From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jun'ichi Nomura" Subject: Re: [PATCH v2] dm mpath: maintain reference count for underlying devices Date: Mon, 19 Sep 2011 15:49:12 +0900 Message-ID: <4E76E5E8.9040701@ce.jp.nec.com> References: <1316181571-4691-1-git-send-email-snitzer@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1316181571-4691-1-git-send-email-snitzer@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: device-mapper development Cc: "Alasdair G. Kergon" , Mike Snitzer List-Id: dm-devel.ids Hi Mike, On 09/16/11 22:59, Mike Snitzer wrote: > When processing a request, DM-mpath's map_io() set the cloned request's > request_queue to the appropriate underlying device's request_queue > without getting a reference on that request_queue. > > DM-mpath now maintains a reference count on the underlying devices' > request_queue. This change wasn't motivated by a specific report but > code, like blk_insert_cloned_request(), will access the request_queue > with the understanding that the request_queue is valid. Umm, I think it doesn't make sense. DM opens underlying devices and it should be sufficient to keep request_queue from being freed. If it was not enough, any other openers would have to get the reference count, too, and that should be done in more generic place. Thanks, -- Jun'ichi Nomura, NEC Corporation