On Mon, Jun 19, 2017 at 11:18 PM, Christoph Hellwig <hch@xxxxxx> wrote: > On Mon, Jun 19, 2017 at 11:13:46PM +0800, Ming Lei wrote: >> On Mon, Jun 19, 2017 at 11:00 PM, Christoph Hellwig <hch@xxxxxx> 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. OK, thanks for explaining, then looks it isn't needed from the start. Thanks, Ming Lei
