linux-kernel - Re: [PATCH] mm: fix page-faults detection in swap-token logic

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Message-Id: <20110829160637.bfc86e63.akpm@linux-foundation.org>
Date:	Mon, 29 Aug 2011 16:06:37 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH] mm: fix page-faults detection in swap-token logic

On Sat, 27 Aug 2011 12:32:01 +0300
Konstantin Khlebnikov <khlebnikov@...nvz.org> wrote:

> After commit v2.6.36-5896-gd065bd8 "mm: retry page fault when blocking on disk transfer"
> we usually wait in page-faults without mmap_sem held, so all swap-token logic was broken,
> because it based on using rwsem_is_locked(&mm->mmap_sem) as sign of in progress page-faults.

If I'm interpreting this correctly, the thrash-handling logic has been
effectively disabled for a year and nobody noticed.

> This patch adds to mm_struct atomic counter of in progress page-faults for mm with swap-token.

We desperately need to delete some code from mm/.  This seems like a
great candidate.  Someone prove me wrong?
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