linux-kernel - Re: [WTF] ... is going on with current->fs->{root,mnt} accesses in pohmelfs

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Date:	Wed, 10 Feb 2010 16:30:07 +0300
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [WTF] ... is going on with current->fs->{root,mnt} accesses in pohmelfs

On Wed, Feb 10, 2010 at 11:59:39AM +0000, Al Viro (viro@...IV.linux.org.uk) wrote:
> > Let me guess... Mmmm, it was in the yesterday newspaper, I remember.
> > Maybe when we chroot somewhere. I meant not mounted fs root, but
> > thread's root.
> 
> Why would a filesystem give a damn about the chroot of syscall originator
> in the first place?

That's the point - it is not needed.

> > > Why not use the dentries you've been given by VFS?
> > 
> > At writeback we do not have parents, so must find a path somehow.
> 
> Most of the places do have those just fine and unlike the writeback,
> rename et.al. really care which pathname is being dealt with...

POHMELFS uses writeback cache also for metadata, so effectively most of
such operations are also postponed. Later I turned that off though.

> BTW, what prevents writeback vs. rename races?

There are proper locks for such operations.

-- 
	Evgeniy Polyakov
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