linux-kernel - Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish

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Message-ID: <CA+55aFwx3sXm_79qyk2z-YoGx491ra-XMvAc3T-hifHpD72HZg@mail.gmail.com>
Date:	Thu, 17 Sep 2015 16:13:56 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Chinner <david@...morbit.com>
Cc:	Chris Mason <clm@...com>, Jan Kara <jack@...e.cz>,
	Josef Bacik <jbacik@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Neil Brown <neilb@...e.de>, Christoph Hellwig <hch@....de>,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish_plug()

On Thu, Sep 17, 2015 at 4:03 PM, Dave Chinner <david@...morbit.com> wrote:
>
> Ok, I'm happy to report there is actually nothing wrong with the
> plugging code that is your tree.  I finally tracked the problem I
> was seeing down to a misbehaving RAID controller.[*]

Hey, that's great.

Just out of interest, try the patch that Chris just sent that turns
the unplugging synchronous for the special "cond_resched()" case.

If that helps your case too, let's just do it, even while we wonder
why kblockd_workqueue messes up so noticeable.

Because regardless of the kblockd_workqueue questions, I think it's
nicer to avoid the cond_resched_lock(), and do the rescheduling while
we're not holding any locks.

              Linus
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