[PATCH 6.4 060/800] blk-mq: dont insert passthrough request into sw queue

Greg Kroah-Hartman
2023-07-16T19:56:54Z

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 2293cae703cda162684ae966db6b1b4a11b5e88f ]

In case of real io scheduler, q->elevator is set, so blk_mq_run_hw_queue()
may just check if scheduler queue has request to dispatch, see
__blk_mq_sched_dispatch_requests(). Then IO hang may be caused because
all passthorugh requests may stay in sw queue.

And any passthrough request should have been inserted to hctx->dispatch
always.

Reported-by: Guangwu Zhang <guazhang@redhat.com>
Fixes: d97217e7f024 ("blk-mq: don't queue plugged passthrough requests into scheduler")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230621132208.1142318-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-mq.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c763f0bc66371..b9f4546139894 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2735,7 +2735,12 @@ static void blk_mq_dispatch_plug_list(struct blk_plug *plug, bool from_sched)

percpu_ref_get(&this_hctx->queue->q_usage_counter);
/* passthrough requests should never be issued to the I/O scheduler */
- if (this_hctx->queue->elevator && !is_passthrough) {
+ if (is_passthrough) {
+ spin_lock(&this_hctx->lock);
+ list_splice_tail_init(&list, &this_hctx->dispatch);
+ spin_unlock(&this_hctx->lock);
+ blk_mq_run_hw_queue(this_hctx, from_sched);
+ } else if (this_hctx->queue->elevator) {
this_hctx->queue->elevator->type->ops.insert_requests(this_hctx,
&list, 0);
blk_mq_run_hw_queue(this_hctx, from_sched);
--
2.39.2