The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 67205f80be9910207481406c47f7d85e703fb2e9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '167812499941176@kroah.com' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

67205f80be99 ("brd: mark as nowait compatible") e1528830bd4e ("block/brd: add error handling support for add_disk()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 67205f80be9910207481406c47f7d85e703fb2e9 Mon Sep 17 00:00:00 2001 From: Jens Axboe axboe@kernel.dk Date: Wed, 15 Feb 2023 16:43:47 -0700 Subject: [PATCH] brd: mark as nowait compatible

By default, non-mq drivers do not support nowait. This causes io_uring to use a slower path as the driver cannot be trust not to block. brd can safely set the nowait flag, as worst case all it does is a NOIO allocation.

For io_uring, this makes a substantial difference. Before:

submitter=0, tid=453, file=/dev/ram0, node=-1 polled=0, fixedbufs=1/0, register_files=1, buffered=0, QD=128 Engine=io_uring, sq_ring=128, cq_ring=128 IOPS=440.03K, BW=1718MiB/s, IOS/call=32/31 IOPS=428.96K, BW=1675MiB/s, IOS/call=32/32 IOPS=442.59K, BW=1728MiB/s, IOS/call=32/31 IOPS=419.65K, BW=1639MiB/s, IOS/call=32/32 IOPS=426.82K, BW=1667MiB/s, IOS/call=32/31

and after:

submitter=0, tid=354, file=/dev/ram0, node=-1 polled=0, fixedbufs=1/0, register_files=1, buffered=0, QD=128 Engine=io_uring, sq_ring=128, cq_ring=128 IOPS=3.37M, BW=13.15GiB/s, IOS/call=32/31 IOPS=3.45M, BW=13.46GiB/s, IOS/call=32/31 IOPS=3.43M, BW=13.42GiB/s, IOS/call=32/32 IOPS=3.43M, BW=13.39GiB/s, IOS/call=32/31 IOPS=3.43M, BW=13.38GiB/s, IOS/call=32/31

or about an 8x in difference. Now that brd is prepared to deal with REQ_NOWAIT reads/writes, mark it as supporting that.

Cc: stable@vger.kernel.org # 5.10+ Link: https://lore.kernel.org/linux-block/20230203103005.31290-1-p.raghav@samsung.... Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/drivers/block/brd.c b/drivers/block/brd.c index 00f3c5b51a01..740631dcdd0e 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -418,6 +418,7 @@ static int brd_alloc(int i) /* Tell the block layer that this is not a rotational device */ blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue); blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue); + blk_queue_flag_set(QUEUE_FLAG_NOWAIT, disk->queue); err = add_disk(disk); if (err) goto out_cleanup_disk;