linux-kernel - Re: [PATCH 1/2] shmem: fix init_page

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Message-ID: <20140630220033.GS10819@suse.de>
Date:	Mon, 30 Jun 2014 23:00:33 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] shmem: fix init_page_accessed use to stop !PageLRU
 bug

On Mon, Jun 30, 2014 at 02:08:11PM -0700, Hugh Dickins wrote:
> Under shmem swapping load, I sometimes hit the VM_BUG_ON_PAGE(!PageLRU)
> in isolate_lru_pages() at mm/vmscan.c:1281!
> 
> Commit 2457aec63745 ("mm: non-atomically mark page accessed during page
> cache allocation where possible") looks like interrupted work-in-progress.
> 
> mm/filemap.c's call to init_page_accessed() is fine, but not mm/shmem.c's
> - shmem_write_begin() is clearly wrong to use it after shmem_getpage(),
> when the page is always visible in radix_tree, and often already on LRU.
> 
> Revert change to shmem_write_begin(), and use init_page_accessed() or
> mark_page_accessed() appropriately for SGP_WRITE in shmem_getpage_gfp().
> 
> SGP_WRITE also covers shmem_symlink(), which did not mark_page_accessed()
> before; but since many other filesystems use [__]page_symlink(), which did
> and does mark the page accessed, consider this as rectifying an oversight.
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>

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

-- 
Mel Gorman
SUSE Labs
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