linux-kernel - Re: [rfc] new stat*fs-like syscall?

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Message-ID: <4C24319F.1030307@garzik.org>
Date:	Fri, 25 Jun 2010 00:33:35 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Nick Piggin <npiggin@...e.de>
CC:	Andreas Dilger <adilger@...ger.ca>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [rfc] new stat*fs-like syscall?

On 06/25/2010 12:01 AM, Nick Piggin wrote:
> So is "frsize" supposed to be the optimal block size, or what?
> f_bsize AFAIKS should be filesystem allocation block size because
> apparently some programs require it to calculate size of file on
> disk.
>
> If we can't change existing suboptimal legacy things, then let's
> introduce new APIs that do the right thing. Apps that care will
> eventually start using eg. a new syscall.
>
>>
>>> - statvfs(2) lacks f_type.
>>>
>>> Is there anything more we should add here? Samba wants a capabilities
>>> field, with things like sparse files, quotas, compression, encryption,
>>> case preserving/sensitive.
>>
>> It wouldn't be a bad idea, but then you could get into issues of what exactly the above flags mean.  That said, I think it is better to have broad categories of features that may be slightly ill-defined than having nothing at all.
>
> Yes it would be tricky. I don't want to add features that will just
> be useless or go unused, but I don't want to change the syscall API
> just to add f_flags, without looking at other possibilities.


It would be nice to separate capabilities and fixed parameters (block 
size) from statistics which change frequently (free space).

And are capabilities really suited to a C struct, at all?  That seems 
more suited to a key/value type interface, a la NFSv4 attributes.

	Jeff



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