From: Pankaj Gupta <pagupta@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-nvdimm <linux-nvdimm@lists.01.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux ACPI <linux-acpi@vger.kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <lenb@kernel.org>
Subject: Re: [PATCH] virtio pmem: fix async flush ordering
Date: Fri, 22 Nov 2019 00:37:00 -0500 (EST) [thread overview]
Message-ID: <838611538.35971353.1574401020319.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <CAPcyv4gsQXY5C5URF2vrTaD-0Q_CJ+ib3GVb1VFZAO+1Gdau2w@mail.gmail.com>
> > > > > >
> > > > > > I added that and was about to push this out, but what about the
> > > > > > fact
> > > > > > that now the guest will synchronously wait for flushing to occur.
> > > > > > The
> > > > > > goal of the child bio was to allow that to be an I/O wait with
> > > > > > overlapping I/O, or at least not blocking the submission thread.
> > > > > > Does
> > > > > > the block layer synchronously wait for PREFLUSH requests? If not I
> > > > > > think a synchronous wait is going to be a significant performance
> > > > > > regression. Are there any numbers to accompany this change?
> > > > >
> > > > > Why not just swap the parent child relationship in the PREFLUSH case?
> > > >
> > > > I we are already inside parent bio "make_request" function and we
> > > > create
> > > > child
> > > > bio. How we exactly will swap the parent/child relationship for
> > > > PREFLUSH
> > > > case?
> > > >
> > > > Child bio is queued after parent bio completes.
> > >
> > > Sorry, I didn't quite mean with bio_split, but issuing another request
> > > in front of the real bio. See md_flush_request() for inspiration.
> >
> > o.k. Thank you. Will try to post patch today to be considered for 5.4.
> >
>
> I think it is too late for v5.4-final, but we can get it in the
> -stable queue. Let's take the time to do it right and get some testing
> on it.
Sure.
Just sharing probable patch for early feedback, if I am doing it correctly?
I will test it thoroughly.
Thanks,
Pankaj
========
diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
index 10351d5b49fa..c683e0e2515c 100644
--- a/drivers/nvdimm/nd_virtio.c
+++ b/drivers/nvdimm/nd_virtio.c
@@ -112,6 +112,12 @@ int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)
bio_copy_dev(child, bio);
child->bi_opf = REQ_PREFLUSH;
child->bi_iter.bi_sector = -1;
+
+ if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
+ struct request_queue *q = bio->bi_disk->queue;
+ q->make_request_fn(q, child);
+ return 0;
+ }
bio_chain(child, bio);
submit_bio(child);
return 0;
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next prev parent reply other threads:[~2019-11-22 5:37 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-20 9:28 [PATCH] virtio pmem: fix async flush ordering Pankaj Gupta
2019-11-20 17:26 ` Jeff Moyer
2019-11-21 6:44 ` Pankaj Gupta
2019-11-21 7:23 ` Dan Williams
2019-11-21 7:32 ` Dan Williams
2019-11-21 8:00 ` Pankaj Gupta
2019-11-21 16:09 ` Dan Williams
2019-11-22 4:38 ` Pankaj Gupta
2019-11-22 5:17 ` Dan Williams
2019-11-22 5:37 ` Pankaj Gupta [this message]
2019-11-22 22:52 ` Dan Williams
2019-11-21 8:01 ` Pankaj Gupta
2019-11-22 16:08 ` Jeff Moyer
2019-11-22 16:13 ` Dan Williams
2019-11-22 16:25 ` Jeff Moyer
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