[PATCH v2 2/4] md/raid10: fix writes_pending leak on write request failures

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

raid10_make_request() acquires a writes_pending reference with
md_write_start() before dispatching write requests. Several failure
paths in raid10_write_request() complete the bio and return without
reaching the normal write completion path, causing the corresponding
md_write_end() to be skipped.

Make raid10_write_request() return a status indicating whether the write
request was successfully queued. This allows raid10_make_request() to
release the writes_pending reference with md_write_end() when a write
request fails.

Fixes: 4cf58d952909 ("md/raid10: Handle bio_split() errors")
Fixes: c9aa889b035f ("md: raid10 add nowait support")
Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
---
Changes in v2:
 - new patch.
---
 drivers/md/raid10.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 5bd7698e0a1b..5ad1b0c6207a 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1349,7 +1349,7 @@ static void wait_blocked_dev(struct mddev *mddev, struct r10bio *r10_bio)
 	}
 }
 
-static void raid10_write_request(struct mddev *mddev, struct bio *bio,
+static bool raid10_write_request(struct mddev *mddev, struct bio *bio,
 				 struct r10bio *r10_bio)
 {
 	struct r10conf *conf = mddev->private;
@@ -1365,7 +1365,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 		/* Bail out if REQ_NOWAIT is set for the bio */
 		if (bio->bi_opf & REQ_NOWAIT) {
 			bio_wouldblock_error(bio);
-			return;
+			return false;
 		}
 		for (;;) {
 			prepare_to_wait(&conf->wait_barrier,
@@ -1381,7 +1381,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 	sectors = r10_bio->sectors;
 	if (!regular_request_wait(mddev, conf, bio, sectors)) {
 		free_r10bio(r10_bio);
-		return;
+		return false;
 	}
 
 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
@@ -1398,7 +1398,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 		if (bio->bi_opf & REQ_NOWAIT) {
 			allow_barrier(conf);
 			bio_wouldblock_error(bio);
-			return;
+			return false;
 		}
 		mddev_add_trace_msg(conf->mddev,
 			"raid10 wait reshape metadata");
@@ -1514,7 +1514,8 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 			raid10_write_one_disk(mddev, r10_bio, bio, true, i);
 	}
 	one_write_done(r10_bio);
-	return;
+	return true;
+
 err_handle:
 	for (k = 0;  k < i; k++) {
 		int d = r10_bio->devs[k].devnum;
@@ -1532,10 +1533,12 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 	}
 
 	raid_end_bio_io(r10_bio);
+	return false;
 }
 
-static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
+static bool __make_request(struct mddev *mddev, struct bio *bio, int sectors)
 {
+	bool ret;
 	struct r10conf *conf = mddev->private;
 	struct r10bio *r10_bio;
 
@@ -1551,10 +1554,13 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
 	memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) *
 			conf->geo.raid_disks);
 
+	ret = true;
 	if (bio_data_dir(bio) == READ)
 		raid10_read_request(mddev, bio, r10_bio);
 	else
-		raid10_write_request(mddev, bio, r10_bio);
+		ret = raid10_write_request(mddev, bio, r10_bio);
+
+	return ret;
 }
 
 static void raid_end_discard_bio(struct r10bio *r10bio)
@@ -1900,7 +1906,8 @@ static bool raid10_make_request(struct mddev *mddev, struct bio *bio)
 		sectors = chunk_sects -
 			(bio->bi_iter.bi_sector &
 			 (chunk_sects - 1));
-	__make_request(mddev, bio, sectors);
+	if (!__make_request(mddev, bio, sectors))
+		md_write_end(mddev);
 
 	/* In case raid10d snuck in to freeze_array */
 	wake_up_barrier(conf);
-- 
2.43.0