From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing Date: Thu, 18 Jul 2013 13:12:50 -0600 Message-ID: <51E83E32.9050306@cs.wisc.edu> References: <20130521235003.GE6985@mtj.dyndns.org> <20130522143923.GD19383@dhcp-26-207.brq.redhat.com> <20130522170305.GD9563@kernel.dk> <20130711102630.GA11133@dhcp-26-207.brq.redhat.com> <1373583637.7397.370.camel@haakon3.risingtidesystems.com> <20130712074559.GA8727@dhcp-26-207.brq.redhat.com> <1373692812.7397.625.camel@haakon3.risingtidesystems.com> <20130716183207.GA6402@dhcp-26-207.brq.redhat.com> <1374010683.7397.880.camel@haakon3.risingtidesystems.com> <20130717161909.GB21468@dhcp-26-207.brq.redhat.com> <1374173515.7397.948.camel@haakon3.risingtidesystems.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from sabe.cs.wisc.edu ([128.105.6.20]:36966 "EHLO sabe.cs.wisc.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754893Ab3GRTcS (ORCPT ); Thu, 18 Jul 2013 15:32:18 -0400 In-Reply-To: <1374173515.7397.948.camel@haakon3.risingtidesystems.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: "Nicholas A. Bellinger" Cc: Alexander Gordeev , Tejun Heo , linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, Jeff Garzik , Jens Axboe , linux-scsi On 07/18/2013 12:51 PM, Nicholas A. Bellinger wrote: > On Wed, 2013-07-17 at 18:19 +0200, Alexander Gordeev wrote: >> On Tue, Jul 16, 2013 at 02:38:03PM -0700, Nicholas A. Bellinger wrote: >>> [ 7.927818] scsi_execute(): Calling blk_mq_free_request >>> >>> [ 7.927826] scsi 0:0:0:0: Direct-Access ATA ST9500530NS CC03 PQ: 0 ANSI: 5 >>> >>> OK, so INQUIRY response payload is looking as expected here. >> >> Yep. It is not on the top of my head, but I remember something like INQUIRYs >> are emulated and thus do not have payload. >> >>> [ 7.927960] sd 0:0:0:0: [sda] Sector size 0 reported, assuming 512. >>> [ 7.927964] sd 0:0:0:0: [sda] 1 512-byte logical blocks: (512 B/512 B) >>> [ 7.927965] sd 0:0:0:0: [sda] 0-byte physical blocks >>> >>> Strange.. READ_CAPACITY appears to be returning a payload as zeros..? >> >> Yep. Because blk_execute_rq() does not put the proper callback and data do >> not get copied from sg's to bounce buffer. That is why I tried to use >> blk_mq_execute_rq() instead. Once I do that, data start getting read and >> booting stops elsewhere. > > Mmmmmm. > > The call to blk_queue_bounce() exists within blk_mq_make_request(), but > AFAICT this should still be getting invoked regardless of if the struct > request is dispatched into blk-mq via the modified blk_execute_rq() -> > blk_execute_rq_nowait() -> blk_mq_insert_request() codepath, or directly > via blk_mq_execute_rq().. > blk_mq_make_request is not called from the blk insert/execute paths. blk_mq_make_request takes a bio and tries to merge it with a request and adds it to the queue. It is only called when the make_request_fn is called like when generic_make_request is called. blk_mq_insert_request adds a already formed request to the queue. It is already formed so that is why that path does not bounce bios. The bios/pages should already be added within the drivers restrictions. So for the read_cap path, the call to blk_rq_map_kern in scsi_execute does the blk_queue_bounce call. Just saw this while trying out iscsi with the scsi-mq stuff :)