From: Mike Snitzer <snitzer@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
Bart Van Assche <bvanassche@acm.org>,
Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH v3] blk-mq: punt failed direct issue to dispatch list
Date: Fri, 7 Dec 2018 10:15:08 -0500 [thread overview]
Message-ID: <20181207151507.GA20544@redhat.com> (raw)
In-Reply-To: <aa6abfa7-30c3-57d7-7369-754d514584f5@kernel.dk>
On Fri, Dec 07 2018 at 12:17am -0500,
Jens Axboe <axboe@kernel.dk> wrote:
> After the direct dispatch corruption fix, we permanently disallow direct
> dispatch of non read/write requests. This works fine off the normal IO
> path, as they will be retried like any other failed direct dispatch
> request. But for the blk_insert_cloned_request() that only DM uses to
> bypass the bottom level scheduler, we always first attempt direct
> dispatch. For some types of requests, that's now a permanent failure,
> and no amount of retrying will make that succeed. This results in a
> livelock.
>
> Instead of making special cases for what we can direct issue, and now
> having to deal with DM solving the livelock while still retaining a BUSY
> condition feedback loop, always just add a request that has been through
> ->queue_rq() to the hardware queue dispatch list. These are safe to use
> as no merging can take place there. Additionally, if requests do have
> prepped data from drivers, we aren't dependent on them not sharing space
> in the request structure to safely add them to the IO scheduler lists.
>
> This basically reverts ffe81d45322c and is based on a patch from Ming,
> but with the list insert case covered as well.
>
> Fixes: ffe81d45322c ("blk-mq: fix corruption with direct issue")
> Cc: stable@vger.kernel.org
> Suggested-by: Ming Lei <ming.lei@redhat.com>
> Reported-by: Bart Van Assche <bvanassche@acm.org>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Looks good, thanks!
Acked-by: Mike Snitzer <snitzer@redhat.com>
next prev parent reply other threads:[~2018-12-07 15:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-07 5:17 [PATCH v3] blk-mq: punt failed direct issue to dispatch list Jens Axboe
2018-12-07 8:24 ` Ming Lei
2018-12-07 10:50 ` Ming Lei
2018-12-07 15:15 ` Mike Snitzer [this message]
2018-12-07 16:19 ` Bart Van Assche
2018-12-07 16:24 ` Jens Axboe
2018-12-07 16:35 ` Jens Axboe
2018-12-07 16:41 ` Bart Van Assche
2018-12-07 16:45 ` Jens Axboe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181207151507.GA20544@redhat.com \
--to=snitzer@redhat.com \
--cc=axboe@kernel.dk \
--cc=bvanassche@acm.org \
--cc=linux-block@vger.kernel.org \
--cc=ming.lei@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).