linux-ext4 - Re: [patch 1/5] mm: add nofail variants of kmalloc kcalloc and kzalloc

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Message-ID: <20100824135522.GK31488@dastard>
Date:	Tue, 24 Aug 2010 23:55:22 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Neil Brown <neilb@...e.de>, Alasdair G Kergon <agk@...hat.com>,
	Chris Mason <chris.mason@...cle.com>,
	Steven Whitehouse <swhiteho@...hat.com>,
	Jens Axboe <jaxboe@...ionio.com>, Jan Kara <jack@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-raid@...r.kernel.org, linux-btrfs@...r.kernel.org,
	cluster-devel@...hat.com, linux-ext4@...r.kernel.org,
	reiserfs-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/5] mm: add nofail variants of kmalloc kcalloc and
 kzalloc

On Tue, Aug 24, 2010 at 03:29:18PM +0200, Peter Zijlstra wrote:
> On Tue, 2010-08-24 at 03:50 -0700, David Rientjes wrote:
> > These were added as helper functions for documentation and auditability.
> > No future callers should be added.
> 
> git grep GFP_NOFAIL isn't auditable enough?
> 
> might as well declare these functions depricated if you really want to
> do this.

Also, if you are going to add tight loops, you might want to put a
backoff in the loops like "congestion_wait(BLK_RW_ASYNC, HZ/50);" so
that they don't spin....

FWIW, in all this "allocations can't fail" churn, no one has noticed
that XFS has been doing these "allocations can't fail" loop in
kmem_alloc() and kmem_zone_alloc(), well, forever. I can't ever
remember seeing it report a potential deadlock, though....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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