From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 01/10] pktcdvd: remove the call to blk_queue_bounce Date: Mon, 19 Jun 2017 17:18:41 +0200 Message-ID: <20170619151841.GA12068@lst.de> References: <20170619072628.12894-1-hch@lst.de> <20170619072628.12894-2-hch@lst.de> <20170619150022.GA10165@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Ming Lei Cc: Jens Axboe , linux-block , "open list:DEVICE-MAPPER (LVM)" , Christoph Hellwig List-Id: dm-devel.ids On Mon, Jun 19, 2017 at 11:13:46PM +0800, Ming Lei wrote: > On Mon, Jun 19, 2017 at 11:00 PM, Christoph Hellwig wrote: > > On Mon, Jun 19, 2017 at 10:34:36PM +0800, Ming Lei wrote: > >> blk_queue_make_request() sets bounce for any highmem page for long time, > >> and in theory this patch might cause regression on 32bit arch, when > >> the controller can't handle higmem page really(especially in case of PAE), so > >> we may need to be careful about this change, especially on some old hardware. > > > > Which controller? > > I don't know. > > IMO, we can't just remove it because it is a bio based driver, the > bounce is not related with > a bio or req based driver, and it depends if the controller can handle > highmem page. pktcdvd is a stacking driver and forwards all data through either generic_make_request or blk_rq_map_kern + blk_execute_rq, both of which call blk_queue_bounce internally. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 19 Jun 2017 17:18:41 +0200 From: Christoph Hellwig To: Ming Lei Cc: Christoph Hellwig , Jens Axboe , linux-block , "open list:DEVICE-MAPPER (LVM)" Subject: Re: [PATCH 01/10] pktcdvd: remove the call to blk_queue_bounce Message-ID: <20170619151841.GA12068@lst.de> References: <20170619072628.12894-1-hch@lst.de> <20170619072628.12894-2-hch@lst.de> <20170619150022.GA10165@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-ID: On Mon, Jun 19, 2017 at 11:13:46PM +0800, Ming Lei wrote: > On Mon, Jun 19, 2017 at 11:00 PM, Christoph Hellwig wrote: > > On Mon, Jun 19, 2017 at 10:34:36PM +0800, Ming Lei wrote: > >> blk_queue_make_request() sets bounce for any highmem page for long time, > >> and in theory this patch might cause regression on 32bit arch, when > >> the controller can't handle higmem page really(especially in case of PAE), so > >> we may need to be careful about this change, especially on some old hardware. > > > > Which controller? > > I don't know. > > IMO, we can't just remove it because it is a bio based driver, the > bounce is not related with > a bio or req based driver, and it depends if the controller can handle > highmem page. pktcdvd is a stacking driver and forwards all data through either generic_make_request or blk_rq_map_kern + blk_execute_rq, both of which call blk_queue_bounce internally.