 100644 (file)
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -288,8 +288,10 @@ static void __cell_release(struct cell *cell, struct bio_list *inmates)
 
        hlist_del(&cell->list);
 
-       bio_list_add(inmates, cell->holder);
-       bio_list_merge(inmates, &cell->bios);
+       if (inmates) {
+               bio_list_add(inmates, cell->holder);
+               bio_list_merge(inmates, &cell->bios);
+       }
 
        mempool_free(cell, prison->cell_pool);
 }
@@ -312,9 +314,10 @@ static void cell_release(struct cell *cell, struct bio_list *bios)
  */
 static void __cell_release_singleton(struct cell *cell, struct bio *bio)
 {
-       hlist_del(&cell->list);
        BUG_ON(cell->holder != bio);
        BUG_ON(!bio_list_empty(&cell->bios));
+
+       __cell_release(cell, NULL);
 }
 
 static void cell_release_singleton(struct cell *cell, struct bio *bio)