From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Dan Williams" Subject: Re: Kernel 2.6.19.2 New RAID 5 Bug (oops when writing Samba -> RAID5) Date: Mon, 22 Jan 2007 18:44:11 -0700 Message-ID: References: <45B5261B.1050104@redhat.com> <17845.13256.284461.992275@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <17845.13256.284461.992275@notabene.brown> Content-Disposition: inline Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: Chuck Ebbert , Justin Piszcz , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, xfs@oss.sgi.com List-Id: linux-raid.ids On 1/22/07, Neil Brown wrote: > On Monday January 22, cebbert@redhat.com wrote: > > Justin Piszcz wrote: > > > My .config is attached, please let me know if any other information is > > > needed and please CC (lkml) as I am not on the list, thanks! > > > > > > Running Kernel 2.6.19.2 on a MD RAID5 volume. Copying files over Samba to > > > the RAID5 running XFS. > > > > > > Any idea what happened here? > .... > > > > > Without digging too deeply, I'd say you've hit the same bug Sami Farin > > and others > > have reported starting with 2.6.19: pages mapped with kmap_atomic() > > become unmapped > > during memcpy() or similar operations. Try disabling preempt -- that > > seems to be the > > common factor. > > That is exactly the conclusion I had just come to (a kmap_atomic page > must be being unmapped during memcpy). I wasn't aware that others had > reported it - thanks for that. > > Turning off CONFIG_PREEMPT certainly seems like a good idea. > Coming from an ARM background I am not yet versed in the inner workings of kmap_atomic, but if you have time for a question I am curious as to why spin_lock(&sh->lock) is not sufficient pre-emption protection for copy_data() in this case? > NeilBrown Regards, Dan