From mboxrd@z Thu Jan 1 00:00:00 1970 From: FUJITA Tomonori Subject: Re: [PATCH 4/4] block: add large command support Date: Thu, 17 Apr 2008 13:02:00 +0900 Message-ID: <20080417125900E.tomof@acm.org> References: <200804160050.54842.bzolnier@gmail.com> <20080416075743R.fujita.tomonori@lab.ntt.co.jp> <20080416083305.GY12774@kernel.dk> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from mo10.iij4u.or.jp ([210.138.174.78]:52440 "EHLO mo10.iij4u.or.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750746AbYDQECs (ORCPT ); Thu, 17 Apr 2008 00:02:48 -0400 In-Reply-To: <20080416083305.GY12774@kernel.dk> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: jens.axboe@oracle.com Cc: fujita.tomonori@lab.ntt.co.jp, bzolnier@gmail.com, linux-scsi@vger.kernel.org, bharrosh@panasas.com, linux-ide@vger.kernel.org, akpm@linux-foundation.org On Wed, 16 Apr 2008 10:33:06 +0200 Jens Axboe wrote: > On Wed, Apr 16 2008, FUJITA Tomonori wrote: > > On Wed, 16 Apr 2008 00:50:54 +0200 > > Bartlomiej Zolnierkiewicz wrote: > > > > > > > > Hi, > > > > > > On Monday 14 April 2008, Jens Axboe wrote: > > > > On Mon, Apr 14 2008, FUJITA Tomonori wrote: > > > > > This patch changes rq->cmd from the static array to a pointer to > > > > > support large commands. > > > > > > > > > > We rarely handle large commands. So for optimization, a struct request > > > > > still has a static array for a command. rq_init sets rq->cmd pointer > > > > > to the static array. > > > > > > > > > > Signed-off-by: FUJITA Tomonori > > > > > Cc: Jens Axboe > > > > > --- > > > > > block/blk-core.c | 1 + > > > > > drivers/ide/ide-io.c | 1 + > > > > > include/linux/blkdev.h | 12 ++++++++++-- > > > > > 3 files changed, 12 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/block/blk-core.c b/block/blk-core.c > > > > > index 6669238..6f0968f 100644 > > > > > --- a/block/blk-core.c > > > > > +++ b/block/blk-core.c > > > > > @@ -132,6 +132,7 @@ void rq_init(struct request_queue *q, struct request *rq) > > > > > rq->errors = 0; > > > > > rq->ref_count = 1; > > > > > rq->cmd_len = 0; > > > > > + rq->cmd = rq->__cmd; > > > > > memset(rq->cmd, 0, BLK_MAX_CDB); > > > > > rq->data_len = 0; > > > > > rq->extra_len = 0; > > > > > diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c > > > > > index 7153796..bac5ea1 100644 > > > > > --- a/drivers/ide/ide-io.c > > > > > +++ b/drivers/ide/ide-io.c > > > > > @@ -1595,6 +1595,7 @@ void ide_init_drive_cmd (struct request *rq) > > > > > { > > > > > memset(rq, 0, sizeof(*rq)); > > > > > rq->ref_count = 1; > > > > > + rq->cmd = rq->__cmd; > > > > > } > > > > > > Tomo, some more changes are needed: > > > > > > Please think about all _static_/dynamic allocations of 'struct request' > > > used together with REQ_TYPE_SPECIAL etc., i.e. > > > > I think that using struct request allocated statically is wrong from > > the perspective of the block layer design, that is, you always need to > > use blk_get_request. I think that except ide, everyone does. > > > > I try to convert ide to use blk_get_request properly if you want. > > That would be best, but the on-stack allocation has the benefit that > it'll always work. So until we can completely get rid of that, lets just > make it a hard rule that ANY rq allocation MUST call rq_init(). It's a > lot saner than doing a memset() anyway. I'm fine with that. There is one minor issue. rq_init doesn't initialize rq->cmd_flags so the callers need to do it for themselves (If they don't, probably they hit BUG_ON in blk_queue_end_tag).