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authorVishal Verma <vverma@digitalocean.com>2021-12-21 20:06:19 +0000
committerSong Liu <song@kernel.org>2022-01-06 08:37:02 -0800
commitf51d46d0e7cb5b8494aa534d276a9d8915a2443d (patch)
tree1fee981ced8826ed051f0f901cdb137b9af44ecb /drivers/md
parenta92ce0feffeed8b91f02dac85246d1205e4a64b6 (diff)
md: add support for REQ_NOWAIT
commit 021a24460dc2 ("block: add QUEUE_FLAG_NOWAIT") added support for checking whether a given bdev supports handling of REQ_NOWAIT or not. Since then commit 6abc49468eea ("dm: add support for REQ_NOWAIT and enable it for linear target") added support for REQ_NOWAIT for dm. This uses a similar approach to incorporate REQ_NOWAIT for md based bios. This patch was tested using t/io_uring tool within FIO. A nvme drive was partitioned into 2 partitions and a simple raid 0 configuration /dev/md0 was created. md0 : active raid0 nvme4n1p1[1] nvme4n1p2[0] 937423872 blocks super 1.2 512k chunks Before patch: $ ./t/io_uring /dev/md0 -p 0 -a 0 -d 1 -r 100 Running top while the above runs: $ ps -eL | grep $(pidof io_uring) 38396 38396 pts/2 00:00:00 io_uring 38396 38397 pts/2 00:00:15 io_uring 38396 38398 pts/2 00:00:13 iou-wrk-38397 We can see iou-wrk-38397 io worker thread created which gets created when io_uring sees that the underlying device (/dev/md0 in this case) doesn't support nowait. After patch: $ ./t/io_uring /dev/md0 -p 0 -a 0 -d 1 -r 100 Running top while the above runs: $ ps -eL | grep $(pidof io_uring) 38341 38341 pts/2 00:10:22 io_uring 38341 38342 pts/2 00:10:37 io_uring After running this patch, we don't see any io worker thread being created which indicated that io_uring saw that the underlying device does support nowait. This is the exact behaviour noticed on a dm device which also supports nowait. For all the other raid personalities except raid0, we would need to train pieces which involves make_request fn in order for them to correctly handle REQ_NOWAIT. Reviewed-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Vishal Verma <vverma@digitalocean.com> Signed-off-by: Song Liu <song@kernel.org>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/md.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 7fbf6f0ac01b..c6de7d4bfe4d 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -418,6 +418,12 @@ check_suspended:
rcu_read_lock();
if (is_suspended(mddev, bio)) {
DEFINE_WAIT(__wait);
+ /* Bail out if REQ_NOWAIT is set for the bio */
+ if (bio->bi_opf & REQ_NOWAIT) {
+ rcu_read_unlock();
+ bio_wouldblock_error(bio);
+ return;
+ }
for (;;) {
prepare_to_wait(&mddev->sb_wait, &__wait,
TASK_UNINTERRUPTIBLE);
@@ -5787,6 +5793,7 @@ int md_run(struct mddev *mddev)
int err;
struct md_rdev *rdev;
struct md_personality *pers;
+ bool nowait = true;
if (list_empty(&mddev->disks))
/* cannot run an array with no devices.. */
@@ -5857,8 +5864,13 @@ int md_run(struct mddev *mddev)
}
}
sysfs_notify_dirent_safe(rdev->sysfs_state);
+ nowait = nowait && blk_queue_nowait(bdev_get_queue(rdev->bdev));
}
+ /* Set the NOWAIT flags if all underlying devices support it */
+ if (nowait)
+ blk_queue_flag_set(QUEUE_FLAG_NOWAIT, mddev->queue);
+
if (!bioset_initialized(&mddev->bio_set)) {
err = bioset_init(&mddev->bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
if (err)
@@ -7003,6 +7015,15 @@ static int hot_add_disk(struct mddev *mddev, dev_t dev)
if (!mddev->thread)
md_update_sb(mddev, 1);
/*
+ * If the new disk does not support REQ_NOWAIT,
+ * disable on the whole MD.
+ */
+ if (!blk_queue_nowait(bdev_get_queue(rdev->bdev))) {
+ pr_info("%s: Disabling nowait because %s does not support nowait\n",
+ mdname(mddev), bdevname(rdev->bdev, b));
+ blk_queue_flag_clear(QUEUE_FLAG_NOWAIT, mddev->queue);
+ }
+ /*
* Kick recovery, maybe this spare has to be added to the
* array immediately.
*/