linux-kernel - Re: [Patch] tmpfs: add fallocate support

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Date:	Wed, 16 Nov 2011 15:09:52 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Pekka Enberg <penberg@...nel.org>
CC:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	kay.sievers@...y.org
Subject: Re: [Patch] tmpfs: add fallocate support

于 2011年11月15日 19:23, Pekka Enberg 写道:
> Hello,
>
> On Tue, Nov 15, 2011 at 10:42 AM, Amerigo Wang<amwang@...hat.com>  wrote:
>> This patch adds fallocate support to tmpfs. I tested this patch
>> with the following test case,
>>
>>         % sudo mount -t tmpfs -o size=100 tmpfs /mnt
>>         % touch /mnt/foobar
>>         % echo hi>  /mnt/foobar
>>         % fallocate -o 3 -l 5000 /mnt/foobar
>>         fallocate: /mnt/foobar: fallocate failed: No space left on device
>>         % fallocate -o 3 -l 3000 /mnt/foobar
>>         % ls -l /mnt/foobar
>>         -rw-rw-r-- 1 wangcong wangcong 3003 Nov 15 16:10 /mnt/foobar
>>         % dd if=/dev/zero of=/mnt/foobar seek=3 bs=1 count=3000
>>         3000+0 records in
>>         3000+0 records out
>>         3000 bytes (3.0 kB) copied, 0.0153224 s, 196 kB/s
>>         % hexdump -C /mnt/foobar
>>         00000000  68 69 0a 00 00 00 00 00  00 00 00 00 00 00 00 00  |hi..............|
>>         00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
>>         *
>>         00000bb0  00 00 00 00 00 00 00 00  00 00 00                 |...........|
>>         00000bbb
>>         % cat /mnt/foobar
>>         hi
>>
>> Signed-off-by: WANG Cong<amwang@...hat.com>
>
> What's the use case for this?
>

Hi, Pekka,

Systemd needs it, see http://lkml.org/lkml/2011/10/20/275.
I am adding Kay into Cc.

Thanks.
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