linux-kernel - Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim and use a

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Message-ID: <4C17D0C5.9030203@redhat.com>
Date:	Tue, 15 Jun 2010 15:13:09 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
CC:	Andrea Arcangeli <aarcange@...hat.com>, Mel Gorman <mel@....ul.ie>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim
 and use a_ops->writepages() where possible

On 06/15/2010 12:54 PM, Christoph Hellwig wrote:
> On Tue, Jun 15, 2010 at 12:49:49PM -0400, Rik van Riel wrote:
>> This is already in a filesystem.  Why does ->writepage get
>> called a second time?  Shouldn't this have a gfp_mask
>> without __GFP_FS set?
>
> Why would it?  GFP_NOFS is not for all filesystem code, but only for
> code where we can't re-enter the filesystem due to deadlock potential.

Why?   How about because you know the stack is not big enough
to have the XFS call path on it twice? :)

Isn't the whole purpose of this patch series to prevent writepage
from being called by the VM, when invoked from a deep callstack
like xfs writepage?

That sounds a lot like simply wanting to not have GFP_FS...

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