linux-ext4 - Re: [RFC]jbd2: use GFP_NOFS for blkdev_issue

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Message-ID: <20120415224427.GV6734@dastard>
Date:	Mon, 16 Apr 2012 08:44:27 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Shaohua Li <shli@...nel.org>
Cc:	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tytso@....edu
Subject: Re: [RFC]jbd2: use GFP_NOFS for blkdev_issue_flush

On Fri, Apr 13, 2012 at 10:27:35AM +0800, Shaohua Li wrote:
> 
> flush request is issued in transaction commit code path, so looks using
> GFP_KERNEL to allocate memory for flush request bio falls into the classic
> deadlock issue.  I saw btrfs and dm get it right, but ext4, xfs and md are
> using GFP_KERNEL, which makes me confused. Hoping filesystem developers
> clarify.

Only one of the 5 calls XFS makes to blkdev_issue_flush() is
questionable. Probably should use GFP_NOFS by default, though, so we
don't trip over this problem...

Cheers,

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