From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bartlomiej Zolnierkiewicz" Subject: Re: [PATCH 4/4] block: add large command support Date: Thu, 17 Apr 2008 13:58:37 +0200 Message-ID: <58cb370e0804170458l51453671vf5bf6c27d67f1920@mail.gmail.com> References: <20080416075743R.fujita.tomonori@lab.ntt.co.jp> <20080416083305.GY12774@kernel.dk> <4805C209.6040606@panasas.com> <20080417123218V.tomof@acm.org> <20080417070704.GO12774@kernel.dk> <58cb370e0804170455i58a8165fuc4b675c034217bd5@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mu-out-0910.google.com ([209.85.134.189]:9201 "EHLO mu-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751406AbYDQL6k (ORCPT ); Thu, 17 Apr 2008 07:58:40 -0400 Received: by mu-out-0910.google.com with SMTP id i10so44004mue.1 for ; Thu, 17 Apr 2008 04:58:39 -0700 (PDT) In-Reply-To: <58cb370e0804170455i58a8165fuc4b675c034217bd5@mail.gmail.com> Content-Disposition: inline Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jens Axboe Cc: FUJITA Tomonori , bharrosh@panasas.com, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, akpm@linux-foundation.org On Thu, Apr 17, 2008 at 1:55 PM, Bartlomiej Zolnierkiewicz wrote: > > On Thu, Apr 17, 2008 at 9:07 AM, Jens Axboe wrote: > > > > On Thu, Apr 17 2008, FUJITA Tomonori wrote: > > > On Wed, 16 Apr 2008 12:08:25 +0300 > > > Boaz Harrosh wrote: > > > > > > > On Wed, Apr 16 2008 at 11:33 +0300, 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. > > > > > > > > > > > > > Just a patch that I had for ages since the bad old request bidi times, > > > > perhaps is also good today. (rebased to for-2.6.26 branch) > > > > --- > > > > From: Boaz Harrosh > > > > Date: Wed, 16 Apr 2008 12:05:33 +0300 > > > > Subject: [PATCH] Initialize all members of struct request in rq_init > > > > > > > > Before, every member added/removed from struct request would entitle a change > > > > to rq_init, for initialization. Now all members are default to zero and only > > > > the none zero members are specifically initialized. > > > > > > > > Users that need requests on the stack or pre-allocated, must call rq_init() > > > > before use. > > > > > > > > Signed-off-by: Boaz Harrosh > > > > --- > > > > block/blk-core.c | 22 ++-------------------- > > > > 1 files changed, 2 insertions(+), 20 deletions(-) > > > > > > > > diff --git a/block/blk-core.c b/block/blk-core.c > > > > index 6f0968f..3f4c563 100644 > > > > --- a/block/blk-core.c > > > > +++ b/block/blk-core.c > > > > @@ -113,36 +113,18 @@ EXPORT_SYMBOL(blk_get_backing_dev_info); > > > > */ > > > > void rq_init(struct request_queue *q, struct request *rq) > > > > { > > > > + memset(rq, 0, sizeof(*rq)); > > > > > > Hmm, rq_init comment says: > > > > > > /* > > > * We can't just memset() the structure, since the allocation path > > > * already stored some information in the request. > > > */ > > > > > > I think that we can't initialize rq->cmd_flags here. > > > > That is correct, the patch wont work as-is. The principle of clearing > > every member except block internal is sound and should be applied, > > though. > > While we're at it we may fix it as well (preferably in another pre-patch): > > - move setting rq->cmd_flags from blk_alloc_request() to the callers > (this is only get_request() ATM) ditto for elv_set_request() call > - re-order setting rq->cmd_flags vs calling rq_init() in get_request(), > queue_lfush() and start_ordered()