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Date: Tue, 16 Jul 2002 01:52:40 -0700
From: Andrew Morton <akpm@zip.com.au>
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To: Jens Axboe <axboe@suse.de>
CC: William Lee Irwin III <wli@holomorphy.com>, linux-kernel@vger.kernel.org
Subject: Re: [BUG] loop.c oopses
References: <20020716062453.GK1022@holomorphy.com> <3D33C64A.7491B591@zip.com.au> <20020716083142.GQ811@suse.de>
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Jens Axboe wrote:
> 
> On Tue, Jul 16 2002, Andrew Morton wrote:
> > William Lee Irwin III wrote:
> > >
> > > loop.c oopses when bio_copy() returns NULL. This was encountered while
> > > running dbench 16 on a loopback-mounted reiserfs filesystem.
> >
> > ugh.  GFP_NOIO is evil.  I guess it's better to add __GFP_HIGH
> > there, but it's not a happy solution.
> 
> GFP_NOIO has __GFP_WAIT set, so bio_copy -> bio_alloc -> mempool_alloc
> should never fail. Puzzled.
> 

Presumably the loop driver was called from within shrink_cache(),
as PF_MEMALLOC.  Those allocations can fail.

That's maybe wrong - if there are a decent number of pages
under writeback then we should be able to just wait it out.
But it gets tricky with the loop driver...

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