[PATCH v2 3/4] md/raid10: fix writes_pending and barrier reference leaks on discard failures

[Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>]

raid10_make_request() acquires a writes_pending reference with
md_write_start() before calling raid10_handle_discard(). Several failure
paths in raid10_handle_discard() complete the bio and return without
releasing the corresponding reference, causing md_write_end() to be
skipped.

Call md_write_end() before returning from these failure paths to keep
writes_pending accounting balanced.

Additionally, discard split allocation failures can occur after
wait_barrier() succeeds. Those paths return without calling
allow_barrier(), leaking the associated barrier reference.

Release the barrier before returning from those paths.

Fixes: c9aa889b035f ("md: raid10 add nowait support")
Fixes: 4cf58d952909 ("md/raid10: Handle bio_split() errors")
Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
---
Changes in v2:
 - new patch.
---
 drivers/md/raid10.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 5ad1b0c6207a..aacf160ee9f2 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1639,6 +1639,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 
 	if (!wait_barrier(conf, bio->bi_opf & REQ_NOWAIT)) {
 		bio_wouldblock_error(bio);
+		md_write_end(mddev);
 		return 0;
 	}
 
@@ -1681,6 +1682,8 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 		if (IS_ERR(split)) {
 			bio->bi_status = errno_to_blk_status(PTR_ERR(split));
 			bio_endio(bio);
+			md_write_end(mddev);
+			allow_barrier(conf);
 			return 0;
 		}
 
@@ -1698,6 +1701,8 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 		if (IS_ERR(split)) {
 			bio->bi_status = errno_to_blk_status(PTR_ERR(split));
 			bio_endio(bio);
+			md_write_end(mddev);
+			allow_barrier(conf);
 			return 0;
 		}
 
-- 
2.43.0