linux-kernel - Re: RAID1 might_sleep() warning on 3.19-rc7

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Message-ID: <20150213102746.GO2896@worktop.programming.kicks-ass.net>
Date:	Fri, 13 Feb 2015 11:27:46 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	NeilBrown <neilb@...e.de>
Cc:	Tony Battersby <tonyb@...ernetics.com>, linux-raid@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>, axboe@...nel.dk,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: RAID1 might_sleep() warning on 3.19-rc7

On Fri, Feb 13, 2015 at 07:49:53PM +1100, NeilBrown wrote:
> > Like said, that will still recursive call delayacct_blkio_*() and would
> > increase nr_iowait for a second time; while arguably its still the same
> > one io-wait instance.
> 
> No it doesn't.  There is no "blk_flush_plug" call between the
> delayacct_blkio_*() calls.

Duh, clearly I needed to still wake up :/

> I've moved blk_flush_plug to the beginning of the function.

> I wondered if it really make sense to call blk_flush_plug with nr_iowait
> elevated and delayacct_blkio active.  blk_flush_plug() could call schedule()
> for non-"io" reasons and maybe that could upset stuff???

Yeah, good question that. Lemme ponder that a bit.

> I don't really know.  I'm happy with your version.  I don't suppose anyone
> else is paying attention and could give a third opinion....

:-)
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