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md: raid10 add nowait support
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This adds nowait support to the RAID10 driver. Very similar to
raid1 driver changes. It makes RAID10 driver return with EAGAIN
for situations where it could wait for eg:

  - Waiting for the barrier,
  - Reshape operation,
  - Discard operation.

wait_barrier() and regular_request_wait() fn are modified to return bool
to support error for wait barriers. They returns true in case of wait
or if wait is not required and returns false if wait was required
but not performed to support nowait.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Vishal Verma <vverma@digitalocean.com>
Signed-off-by: Song Liu <song@kernel.org>
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Vishal Verma authored and Song Liu committed Jan 6, 2022
1 parent 5aa7050 commit c9aa889
Showing 1 changed file with 67 additions and 33 deletions.
100 changes: 67 additions & 33 deletions drivers/md/raid10.c
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Original file line number Diff line number Diff line change
Expand Up @@ -952,8 +952,10 @@ static void lower_barrier(struct r10conf *conf)
wake_up(&conf->wait_barrier);
}

static void wait_barrier(struct r10conf *conf)
static bool wait_barrier(struct r10conf *conf, bool nowait)
{
bool ret = true;

spin_lock_irq(&conf->resync_lock);
if (conf->barrier) {
struct bio_list *bio_list = current->bio_list;
Expand All @@ -967,27 +969,35 @@ static void wait_barrier(struct r10conf *conf)
* that queue to get the nr_pending
* count down.
*/
raid10_log(conf->mddev, "wait barrier");
wait_event_lock_irq(conf->wait_barrier,
!conf->barrier ||
(atomic_read(&conf->nr_pending) &&
bio_list &&
(!bio_list_empty(&bio_list[0]) ||
!bio_list_empty(&bio_list[1]))) ||
/* move on if recovery thread is
* blocked by us
*/
(conf->mddev->thread->tsk == current &&
test_bit(MD_RECOVERY_RUNNING,
&conf->mddev->recovery) &&
conf->nr_queued > 0),
conf->resync_lock);
/* Return false when nowait flag is set */
if (nowait) {
ret = false;
} else {
raid10_log(conf->mddev, "wait barrier");
wait_event_lock_irq(conf->wait_barrier,
!conf->barrier ||
(atomic_read(&conf->nr_pending) &&
bio_list &&
(!bio_list_empty(&bio_list[0]) ||
!bio_list_empty(&bio_list[1]))) ||
/* move on if recovery thread is
* blocked by us
*/
(conf->mddev->thread->tsk == current &&
test_bit(MD_RECOVERY_RUNNING,
&conf->mddev->recovery) &&
conf->nr_queued > 0),
conf->resync_lock);
}
conf->nr_waiting--;
if (!conf->nr_waiting)
wake_up(&conf->wait_barrier);
}
atomic_inc(&conf->nr_pending);
/* Only increment nr_pending when we wait */
if (ret)
atomic_inc(&conf->nr_pending);
spin_unlock_irq(&conf->resync_lock);
return ret;
}

static void allow_barrier(struct r10conf *conf)
Expand Down Expand Up @@ -1098,21 +1108,30 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
* currently.
* 2. If IO spans the reshape position. Need to wait for reshape to pass.
*/
static void regular_request_wait(struct mddev *mddev, struct r10conf *conf,
static bool regular_request_wait(struct mddev *mddev, struct r10conf *conf,
struct bio *bio, sector_t sectors)
{
wait_barrier(conf);
/* Bail out if REQ_NOWAIT is set for the bio */
if (!wait_barrier(conf, bio->bi_opf & REQ_NOWAIT)) {
bio_wouldblock_error(bio);
return false;
}
while (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
bio->bi_iter.bi_sector < conf->reshape_progress &&
bio->bi_iter.bi_sector + sectors > conf->reshape_progress) {
raid10_log(conf->mddev, "wait reshape");
allow_barrier(conf);
if (bio->bi_opf & REQ_NOWAIT) {
bio_wouldblock_error(bio);
return false;
}
raid10_log(conf->mddev, "wait reshape");
wait_event(conf->wait_barrier,
conf->reshape_progress <= bio->bi_iter.bi_sector ||
conf->reshape_progress >= bio->bi_iter.bi_sector +
sectors);
wait_barrier(conf);
wait_barrier(conf, false);
}
return true;
}

static void raid10_read_request(struct mddev *mddev, struct bio *bio,
Expand Down Expand Up @@ -1157,7 +1176,8 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
rcu_read_unlock();
}

regular_request_wait(mddev, conf, bio, r10_bio->sectors);
if (!regular_request_wait(mddev, conf, bio, r10_bio->sectors))
return;
rdev = read_balance(conf, r10_bio, &max_sectors);
if (!rdev) {
if (err_rdev) {
Expand All @@ -1179,7 +1199,7 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
bio_chain(split, bio);
allow_barrier(conf);
submit_bio_noacct(bio);
wait_barrier(conf);
wait_barrier(conf, false);
bio = split;
r10_bio->master_bio = bio;
r10_bio->sectors = max_sectors;
Expand Down Expand Up @@ -1338,7 +1358,7 @@ static void wait_blocked_dev(struct mddev *mddev, struct r10bio *r10_bio)
raid10_log(conf->mddev, "%s wait rdev %d blocked",
__func__, blocked_rdev->raid_disk);
md_wait_for_blocked_rdev(blocked_rdev, mddev);
wait_barrier(conf);
wait_barrier(conf, false);
goto retry_wait;
}
}
Expand All @@ -1356,6 +1376,11 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
bio->bi_iter.bi_sector,
bio_end_sector(bio)))) {
DEFINE_WAIT(w);
/* Bail out if REQ_NOWAIT is set for the bio */
if (bio->bi_opf & REQ_NOWAIT) {
bio_wouldblock_error(bio);
return;
}
for (;;) {
prepare_to_wait(&conf->wait_barrier,
&w, TASK_IDLE);
Expand All @@ -1368,7 +1393,8 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
}

sectors = r10_bio->sectors;
regular_request_wait(mddev, conf, bio, sectors);
if (!regular_request_wait(mddev, conf, bio, sectors))
return;
if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
(mddev->reshape_backwards
? (bio->bi_iter.bi_sector < conf->reshape_safe &&
Expand All @@ -1380,6 +1406,11 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
set_mask_bits(&mddev->sb_flags, 0,
BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_PENDING));
md_wakeup_thread(mddev->thread);
if (bio->bi_opf & REQ_NOWAIT) {
allow_barrier(conf);
bio_wouldblock_error(bio);
return;
}
raid10_log(conf->mddev, "wait reshape metadata");
wait_event(mddev->sb_wait,
!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));
Expand Down Expand Up @@ -1476,7 +1507,7 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
bio_chain(split, bio);
allow_barrier(conf);
submit_bio_noacct(bio);
wait_barrier(conf);
wait_barrier(conf, false);
bio = split;
r10_bio->master_bio = bio;
}
Expand Down Expand Up @@ -1601,7 +1632,11 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
return -EAGAIN;

wait_barrier(conf);
if (WARN_ON_ONCE(bio->bi_opf & REQ_NOWAIT)) {
bio_wouldblock_error(bio);
return 0;
}
wait_barrier(conf, false);

/*
* Check reshape again to avoid reshape happens after checking
Expand Down Expand Up @@ -1643,7 +1678,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
allow_barrier(conf);
/* Resend the fist split part */
submit_bio_noacct(split);
wait_barrier(conf);
wait_barrier(conf, false);
}
div_u64_rem(bio_end, stripe_size, &remainder);
if (remainder) {
Expand All @@ -1654,7 +1689,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
/* Resend the second split part */
submit_bio_noacct(bio);
bio = split;
wait_barrier(conf);
wait_barrier(conf, false);
}

bio_start = bio->bi_iter.bi_sector;
Expand Down Expand Up @@ -1810,7 +1845,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
end_disk_offset += geo->stride;
atomic_inc(&first_r10bio->remaining);
raid_end_discard_bio(r10_bio);
wait_barrier(conf);
wait_barrier(conf, false);
goto retry_discard;
}

Expand Down Expand Up @@ -2005,7 +2040,7 @@ static void print_conf(struct r10conf *conf)

static void close_sync(struct r10conf *conf)
{
wait_barrier(conf);
wait_barrier(conf, false);
allow_barrier(conf);

mempool_exit(&conf->r10buf_pool);
Expand Down Expand Up @@ -4813,7 +4848,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
if (need_flush ||
time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
/* Need to update reshape_position in metadata */
wait_barrier(conf);
wait_barrier(conf, false);
mddev->reshape_position = conf->reshape_progress;
if (mddev->reshape_backwards)
mddev->curr_resync_completed = raid10_size(mddev, 0, 0)
Expand Down Expand Up @@ -5236,4 +5271,3 @@ MODULE_DESCRIPTION("RAID10 (striped mirror) personality for MD");
MODULE_ALIAS("md-personality-9"); /* RAID10 */
MODULE_ALIAS("md-raid10");
MODULE_ALIAS("md-level-10");

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