From: Mike Snitzer <snitzer@redhat.com>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Kent Overstreet <kmo@daterainc.com>,
"Alasdair G. Kergon" <agk@redhat.com>,
linux-kernel@vger.kernel.org, dm-devel@redhat.com
Subject: Re: block: flush queued bios when the process blocks
Date: Tue, 6 Oct 2015 09:47:53 -0400 [thread overview]
Message-ID: <20151006134753.GA30555@redhat.com> (raw)
In-Reply-To: <alpine.LRH.2.02.1510060919120.23547@file01.intranet.prod.int.rdu2.redhat.com>
On Tue, Oct 06 2015 at 9:28am -0400,
Mikulas Patocka <mpatocka@redhat.com> wrote:
>
>
> On Mon, 5 Oct 2015, Mike Snitzer wrote:
>
> > Mikulas,
> >
> > Could it be that cond_resched() wasn't unplugging? As was
> > recently raised in this thread: https://lkml.org/lkml/2015/9/18/378
> > Chris Mason's patch from that thread fixed this issue... I _think_ Linus
> > has since committed Chris' work but I haven't kept my finger on the
> > pulse of that issue.
>
> I think it doesn't matter (regarding correctness) if cond_reched unplugs
> on not. If it didn't unplug, the process will be scheduled later, and it
> will eventually reach the point where it unplugs.
Couldn't the original deadlock you fixed (as described in your first
patch) manifest when a new process is scheduled?
> > FYI, I've put rebased versions of your 2 patches in my wip branch, see:
> > http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=wip
> >
> > I tweaked the 2nd patch that adds bio_list to plug so that
> > generic_make_request's checks for in_generic_make_request isn't racey
> > (your original patch could happen to have current-plug set but
> > in_generic_make_request not yet set).
>
> I don't recommend that second patch
> (http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/commit/?h=wip&id=5e740c2e45a767d8d6ef8ca36b0db705ef6259c4).
> The patch just complicates things without adding any value. It's also not
> correct because it plugs bios at places when bios aren't supposed to be
> plugged
Avoiding another hook the the scheduler is a requirement (from Jens).
"without adding any value": it offers a different strategy for recording
bios to the bio_list by making it part of the plug. The plug doesn't
actually block bios like requests are plugged. What am I missing?
next prev parent reply other threads:[~2015-10-06 13:47 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-27 15:03 [PATCH] block: flush queued bios when the process blocks Mikulas Patocka
2014-05-27 15:08 ` Jens Axboe
2014-05-27 15:23 ` Mikulas Patocka
2014-05-27 15:42 ` Jens Axboe
2014-05-27 16:26 ` Mikulas Patocka
2014-05-27 17:33 ` Mike Snitzer
2014-05-27 19:56 ` Kent Overstreet
2015-10-05 19:50 ` Mike Snitzer
2014-05-27 17:42 ` [PATCH] " Jens Axboe
2014-05-27 18:14 ` [dm-devel] " Christoph Hellwig
2014-05-27 19:59 ` Kent Overstreet
2014-05-27 19:56 ` Mikulas Patocka
2014-05-27 20:06 ` Kent Overstreet
2014-05-29 23:52 ` Mikulas Patocka
2015-10-05 20:59 ` Mike Snitzer
2015-10-06 13:28 ` Mikulas Patocka
2015-10-06 13:47 ` Mike Snitzer [this message]
2015-10-06 14:10 ` Mikulas Patocka
2015-10-06 14:26 ` Mikulas Patocka
2015-10-06 18:17 ` [dm-devel] " Mikulas Patocka
2015-10-06 18:50 ` Mike Snitzer
2015-10-06 20:16 ` [PATCH v2] " Mike Snitzer
2015-10-06 20:26 ` Mike Snitzer
2015-10-08 15:04 ` Mikulas Patocka
2015-10-08 15:08 ` Mike Snitzer
2015-10-09 19:52 ` Mike Snitzer
2015-10-09 19:59 ` Mike Snitzer
2015-10-14 20:47 ` [PATCH v3 for-4.4] block: flush queued bios when process blocks to avoid deadlock Mike Snitzer
2015-10-14 21:44 ` Jeff Moyer
2015-10-17 16:04 ` Ming Lei
2015-10-20 19:57 ` Mike Snitzer
2015-10-20 20:03 ` Mikulas Patocka
2015-10-21 16:38 ` Ming Lei
2015-10-21 21:49 ` Mikulas Patocka
2015-10-22 1:53 ` Ming Lei
2015-10-15 3:27 ` [PATCH v2] block: flush queued bios when the process blocks Ming Lei
2015-10-15 8:06 ` Mike Snitzer
2015-10-16 3:08 ` Ming Lei
2015-10-16 15:29 ` Mike Snitzer
2015-10-17 15:54 ` Ming Lei
2015-10-09 11:58 ` kbuild test robot
2014-05-27 17:59 ` [PATCH] " Kent Overstreet
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