[dm-devel] [PATCH] dm-zoned: Avoid metadata flush writeback throttling

[Damien Le Moal]

Avoid metadata flush to be blocked by the writeback throttling code in
wbt_wait(). Otherwise, we can end up with a deadlock under heavy write
load with all chunk works active. In such situation, a deadlock can
happen if the flush work is blocked by the throttling code while holding
the metadata lock: as the chunk works will wait for the metadata lock
too, no progress can be made.

Signed-off-by: Damien Le Moal <damien.lemoal at wdc.com>
---
 drivers/md/dm-zoned-metadata.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c
index 884ff7c170a0..f694fb98b002 100644
--- a/drivers/md/dm-zoned-metadata.c
+++ b/drivers/md/dm-zoned-metadata.c
@@ -567,7 +567,8 @@ static void dmz_write_mblock(struct dmz_metadata *zmd, struct dmz_mblock *mblk,
 	bio->bi_bdev = zmd->dev->bdev;
 	bio->bi_private = mblk;
 	bio->bi_end_io = dmz_mblock_bio_end_io;
-	bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_META | REQ_PRIO);
+	bio_set_op_attrs(bio, REQ_OP_WRITE,
+			 REQ_META | REQ_PRIO | REQ_SYNC | REQ_IDLE);
 	bio_add_page(bio, mblk->page, DMZ_BLOCK_SIZE, 0);
 	submit_bio(bio);
 }
-- 
2.13.3