From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: RAID1 might_sleep() warning on 3.19-rc7
Date: Tue, 10 Feb 2015 12:01:16 +0100
Message-ID: <20150210110116.GP24151@twins.programming.kicks-ass.net>
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To: NeilBrown <neilb@suse.de>
Cc: Tony Battersby <tonyb@cybernetics.com>, linux-raid@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>, axboe@kernel.dk, Linus Torvalds <torvalds@linux-foundation.org>
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On Tue, Feb 10, 2015 at 10:29:36AM +0100, Peter Zijlstra wrote:
> On Tue, Feb 10, 2015 at 01:50:17PM +1100, NeilBrown wrote:
> > On Mon, 9 Feb 2015 10:10:00 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> > > > However, when io_schedule() explicitly calls blk_flush_plug(), then
> > > > @from_schedule=false variant is used, and the unplug functions are allowed to
> > > > allocate memory and block and maybe even call mempool_alloc() which might
> > > > call io_schedule().

Note that as it stands recursively calling io_schedule() is already
broken. Things like delayacct_blkio_{start,end}() do not nest properly.