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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Mon, 13 Feb 2012 11:22:26 -0500
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Subject: Re: [PATCH v5 3/3] fadvise: implement POSIX_FADV_NOREUSE
To: Andrea Righi <andrea@betterlinux.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Minchan Kim <minchan.kim@gmail.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
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> @@ -1181,8 +1258,22 @@ page_ok:
> ? ? ? ? ? ? ? ? * When a sequential read accesses a page several times,
> ? ? ? ? ? ? ? ? * only mark it as accessed the first time.
> ? ? ? ? ? ? ? ? */
> - ? ? ? ? ? ? ? if (prev_index != index || offset != prev_offset)
> - ? ? ? ? ? ? ? ? ? ? ? mark_page_accessed(page);
> + ? ? ? ? ? ? ? if (prev_index != index || offset != prev_offset) {
> + ? ? ? ? ? ? ? ? ? ? ? int mode;
> +
> + ? ? ? ? ? ? ? ? ? ? ? mode = filemap_get_cache(mapping, index);
> + ? ? ? ? ? ? ? ? ? ? ? switch (mode) {
> + ? ? ? ? ? ? ? ? ? ? ? case FILEMAP_CACHE_NORMAL:
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? mark_page_accessed(page);
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? break;
> + ? ? ? ? ? ? ? ? ? ? ? case FILEMAP_CACHE_ONCE:
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? mark_page_usedonce(page);
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? break;
> + ? ? ? ? ? ? ? ? ? ? ? default:
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? WARN_ON_ONCE(1);
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? break;

Here is generic_file_read, right? Why don't you care write and page fault?
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