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Date: Wed, 23 Nov 2011 11:06:57 +0200
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Subject: Re: [V3 PATCH 1/2] tmpfs: add fallocate support
From: Pekka Enberg <penberg@kernel.org>
To: Cong Wang <amwang@redhat.com>
Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        Christoph Hellwig <hch@lst.de>, Hugh Dickins <hughd@google.com>,
        Dave Hansen <dave@linux.vnet.ibm.com>,
        Lennart Poettering <lennart@poettering.net>,
        Kay Sievers <kay.sievers@vrfy.org>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, linux-mm@kvack.org
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On Wed, Nov 23, 2011 at 10:53 AM, Cong Wang <amwang@redhat.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@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Dave Hansen <dave@linux.vnet.ibm.com>
> Cc: Lennart Poettering <lennart@poettering.net>
> Cc: Kay Sievers <kay.sievers@vrfy.org>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: WANG Cong <amwang@redhat.com>

Looks reasonable to me.

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

Did someone actually test this with systemd?