On 11/3/20 9:48 PM, Mike Snitzer wrote:
On Tue, Nov 03 2020 at 4:23am -0500,
Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx> wrote:
Hi Mike,
Why queue_work() is unnecessary here for bio with BLK_STS_DM_REQUEUE
returned?
Thanks
Jeffle Xu
---
drivers/md/dm.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c18fc2548518..ae550daa99b5 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -908,9 +908,11 @@ static void dec_pending(struct dm_io *io, blk_status_t error)
* Target requested pushing back the I/O.
*/
spin_lock_irqsave(&md->deferred_lock, flags);
- if (__noflush_suspending(md))
+ if (__noflush_suspending(md)) {
/* NOTE early return due to BLK_STS_DM_REQUEUE below */
bio_list_add_head(&md->deferred, io->orig_bio);
+ queue_work(md->wq, &md->work);
+ }
else
/* noflush suspend was interrupted. */
io->status = BLK_STS_IOERR;
--
2.27.0
For the case you highlighted (BLK_STS_DM_REQUEUE + __noflush_suspending)
I think the missing queue_work is because we're actively dealing with
the fact that we do _not_ want to flush IO. SO kicking the workqueue
there isn't helpful because it just processes work that cannot be issued
yet -- the workqueue will be kicked upon resume (see __dm_resume's
dm_queue_flush).
Got it. Thanks.
If we are in process of DMF_NOFLUSH_SUSPENDING, then the BLK_STS_DM_REQUEUE
may be impacted by the suspending, then re-enqueue the bio to @deferred
list. Or just pop
out BLK_STS_IOERR error.
--
Jeffle
Thanks
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