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

From: Jeff Garzik <jeff@garzik.org>
To: Nick Piggin <npiggin@suse.de>
Cc: Andreas Dilger <adilger@dilger.ca>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Al Viro <viro@ZenIV.linux.org.uk>,
	Ulrich Drepper <drepper@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [rfc] new stat*fs-like syscall?
Date: Fri, 25 Jun 2010 00:33:35 -0400	[thread overview]
Message-ID: <4C24319F.1030307@garzik.org> (raw)
In-Reply-To: <20100625040156.GQ10441@laptop>

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