Re: RAID1 might_sleep() warning on 3.19-rc7

[Peter Zijlstra]

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@xxxxxxxxxxxxx> 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.
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