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Date: Wed, 7 Jul 2010 07:28:14 +0900
Message-ID: <AANLkTimOkI95ZkJecE3jxRDDGbHvP9tRUluIoJuhqqMz@mail.gmail.com>
Subject: Re: [PATCH 12/14] vmscan: Do not writeback pages in direct reclaim
From: Minchan Kim <minchan.kim@gmail.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
       Dave Chinner <david@fromorbit.com>,
       Chris Mason <chris.mason@oracle.com>, Nick Piggin <npiggin@suse.de>,
       Rik van Riel <riel@redhat.com>, Christoph Hellwig <hch@infradead.org>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Andrea Arcangeli <aarcange@redhat.com>
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On Wed, Jul 7, 2010 at 5:27 AM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> On Tue, Jul 06, 2010 at 04:25:39PM +0100, Mel Gorman wrote:
>> On Tue, Jul 06, 2010 at 08:24:57PM +0900, Minchan Kim wrote:
>> > but it is still problem in case of swap file.
>> > That's because swapout on swapfile cause file system writepage which
>> > makes kernel stack overflow.
>>
>> I don't *think* this is a problem unless I missed where writing out to
>> swap enters teh filesystem code. I'll double check.
>
> It bypasses the fs.  On swapon, the blocks are resolved
> (mm/swapfile.c::setup_swap_extents) and then the writeout path uses
> bios directly (mm/page_io.c::swap_writepage).
>
> (GFP_NOFS still includes __GFP_IO, so allows swapping)
>
>        Hannes

Thanks, Hannes. You're right.
Extents would be resolved by setup_swap_extents.
Sorry for confusing, Mel.

It was just my guessing about Kosaki's mention but he might say another story.
Ignore me.

-- 
Kind regards,
Minchan Kim
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