On 08/08/2017 03:39 PM, Shaohua Li wrote:
> On Wed, Jul 26, 2017 at 06:58:00PM -0500, Goldwyn Rodrigues wrote:
>> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>>
>> 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@xxxxxxxx>
>> ---
>> 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;
>
> In this case, we nr_pending shouldn't be increased
Ok, will fix this.
>
>> + 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;
>
> ditto
>> + 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);
>
> There are other cases we could block, for example, md_wait_for_blocked_rdev
> here. Is the goal just avoid block for normal situations?
Isn't this covered by the if condition of the codeblock (blocked_rdev !=
NULL)?
>
>> goto retry_write;
>> }
>>
>> --
>> 2.12.3
>>
>> --
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--
Goldwyn
