linux-kernel - Re: [V3 PATCH 1/2] tmpfs: add fallocate support

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Date:	Wed, 23 Nov 2011 11:06:57 +0200
From:	Pekka Enberg <penberg@...nel.org>
To:	Cong Wang <amwang@...hat.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Christoph Hellwig <hch@....de>,
	Hugh Dickins <hughd@...gle.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Lennart Poettering <lennart@...ttering.net>,
	Kay Sievers <kay.sievers@...y.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-mm@...ck.org
Subject: Re: [V3 PATCH 1/2] tmpfs: add fallocate support

On Wed, Nov 23, 2011 at 10:53 AM, Cong Wang <amwang@...hat.com> wrote:
> Systemd needs tmpfs to support fallocate [1], to be able
> to safely use mmap(), regarding SIGBUS, on files on the
> /dev/shm filesystem. The glibc fallback loop for -ENOSYS
> on fallocate is just ugly.
>
> This patch adds fallocate support to tmpfs, and as we
> already have shmem_truncate_range(), it is also easy to
> add FALLOC_FL_PUNCH_HOLE support too.
>
> 1. http://lkml.org/lkml/2011/10/20/275
>
> V2->V3:
> a) Read i_size directly after holding i_mutex;
> b) Call page_cache_release() too after shmem_getpage();
> c) Undo previous changes when -ENOSPC.
>
> Cc: Pekka Enberg <penberg@...nel.org>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Dave Hansen <dave@...ux.vnet.ibm.com>
> Cc: Lennart Poettering <lennart@...ttering.net>
> Cc: Kay Sievers <kay.sievers@...y.org>
> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Signed-off-by: WANG Cong <amwang@...hat.com>

Looks reasonable to me.

Acked-by: Pekka Enberg <penberg@...nel.org>

Did someone actually test this with systemd?
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