linux-ext4 - Re: [PATCH 13/35] fallthru: ext2 fallthru support

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Date:	Mon, 19 Apr 2010 15:23:44 +0200
From:	Jan Blunck <jblunck@...e.de>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Valerie Aurora <vaurora@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Theodore Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 13/35] fallthru: ext2 fallthru support

On Mon, Apr 19, David Woodhouse wrote:

> On Mon, 2010-04-19 at 14:40 +0200, Jan Blunck wrote:
> > On Thu, Apr 15, Valerie Aurora wrote:
> > 
> > > Add support for fallthru directory entries to ext2.
> > > 
> > > XXX - Makes up inode number for fallthru entry
> > > XXX - Might be better implemented as special symlinks
> > 
> > Better not. David Woodhouse actually convinced me of moving away from the
> > special symlink approach. The whiteouts have been implemented as special
> > symlinks before.
> 
> I certainly asked whether you really need a real 'struct inode' for
> whiteouts, and suggested that they should be represented _purely_ as a
> dentry with type DT_WHT.
> 
> I don't much like the manifestation of that in this patch though,
> especially with the made-up inode number. (ISTR I had other
> jffs2-specific objections too, which I'll dig out and forward).

Yes, this patches still have issues that Val and me are aware off. I can't
remember anything jffs2-specific though.

We return that inode number because we don't want to lookup the name on the
other filesystem during readdir. Therefore returning DT_UNKNOWN to let the
userspace decide if it needs to stat the file was the easiest workaround. I
know that POSIX requires d_ino and d_name but on the other hand it does not
require anything more on how long d_ino is valid.

If somebody has an idea how to make this cleaner please speak up.

Regards,
	Jan

-- 
Jan Blunck <jblunck@...e.de>
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