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

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Message-ID: <20100210210248.GP30031@ZenIV.linux.org.uk>
Date:	Wed, 10 Feb 2010 21:02:48 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Evgeniy Polyakov <zbr@...emap.net>
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 04:30:07PM +0300, Evgeniy Polyakov wrote:
> > > > 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.

Which would be... ?  E.g. between writepages() and rename().  What serializes
your write_inode_create() wrt renames?  IOW, how can the server decide that
data from writepages() should go to the same object regardless of the
rename?
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