linux-kernel - Re: [patch 0/15] LogFS take five

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Date:	Fri, 4 Apr 2008 13:46:00 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	joern@...fs.org
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mtd@...ts.infradead.org, Nick Piggin <npiggin@...e.de>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [patch 0/15] LogFS take five

On Tue, Apr 01 2008, joern@...fs.org wrote:
> And it is currently reasonably simple to run into a deadlock when
> using logfs on a block device.  The problem appears to be the block
> layer allocating memory for its cache without GFP_NOFS, so that under
> memory pressure logfs writes through block layer may recurse back to
> logfs writes.

So you mean for writes through the page cache, you are seeing pages
allocated with __GFP_FS set?

> Not entirely sure who is to blame for this bug and how to
> solve it.

A good starting point would be doing a stack trace dump in logfs if you
see such back recursion into the fs. A quick guess would be a missing
setting of mapping gfp mask?

-- 
Jens Axboe

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