linux-kernel - Re: [PATCH] COMPACTION: bugfix of improper cache flush in MIGRATION code.

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Date:	Fri, 10 May 2013 10:52:12 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
Cc:	riel@...hat.com, mhocko@...e.cz, akpm@...ux-foundation.org,
	kamezawa.hiroyu@...fujitsu.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] COMPACTION: bugfix of improper cache flush in MIGRATION
 code.

On Wed, May 08, 2013 at 05:18:21PM -0700, Leonid Yegoshin wrote:
> Page 'new' during MIGRATION can't be flushed by flush_cache_page().
> Using flush_cache_page(vma, addr, pfn) is justified only if
> page is already placed in process page table, and that is done right
> after flush_cache_page(). But without it the arch function has
> no knowledge of process PTE and does nothing.
> 
> Besides that, flush_cache_page() flushes an application cache,
> kernel has a different page virtual address and dirtied it.
> 
> Replace it with flush_dcache_page(new) which is a proper usage.
> 
> Old page is flushed in try_to_unmap_one() before MIGRATION.
> 
> This bug takes place in Sead3 board with M14Kc MIPS CPU without
> cache aliasing (but Harvard arch - separate I and D cache)
> in tight memory environment (128MB) each 1-3days on SOAK test.
> It fails in cc1 during kernel build (SIGILL, SIGBUS, SIGSEG) if
> CONFIG_COMPACTION is switched ON.
> 
> Author: Leonid Yegoshin <yegoshin@...s.com>
> Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@...tec.com>

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs
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