From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [WTF] ... is going on with current->fs->{root,mnt} accesses in
 pohmelfs
Date: Wed, 10 Feb 2010 21:02:48 +0000
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 <20100210104515.GA6207@ioremap.net>
 <20100210110011.GN30031@ZenIV.linux.org.uk>
 <20100210111115.GA8376@ioremap.net>
 <20100210115938.GO30031@ZenIV.linux.org.uk>
 <20100210133007.GA17744@ioremap.net>
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Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
To: Evgeniy Polyakov <zbr@ioremap.net>
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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?