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

From: Miklos Szeredi <miklos@szeredi.hu>
To: Andy Lutomirski <luto@mit.edu>
Cc: npiggin@suse.de, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, viro@ZenIV.linux.org.uk,
	drepper@redhat.com, torvalds@linux-foundation.org
Subject: Re: [rfc] new stat*fs-like syscall?
Date: Thu, 24 Jun 2010 16:18:58 +0200	[thread overview]
Message-ID: <E1ORnGc-0008CL-Uo@pomaz-ex.szeredi.hu> (raw)
In-Reply-To: <4C2366F7.5010200@mit.edu> (message from Andy Lutomirski on Thu, 24 Jun 2010 10:08:55 -0400)

On Thu, 24 Jun 2010, Andy Lutomirski wrote:
> Something like fsid but actually specified to uniquely identify a 
> superblock.  (Currently, fsid seems to be set by the filesystem, and 
> nothing in particular ensures that two different filesystems couldn't 
> have collisions.)  We could guarantee (or have a flag guaranteeing) that 
> (fsid, st_inode) actually uniquely identifies an inode.
> 
> Similarly, something like fsid that uniquely identifies the vfsmount 
> could be useful, although I don't know how easy that would be to provide 
> for fstat?fs.
> 
> If we could expose the complete set of filesystem mount options so that 
> mount(1) didn't have to look at /proc/self/mounts or /etc/mtab, then 
> playing with chroots would be that much easier.
> 
> Should we expose superblock and vfsmount options separately?  We have 
> read-only bind mounts now, but the way they work is rather inscrutable, 
> and if stat?fs could say "superblock is read-write but vfsmount is 
> readonly" then people might be able to make more sense of what's going on.

You'll find all of those things in /proc/self/mountinfo.

Thanks,
Miklos