From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH] Handle multipath paths in a path group properly during pg_init Date: Tue, 31 Mar 2009 08:33:35 +0200 Message-ID: <49D1B93F.6020900@suse.de> References: <1238436452.5858.2.camel@chandra-ubuntu> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <1238436452.5858.2.camel@chandra-ubuntu> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: sekharan@linux.vnet.ibm.com Cc: Mike Anderson , dm-devel , Alasdair G Kergon , "Moger, Babu" List-Id: dm-devel.ids Chandra Seetharaman wrote: > Resending the patch to get in patchwork... > ------- > The problem reported by Moger Babu was caused due to the architectural > change made when we moved from dm hardware handler to SCSI hardware > handler. >=20 > Thanks Babu for finding and reporting the bug. >=20 > All of the hardware handlers, do have a state now, and they are set to > active and (some form of) inactive. All of them have prep_fn, which use > this "state" to fail the I/O without it ever being sent to the device. >=20 > As Babu has noted in his email, the pg_init/activate is sent on only on= e > path and the "state" of that path is changed appropriately to "active" > while other paths in the same path group are never changed as they neve= r > got an "activate". >=20 > Attached is a patch (compiled, tested, but not clean yet), which makes > changes in the dm-multipath layer to send an "activate" on each paths i= n > the path groups. >=20 > Mike (Anderson) and I had a discussion about whether to implement this > in the dm-mulitpath layer or in the SCSI hardware handler layer and we > came to a conclusion that it is best suited to be in the dm-mulitpath > layer as it is the one that knows the relationship between different > paths. >=20 > If it were to be done at the Hardware handler layer, then the hardware > handler may end up having a different notion of the path relationship > and hence may not work as expected by the dm-multipath layer. >=20 > This patch has been tested by Hannes in EMC storage. Babu and I tested = it > in LSI storage. > ---------- >=20 > Signed-off-by: Chandra Seetharaman >=20 Acked-by: Hannes Reinecke Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: Markus Rex, HRB 16746 (AG N=FCrnberg)