Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish_plug()

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Chris Mason <clm@fb.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Josef Bacik <jbacik@fb.com>, LKML <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Dave Chinner <david@fromorbit.com>, Neil Brown <neilb@suse.de>,
	Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish_plug()
Date: Sat, 12 Sep 2015 16:29:06 -0700	[thread overview]
Message-ID: <CA+55aFzbniZkd4EegyKqNmyXWQF6dPypvdovP4K7RdeBrdZDVg@mail.gmail.com> (raw)
In-Reply-To: <20150912230027.GE4150@ret.masoncoding.com>

On Sat, Sep 12, 2015 at 4:00 PM, Chris Mason <clm@fb.com> wrote:
>
> I did the plain revert as well, just to have a baseline.

Ahh, I ended up not expecting you to get this done until after rc1 was
out, so I in the meantime just merged my fix instead rather than leave
the expected scheduling-while-atomic problem.

And just as well that you did a baseline, since apparently the numbers
are all over the map. I don't see how your hack and dave's original
can _possibly_ differ that much, but they clearly did on your xfs
test. So there's probably huge variance that depends on random
details.

I'll leave things as they are until we have something that looks a bit
more believable ;)

               Linus