[dm-devel] [PATCH 4/9] md: raid5 nowait support

[Goldwyn Rodrigues]

On 08/08/2017 03:43 PM, Shaohua Li wrote:
> On Wed, Jul 26, 2017 at 06:58:01PM -0500, Goldwyn Rodrigues wrote:
>> From: Goldwyn Rodrigues <rgoldwyn at suse.com>
>>
>> Return EAGAIN in case RAID5 would block because of waiting due to:
>>  + Reshaping
>>  + Suspension
>>  + Stripe Expansion
>>
>> Signed-off-by: Goldwyn Rodrigues <rgoldwyn at suse.com>
>> ---
>>  drivers/md/raid5.c | 20 ++++++++++++++++++++
>>  1 file changed, 20 insertions(+)
>>
>> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>> index aeeb8d6854e2..d1b3bcf26d29 100644
>> --- a/drivers/md/raid5.c
>> +++ b/drivers/md/raid5.c
>> @@ -5635,6 +5635,11 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
>>  				    ? logical_sector < conf->reshape_safe
>>  				    : logical_sector >= conf->reshape_safe) {
>>  					spin_unlock_irq(&conf->device_lock);
>> +					if (bi->bi_opf & REQ_NOWAIT) {
>> +						bio_wouldblock_error(bi);
>> +						finish_wait(&conf->wait_for_overlap, &w);
>> +						return true;
>> +					}
> 
> A bio could use several stripes. If one stripe block, simpliy return bio here
> doesn't really make the whole bio finish.

My understanding is a little weak here.
How would you have to terminate the entire bio since one of the stripes
is blocking?

> 
>>  					schedule();
>>  					do_prepare = true;
>>  					goto retry;
>> @@ -5672,6 +5677,11 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
>>  				spin_unlock_irq(&conf->device_lock);
>>  				if (must_retry) {
>>  					raid5_release_stripe(sh);
>> +					if (bi->bi_opf & REQ_NOWAIT) {
>> +						bio_wouldblock_error(bi);
>> +						finish_wait(&conf->wait_for_overlap, &w);
>> +						return true;
>> +					}
>>  					schedule();
>>  					do_prepare = true;
>>  					goto retry;
>> @@ -5700,6 +5710,11 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
>>  					sigset_t full, old;
>>  					sigfillset(&full);
>>  					sigprocmask(SIG_BLOCK, &full, &old);
>> +					if (bi->bi_opf & REQ_NOWAIT) {
>> +						bio_wouldblock_error(bi);
>> +						finish_wait(&conf->wait_for_overlap, &w);
>> +						return true;
>> +					}
>>  					schedule();
>>  					sigprocmask(SIG_SETMASK, &old, NULL);
>>  					do_prepare = true;
>> @@ -5715,6 +5730,11 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
>>  				 */
>>  				md_wakeup_thread(mddev->thread);
>>  				raid5_release_stripe(sh);
>> +				if (bi->bi_opf & REQ_NOWAIT) {
>> +					bio_wouldblock_error(bi);
>> +					finish_wait(&conf->wait_for_overlap, &w);
>> +					return true;
>> +				}
>>  				schedule();
>>  				do_prepare = true;
>>  				goto retry;
>> -- 
>> 2.12.3
>>
>> --
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-- 
Goldwyn