Re: [V2 PATCH] tmpfs: add fallocate support

[Kay Sievers]

On Sat, Nov 19, 2011 at 11:03, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> On Fri, Nov 18, 2011 at 06:39:50PM +0800, Cong Wang wrote:
>> It seems that systemd needs tmpfs to support fallocate,
>> see http://lkml.org/lkml/2011/10/20/275. This patch adds
>> fallocate support to tmpfs.
>
> What for exactly? ÂPlease explain why preallocating on tmpfs would
> make any sense.

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.

Kay
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