[PATCH 1/2] Btrfs: fix memory leak of transaction when deleting unused block group

[fdmanana@kernel.org]

From: Filipe Manana <fdmanana@suse.com>

When cleaning pinned extents right before deleting an unused block group,
we check if there's still a previous transaction running and if so we
increment its reference count before using it for cleaning pinned ranges
in its pinned extents iotree. However we ended up never decrementing the
reference count after using the transaction, resulting in a memory leak.

Fix it by decrementing the reference count.

Fixes: fe119a6eeb6705 ("btrfs: switch to per-transaction pinned extents")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/block-group.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 47f66c6a7d7f..93c180ffcb80 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1288,11 +1288,15 @@ static bool clean_pinned_extents(struct btrfs_trans_handle *trans,
 	if (ret)
 		goto err;
 	mutex_unlock(&fs_info->unused_bg_unpin_mutex);
+	if (prev_trans)
+		refcount_dec(&prev_trans->use_count);
 
 	return true;
 
 err:
 	mutex_unlock(&fs_info->unused_bg_unpin_mutex);
+	if (prev_trans)
+		refcount_dec(&prev_trans->use_count);
 	btrfs_dec_block_group_ro(bg);
 	return false;
 }
-- 
2.11.0