From: Theodore Ts'o Subject: Re: [PATCH] Remove ext4 xattr mbcache to fix CPU lockup when using ceph #107301 Date: Fri, 20 Nov 2015 23:22:08 -0500 Message-ID: <20151121042208.GC350@thunk.org> References: <1448012628.1905.253.camel@guerby.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Laurent GUERBY , Jan Kara , "linux-ext4@vger.kernel.org" , "sage@redhat.com" , Abaakouk Mehdi , Loic Dachary To: Andreas Dilger Return-path: Received: from imap.thunk.org ([74.207.234.97]:44061 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751666AbbKUEWa (ORCPT ); Fri, 20 Nov 2015 23:22:30 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Nov 20, 2015 at 06:08:15PM -0700, Andreas Dilger wrote: > > I'm definitely not in favor of deleting mbcache entirely, just having the > mount option to disable it in cases where it is known not to be useful, > such as Ceph or Lustre backing stores that never have shared xattrs. > > In some cases mbcache can be useful, since it allows sharing xattrs > between inodes. > > I thought you would update our patch to add the mount option to disable > mbcache? And better yet would be if there was a blacklist of Lustre and Ceph xattr type/keys that will never have shared attrs, so that mbcache is not used for those xattrs automatically, *without* using a mount option. Can someone at least start help creating that list? But yeah, a complete deletion of mbcache is a non-starter. Regards, - Ted