We used to insert the data commands following a pre-flush to the head
of the queue until commit 1e82fadfc6b ("blk-mq: do not do head insertions
post-pre-flush commands"). Not doing this seems to cause hangs of
such commands on NFS workloads when exported from file systems with
SATA SSDs. I have no idea why this would starve these workloads,
but doing a semantic revert of this patch (which looks quite different
due to various other changes) fixes the hangs.
Fixes: 1e82fadfc6b ("blk-mq: do not do head insertions post-pre-flush commands")
Reported-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Tested-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
block/blk-flush.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-flush.c b/block/blk-flush.c
index dba392cf22bec6..8220517c2d67da 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -189,7 +189,7 @@ static void blk_flush_complete_seq(struct request *rq,
case REQ_FSEQ_DATA:
list_move_tail(&rq->flush.list, &fq->flush_data_in_flight);
spin_lock(&q->requeue_lock);
- list_add_tail(&rq->queuelist, &q->flush_list);
+ list_add(&rq->queuelist, &q->requeue_list);
spin_unlock(&q->requeue_lock);
blk_mq_kick_requeue_list(q);
break;
--
2.39.2
