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

From:  Theodore Ts'o <tytso-3s7WtUTddSA-AT-public.gmane.org>
To:  "J. Bruce Fields" <bfields-uC3wQj2KruNg9hUCZPvPmw-AT-public.gmane.org>
Subject:  Re: [Gluster-devel] regressions due to 64-bit ext4 directory cookies
Date:  Wed, 13 Feb 2013 17:47:20 -0500
Message-ID:  <20130213224720.GE5938@thunk.org>
Cc:  Anand Avati <anand.avati-Re5JQEeQqe8AvxtiuMwx3w-AT-public.gmane.org>, Bernd Schubert <bernd.schubert-mPn0NPGs4xGatNDF+KUbs4QuADTiUCJX-AT-public.gmane.org>, sandeen-H+wXaHxf7aLQT0dZR+AlfA-AT-public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA-AT-public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA-AT-public.gmane.org, gluster-devel-qX2TKyscuCcdnm+yROfE0A-AT-public.gmane.org
Archive-link:  Article, Thread

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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