Re: [PATCH 4/9] md: raid5 nowait support

On 08/08/2017 03:43 PM, Shaohua Li wrote:

On Wed, Jul 26, 2017 at 06:58:01PM -0500, Goldwyn Rodrigues wrote:

quoted

From: Goldwyn Rodrigues <redacted>

Return EAGAIN in case RAID5 would block because of waiting due to:
 + Reshaping
 + Suspension
 + Stripe Expansion

Signed-off-by: Goldwyn Rodrigues <redacted>
---
 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?

quoted

 					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