linux-kernel - Re: [PATCH] mm, fadvise: don't return -EINVAL when filesystem has no optimization way

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Date:	Wed, 20 Jun 2012 01:01:25 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hillf Danton <dhillf@...il.com>,
	Eric Wong <normalperson@...t.net>
Subject: Re: [PATCH] mm, fadvise: don't return -EINVAL when filesystem has no
 optimization way

On Fri, Jun 15, 2012 at 4:36 PM,  <kosaki.motohiro@...il.com> wrote:
> From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>
> Eric Wong reported his test suite was fail when /tmp is tmpfs.
>
> https://lkml.org/lkml/2012/2/24/479
>
> Current,input check of POSIX_FADV_WILLNEED has two problems.
>
> 1) require a_ops->readpage.
>   But in fact, force_page_cache_readahead() only require
>   a target filesystem has either ->readpage or ->readpages.
> 2) return -EINVAL when filesystem don't have ->readpage.
>   But, posix says, it should be retrieved a hint. Thus fadvise()
>   should return 0 if filesystem has no optimization way.
>   Especially, userland application don't know a filesystem type
>   of TMPDIR directory as Eric pointed out. Then, userland can't
>   avoid this error. We shouldn't encourage to ignore syscall
>   return value.
>
> Thus, this patch change a return value to 0 when filesytem don't
> support readahead.
>
> Cc: linux-mm@...ck.org
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Hillf Danton <dhillf@...il.com>
> Signed-off-by: Eric Wong <normalperson@...t.net>
> Tested-by: Eric Wong <normalperson@...t.net>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> ---

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