[dm-devel] [PATCH 3/9] md: raid1 nowait support
Goldwyn Rodrigues
rgoldwyn at suse.de
Wed Jul 26 23:58:00 UTC 2017
From: Goldwyn Rodrigues <rgoldwyn at suse.com>
The RAID1 driver would bail with EAGAIN in case of:
+ I/O has to wait for a barrier
+ array is frozen
+ Area is suspended
+ There are too many pending I/O that it will be queued.
To facilitate error for wait barriers, wait_barrier() is
returning bool. True in case if there was a wait (or is not
required). False in case a wait was required, but was not performed.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn at suse.com>
---
drivers/md/raid1.c | 74 +++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 57 insertions(+), 17 deletions(-)
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 3febfc8391fb..66ca4288e3e8 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -903,8 +903,9 @@ static void lower_barrier(struct r1conf *conf, sector_t sector_nr)
wake_up(&conf->wait_barrier);
}
-static void _wait_barrier(struct r1conf *conf, int idx)
+static bool _wait_barrier(struct r1conf *conf, int idx, bool nowait)
{
+ bool ret = true;
/*
* We need to increase conf->nr_pending[idx] very early here,
* then raise_barrier() can be blocked when it waits for
@@ -935,7 +936,7 @@ static void _wait_barrier(struct r1conf *conf, int idx)
*/
if (!READ_ONCE(conf->array_frozen) &&
!atomic_read(&conf->barrier[idx]))
- return;
+ return ret;
/*
* After holding conf->resync_lock, conf->nr_pending[idx]
@@ -953,18 +954,26 @@ static void _wait_barrier(struct r1conf *conf, int idx)
*/
wake_up(&conf->wait_barrier);
/* Wait for the barrier in same barrier unit bucket to drop. */
- wait_event_lock_irq(conf->wait_barrier,
- !conf->array_frozen &&
- !atomic_read(&conf->barrier[idx]),
- conf->resync_lock);
+ if (conf->array_frozen || atomic_read(&conf->barrier[idx])) {
+ if (nowait)
+ ret = false;
+ else
+ wait_event_lock_irq(conf->wait_barrier,
+ !conf->array_frozen &&
+ !atomic_read(&conf->barrier[idx]),
+ conf->resync_lock);
+ }
atomic_inc(&conf->nr_pending[idx]);
atomic_dec(&conf->nr_waiting[idx]);
spin_unlock_irq(&conf->resync_lock);
+ return ret;
}
-static void wait_read_barrier(struct r1conf *conf, sector_t sector_nr)
+static bool wait_read_barrier(struct r1conf *conf, sector_t sector_nr,
+ bool nowait)
{
int idx = sector_to_idx(sector_nr);
+ bool ret = true;
/*
* Very similar to _wait_barrier(). The difference is, for read
@@ -976,7 +985,7 @@ static void wait_read_barrier(struct r1conf *conf, sector_t sector_nr)
atomic_inc(&conf->nr_pending[idx]);
if (!READ_ONCE(conf->array_frozen))
- return;
+ return ret;
spin_lock_irq(&conf->resync_lock);
atomic_inc(&conf->nr_waiting[idx]);
@@ -987,19 +996,28 @@ static void wait_read_barrier(struct r1conf *conf, sector_t sector_nr)
*/
wake_up(&conf->wait_barrier);
/* Wait for array to be unfrozen */
- wait_event_lock_irq(conf->wait_barrier,
- !conf->array_frozen,
- conf->resync_lock);
+ if (conf->array_frozen) {
+ /* If nowait flag is set, return false to
+ * show we did not wait
+ */
+ if (nowait)
+ ret = false;
+ else
+ wait_event_lock_irq(conf->wait_barrier,
+ !conf->array_frozen,
+ conf->resync_lock);
+ }
atomic_inc(&conf->nr_pending[idx]);
atomic_dec(&conf->nr_waiting[idx]);
spin_unlock_irq(&conf->resync_lock);
+ return ret;
}
-static void wait_barrier(struct r1conf *conf, sector_t sector_nr)
+static bool wait_barrier(struct r1conf *conf, sector_t sector_nr, bool nowait)
{
int idx = sector_to_idx(sector_nr);
- _wait_barrier(conf, idx);
+ return _wait_barrier(conf, idx, nowait);
}
static void wait_all_barriers(struct r1conf *conf)
@@ -1007,7 +1025,7 @@ static void wait_all_barriers(struct r1conf *conf)
int idx;
for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++)
- _wait_barrier(conf, idx);
+ _wait_barrier(conf, idx, false);
}
static void _allow_barrier(struct r1conf *conf, int idx)
@@ -1223,7 +1241,11 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
* Still need barrier for READ in case that whole
* array is frozen.
*/
- wait_read_barrier(conf, bio->bi_iter.bi_sector);
+ if (!wait_read_barrier(conf, bio->bi_iter.bi_sector,
+ bio->bi_opf & REQ_NOWAIT)) {
+ bio_wouldblock_error(bio);
+ return;
+ }
if (!r1_bio)
r1_bio = alloc_r1bio(mddev, bio);
@@ -1333,6 +1355,11 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
* an interruptible wait.
*/
DEFINE_WAIT(w);
+ if (bio->bi_opf & REQ_NOWAIT) {
+ bio_wouldblock_error(bio);
+ return;
+ }
+
for (;;) {
sigset_t full, old;
prepare_to_wait(&conf->wait_barrier,
@@ -1351,7 +1378,11 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
}
finish_wait(&conf->wait_barrier, &w);
}
- wait_barrier(conf, bio->bi_iter.bi_sector);
+ if (!wait_barrier(conf, bio->bi_iter.bi_sector,
+ bio->bi_opf & REQ_NOWAIT)) {
+ bio_wouldblock_error(bio);
+ return;
+ }
r1_bio = alloc_r1bio(mddev, bio);
r1_bio->sectors = max_write_sectors;
@@ -1359,6 +1390,10 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
if (conf->pending_count >= max_queued_requests) {
md_wakeup_thread(mddev->thread);
raid1_log(mddev, "wait queued");
+ if (bio->bi_opf & REQ_NOWAIT) {
+ bio_wouldblock_error(bio);
+ return;
+ }
wait_event(conf->wait_barrier,
conf->pending_count < max_queued_requests);
}
@@ -1442,6 +1477,11 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
/* Wait for this device to become unblocked */
int j;
+ if (bio->bi_opf & REQ_NOWAIT) {
+ bio_wouldblock_error(bio);
+ return;
+ }
+
for (j = 0; j < i; j++)
if (r1_bio->bios[j])
rdev_dec_pending(conf->mirrors[j].rdev, mddev);
@@ -1449,7 +1489,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
allow_barrier(conf, bio->bi_iter.bi_sector);
raid1_log(mddev, "wait rdev %d blocked", blocked_rdev->raid_disk);
md_wait_for_blocked_rdev(blocked_rdev, mddev);
- wait_barrier(conf, bio->bi_iter.bi_sector);
+ wait_barrier(conf, bio->bi_iter.bi_sector, false);
goto retry_write;
}
--
2.12.3
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