Re: Bugs / Patch in nfsd

[Christoph Hellwig <hch@infradead.org>]

On Mon, Nov 18, 2013 at 12:37:31PM -0500, J. Bruce Fields wrote:
> One problem he's seeing was RHEL5-specific, the other is the known ext4
> problem that's been discussed before.

Ok, didn't know there was a RHEL bug.

> (Basically, ext4 has a tradeoff between correctness, lookup performance,
> and compatibility with some buggy old clients:
> 
> 	1. turn off dir_index and performance on large directories may
> 	   suffer, but it's correct and any client will be happy.
> 	2. turn on dir_index and return 32-bit cookies: now you get
> 	   directory loops on large directories due to random hash
> 	   collisions.
> 	3. turn on dir_index and return 64-bit cookies: some clients seem
> 	   to then return errors to 32-bit applications doing readdirs.
> 	   Cookies have been 64-bit since NFSv3 and 32-bit Linux clients
> 	   deal with this fine (it fakes up its own small integer offsets
> 	   to return to applications), but apparently some other clients
> 	   return errors on readdir.
> 
> So currently we default to 3 and if people complain, tell them to turn
> off dir_index and complain to their client vendor....)

Or people could use a filesystem taking care of that.  In addition to
taking care of the directory index XFS also has other advantages like
much better support to get the metadata operations to disk a lot more
efficiently.


... working hard on my marketing skills..