6.11-stable review patch. If anyone has any objections, please let me know.
------------------
From: Christoph Hellwig <hch@xxxxxx>
[ Upstream commit 7f212e997edbb7a2cb85cef2ac14265dfaf88717 ]
blk_mq_flush_plug_list submits requests in the reverse order that they
were submitted, which leads to a rather suboptimal I/O pattern
especially in rotational devices. Fix this by rewriting virtio_queue_rqs
so that it always pops the requests from the passed in request list, and
then adds them to the head of a local submit list. This actually
simplifies the code a bit as it removes the complicated list splicing,
at the cost of extra updates of the rq_next pointer. As that should be
cache hot anyway it should be an easy price to pay.
Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Link: https://lore.kernel.org/r/20241113152050.157179-3-hch@xxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/block/virtio_blk.c | 46 +++++++++++++++++---------------------
1 file changed, 21 insertions(+), 25 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 194417abc1053..43c96b73a7118 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -471,18 +471,18 @@ static bool virtblk_prep_rq_batch(struct request *req)
return virtblk_prep_rq(req->mq_hctx, vblk, req, vbr) == BLK_STS_OK;
}
-static bool virtblk_add_req_batch(struct virtio_blk_vq *vq,
+static void virtblk_add_req_batch(struct virtio_blk_vq *vq,
struct request **rqlist)
{
+ struct request *req;
unsigned long flags;
- int err;
bool kick;
spin_lock_irqsave(&vq->lock, flags);
- while (!rq_list_empty(*rqlist)) {
- struct request *req = rq_list_pop(rqlist);
+ while ((req = rq_list_pop(rqlist))) {
struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
+ int err;
err = virtblk_add_req(vq->vq, vbr);
if (err) {
@@ -495,37 +495,33 @@ static bool virtblk_add_req_batch(struct virtio_blk_vq *vq,
kick = virtqueue_kick_prepare(vq->vq);
spin_unlock_irqrestore(&vq->lock, flags);
- return kick;
+ if (kick)
+ virtqueue_notify(vq->vq);
}
static void virtio_queue_rqs(struct request **rqlist)
{
- struct request *req, *next, *prev = NULL;
+ struct request *submit_list = NULL;
struct request *requeue_list = NULL;
+ struct request **requeue_lastp = &requeue_list;
+ struct virtio_blk_vq *vq = NULL;
+ struct request *req;
- rq_list_for_each_safe(rqlist, req, next) {
- struct virtio_blk_vq *vq = get_virtio_blk_vq(req->mq_hctx);
- bool kick;
-
- if (!virtblk_prep_rq_batch(req)) {
- rq_list_move(rqlist, &requeue_list, req, prev);
- req = prev;
- if (!req)
- continue;
- }
+ while ((req = rq_list_pop(rqlist))) {
+ struct virtio_blk_vq *this_vq = get_virtio_blk_vq(req->mq_hctx);
- if (!next || req->mq_hctx != next->mq_hctx) {
- req->rq_next = NULL;
- kick = virtblk_add_req_batch(vq, rqlist);
- if (kick)
- virtqueue_notify(vq->vq);
+ if (vq && vq != this_vq)
+ virtblk_add_req_batch(vq, &submit_list);
+ vq = this_vq;
- *rqlist = next;
- prev = NULL;
- } else
- prev = req;
+ if (virtblk_prep_rq_batch(req))
+ rq_list_add(&submit_list, req); /* reverse order */
+ else
+ rq_list_add_tail(&requeue_lastp, req);
}
+ if (vq)
+ virtblk_add_req_batch(vq, &submit_list);
*rqlist = requeue_list;
}
--
2.43.0
