linux-ext4 - Re: [Gluster-devel] regressions due to 64-bit ext4 directory cookies

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Date:	Wed, 13 Feb 2013 17:47:20 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Anand Avati <anand.avati@...il.com>,
	Bernd Schubert <bernd.schubert@...m.fraunhofer.de>,
	sandeen@...hat.com, linux-nfs@...r.kernel.org,
	linux-ext4@...r.kernel.org, gluster-devel@...gnu.org
Subject: Re: [Gluster-devel] regressions due to 64-bit ext4 directory cookies

On Wed, Feb 13, 2013 at 05:41:41PM -0500, J. Bruce Fields wrote:
> > What if we have an ioctl or a process personality flag where a broken
> > application can tell the file system "I'm broken, please give me a
> > degraded telldir/seekdir cookie"?  That way we don't penalize programs
> > that are doing the right thing, while providing some accomodation for
> > programs who are abusing the telldir cookie.
> 
> Yeah, if there's a simple way to do that, maybe it would be worth it.

Doing this as an ioctl which gets called right after opendir, i.e
(ignoring error checking):

      DIR *dir = opendir("/foo/bar/baz");
      ioctl(dirfd(dir), EXT4_IOC_DEGRADED_READDIR, 1);
      ...

should be quite easy.  It would be a very ext3/4 specific thing,
though.

It would be more work to get something in as a process personality
flag, mostly due to the politics of assiging a bit out of the
bitfield.

						- Ted

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