Re: [V2 PATCH] tmpfs: add fallocate support

[Cong Wang <amwang@redhat.com>]

ao? 2011a1'11ae??21ae?JPY 05:22, Hugh Dickins a??e??:
> On Fri, 18 Nov 2011, 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.
>>
>> As we already have shmem_truncate_range(), it is also easy
>> to add FALLOC_FL_PUNCH_HOLE support too.
>
> Thank you, this version looks much much nicer.
>
> I wouldn't call it bug-free (don't you need a page_cache_release
> after the unlock_page?), and I won't be reviewing it and testing it
> for a week or two - there's a lot about the semantics of fallocate
> and punch-hole that's not obvious, and I'll have to study the mail
> threads discussing them before checking your patch.

Yeah, sorry, I missed unlock_page()...

>
> First question that springs to mind (to which I shall easily find
> an answer): is it actually acceptable for fallocate() to return
> -ENOSPC when it has already completed a part of the work?

Ah, good point, I will fix this as what Christoph suggested.

>
> But so long as the details don't end up complicating this
> significantly, since we anyway want to regularize the punch-hole
> situation by giving tmpfs the same interface to it as other filesystems,
> I now think it would be a bit perverse to disallow the original
> fallocate functionality that you implement here in-kernel.
>

Ok, I think you mean you are fine to accept it now?

Anyway, thanks a lot for your comments!

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