From mboxrd@z Thu Jan 1 00:00:00 1970 From: Germano Percossi Subject: Re: [PATCH 28/57] libmultipath: use a shared lock to co-operate with udev Date: Tue, 3 May 2016 16:31:19 +0100 Message-ID: <5728C447.9050307@citrix.com> References: <1461755458-29225-1-git-send-email-hare@suse.de> <1461755458-29225-29-git-send-email-hare@suse.de> <20160502162617.GS26117@octiron.msp.redhat.com> <57283DAD.9040009@suse.de> <20160503142732.GB26117@octiron.msp.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160503142732.GB26117@octiron.msp.redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: dm-devel@redhat.com List-Id: dm-devel.ids Hi, Sorry for jumping in the middle of patch review On 05/03/2016 03:27 PM, Benjamin Marzinski wrote: > On Tue, May 03, 2016 at 07:57:01AM +0200, Hannes Reinecke wrote: >> On 05/02/2016 06:26 PM, Benjamin Marzinski wrote: >>> On Wed, Apr 27, 2016 at 01:10:29PM +0200, Hannes Reinecke wrote: >> This is primarily for co-operation with udev. >> As we typically do _not_ use multipath for creating device-mapper tables >> the synchronisation problem between multipath and multipathd >> doesn't typically occur. >> At least not for us :-) > > Well, it doesn't occur for us either, unless someone runs multipath at > EXACTLY the wrong time, at which case, I'm pretty sure the same thing > can happen in any distro. The question is, do we protect against that > very unlikely occurance. The only time I see this actually having any > real chance to occur would be if some multipath user writes a script > that listens for new devices to be discovered, and then *helpfully* runs > multipath to update the system. I have seen this. Multiple times, in > fact. I'm not sure how much work we need to expend saving these people > from themselves, however. > I just want to make sure XenServer is not among those that need to be saved from themselves. We do mix multipathd and multipath commands but in a way that we think is safe: we add devices with "multipath -r" and remove with "multipath -f". This is because we slightly bend the wwids file usage to be used as a blacklisting mechanism (in our own way). I am wondering if removing cooperation between multipath and multipathd is going to cause us troubles in the future. Regards, Germano