linux-kernel - Re: [PATCH 0/7] overlay filesystem v9

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Message-ID: <87ipt5vl7t.fsf@tucsk.pomaz.szeredi.hu>
Date:	Fri, 20 May 2011 10:18:30 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	NeilBrown <neilb@...e.de>
Cc:	Andy Whitcroft <apw@...onical.com>, viro@...IV.linux.org.uk,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, nbd@...nwrt.org, hramrach@...trum.cz,
	jordipujolp@...il.com
Subject: Re: [PATCH 0/7] overlay filesystem v9

(Neil, sorry for the dup)

NeilBrown <neilb@...e.de> writes:

> On Thu, 19 May 2011 19:05:58 +0100 Andy Whitcroft <apw@...onical.com> wrote:
>
>> On Thu, May 19, 2011 at 07:44:54PM +0200, Miklos Szeredi wrote:
>> > I'd be happier if the LSM module were fixed not to peek inside the inode
>> > structure.  Some filesystems (notably network ones) do not guarantee i_*
>> > to be up-to-date, relying on these is not a good idea.
>> 
>> I wonder what what the official way to get ownership information for an
>> inode is if we cannot rely on those.  I am happy to get the Yama LSM
>> fixed up if they are doing something wrong.
>> 
>> -apw
>
> inode->getattr(...., &kstat);
> look at kstat.uid, kstat.gid.

Yeah, it should probably do something like:

	if (inode->i_op->getattr) {
		struct kstat stat;
		inode->i_op->getattr(...)
		uid = stat.uid;
	} else {
		uid = inode->i_uid;
	}

The problem is that getattr takes a vfsmount, which makes this
impossible to do cleanly.  And the solution is for ->getattr() to lose
that argument, which is a bit more involved :(

Thanks,
Miklos
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