Btrfs: fix memory leaks after transaction is aborted

When a transaction is aborted, or its commit fails before writing the new
superblock and calling btrfs_finish_extent_commit(), we leak reference
counts on the block groups attached to the transaction's delete_bgs list,
because btrfs_finish_extent_commit() is never called for those two cases.
Fix this by dropping their references at btrfs_put_transaction(), which
is called when transactions are aborted (by making the transaction kthread
commit the transaction) or if their commits fail.

Signed-off-by: Filipe Manana <fdmanana@suse.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index be8eae80ff65..f85ccf634ca1 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -75,6 +75,23 @@ void btrfs_put_transaction(struct btrfs_transaction *transaction)
                         list_del_init(&em->list);
                         free_extent_map(em);
                 }
+                /*
+                 * If any block groups are found in ->deleted_bgs then it's
+                 * because the transaction was aborted and a commit did not
+                 * happen (things failed before writing the new superblock
+                 * and calling btrfs_finish_extent_commit()), so we can not
+                 * discard the physical locations of the block groups.
+                 */
+                while (!list_empty(&transaction->deleted_bgs)) {
+                        struct btrfs_block_group_cache *cache;
+
+                        cache = list_first_entry(&transaction->deleted_bgs,
+                                                 struct btrfs_block_group_cache,
+                                                 bg_list);
+                        list_del_init(&cache->bg_list);
+                        btrfs_put_block_group_trimming(cache);
+                        btrfs_put_block_group(cache);
+                }
                 kmem_cache_free(btrfs_transaction_cachep, transaction);
         }
 }