linux-kernel - Re: [PATCH 14/38] fallthru: ext2 fallthru support

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Message-ID: <20100808164045.GA17549@shell>
Date:	Sun, 8 Aug 2010 12:40:45 -0400
From:	Valerie Aurora <vaurora@...hat.com>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	Miklos Szeredi <miklos@...redi.hu>,
	Jan Blunck <jblunck@...e.de>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Theodore Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 14/38] fallthru: ext2 fallthru support

On Fri, Aug 06, 2010 at 06:28:29PM -0600, Andreas Dilger wrote:
> On 2010-08-06, at 16:35, Valerie Aurora wrote:
> > XXX What to do for d_ino for fallthrus?  If we return the inode from
> > the the underlying file system, it comes from a different inode
> > "namespace" and that will produce spurious matches.  This argues for
> > implementation of fallthrus as symlinks because they have to allocate
> > an inode (and inode number) anyway, and we can later reuse it if we
> > copy the file up.
> > 
> > @@ -342,6 +344,24 @@ ext2_readdir (struct file * filp, void * dirent, +				/* XXX We don't know the inode number
> > +				 * of the directory entry in the
> > +				 * underlying file system.  Should
> > +				 * look it up, either on fallthru
> > +				 * creation at first readdir or now at
> > +				 * filldir time. */
> > +				over = filldir(dirent, de->name, de->name_len,
> > +					       (n<<PAGE_CACHE_SHIFT) | offset,
> > +					       123 /* Made up ino */, d_type);
> 
> I don't think it makes sense to use "123" for the inode number.  This is a valid inode number, and almost certainly one that will be in use in most filesystems.  One option for extN is to use EXT2_BAD_INO (1).

The next version (Subject: Union mounts - return d_ino from lower fs)
fixed this.  Take a look and tell me what you think?

-VAL
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