Re: [RFC 0/5] block large commands support continue

[Boaz Harrosh <bharrosh@panasas.com>]

On Fri, Apr 25 2008 at 13:03 +0300, FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> On Fri, 25 Apr 2008 11:31:41 +0200
> Jens Axboe <jens.axboe@oracle.com> wrote:
> 
>> On Fri, Apr 25 2008, FUJITA Tomonori wrote:
>>> On Fri, 25 Apr 2008 11:22:04 +0200
>>> Jens Axboe <jens.axboe@oracle.com> wrote:
>>>
>>>> On Fri, Apr 25 2008, FUJITA Tomonori wrote:
>>>>> On Thu, 24 Apr 2008 12:49:30 +0200
>>>>> Jens Axboe <jens.axboe@oracle.com> wrote:
>>>>>
>>>>>> On Thu, Apr 24 2008, FUJITA Tomonori wrote:
>>>>>>> On Thu, 24 Apr 2008 13:31:21 +0900
>>>>>>> FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
>>>>>>>
>>>>>>>> On Wed, 23 Apr 2008 17:50:42 +0300
>>>>>>>> Boaz Harrosh <bharrosh@panasas.com> wrote:
>>>>>>>>
>>>>>>>>> The support for large commands was dropped from the for-2.6.26 branch
>>>>>>>>> and will probably not get accepted into next kernel.
>>>>>>>>>
>>>>>>>>> I have tried to take all comments from Jens and Bart. and incorporate
>>>>>>>>> it into a new patchset. This is basically Tomo's patchset but with
>>>>>>>>> proposed changes.
>>>>>>>> Have you seen the patchset to remove request on the stack?
>>>>>>>>
>>>>>>>> http://marc.info/?l=linux-ide&m=120882410712466&w=2
>>>>>>>>
>>>>>>>>
>>>>>>>>> They are based on current linux-block/master. They will probably conflict with
>>>>>>>>> latest patch sent by Tomo for the blk_get_request(). Once those patches
>>>>>>>>> get accepted at some git tree, (Where will that be?), I will rebase these
>>>>>>>>> on top of them. Please CC me of any progress.
>>>>>>>>>
>>>>>>>>> [PATCH 1/5] block: no need to initialize rq->cmd
>>>>>>>>>   This is 2 of Tomo's patches squashed together as they are
>>>>>>>>>   small and do the same. Tomo is this OK?
>>>>>>>>>
>>>>>>>>> [PATCH 2/5] block: replace sizeof(rq->cmd) with BLK_MAX_CDB
>>>>>>>>>   Tomos patch rebased to here
>>>>>>>>>
>>>>>>>>> [PATCH 3/5] block: Export rq_init, rename to blk_init_rq
>>>>>>>>> [PATCH 4/5] block: Use new blk_init_rq
>>>>>>>>>   These patches are basically what Jens and Bart has suggested, that with
>>>>>>>>>   a small code change to blk-core.c we can memset at rq_init() and only set
>>>>>>>>>   none zero members. We can also export that initializer and use it all over
>>>>>>>>>   the ide tree where ever requests don't come from a request queue. (OK also
>>>>>>>>>   at scsi_error.c)
>>>>>>>> +void blk_init_rq(struct request_queue *q, struct request *rq, int cmd_flags)
>>>>>>>>
>>>>>>>> Hmm, would it be better to modify the block layer to let rq_init just
>>>>>>>> memset() the request structure?
>>>>>>> I think, if we move rq_init to blk_alloc_request from get_request,
>>>>>>> rq_init can just memset() the structure.
>>>>>>>
>>>>>>> Then we can export rq_init and rq_init works for everyone.
>>>>>> Wont work, see the io scheduler set_request() functions.
>>>>> Sorry, can you be more specific?
>>>>>
>>>>> Only cfq uses set_request for now. cfq_set_request uses rq->cmd_flags
>>>>> and stores information at rq->elevator_private and
>>>>> rq->elevator_private2.
>>>>>
>>>>> The patch does memset() the request structure and sets up
>>>>> rq->cmd_flags, and then elv_set_request. Doesn't it work?
>>>> Sorry, with the moved rq_init() it should work, didn't look closely
>>>> enough.
>>> No problem.
>>>
>>> So are you ok with the patch? If so, I'll re-send it with a proper
>>> description and the signed-off.
>> Please do - I actually already merged it, but do resend with a full
>> description and signed-off etc.
> 
> I just stole your description and added my signed-off.
> 
> Will you merge the large command support for 2.6.26? Or only this
> clean-up patch?
> 
> =
> From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> Subject: [PATCH] block: make rq_init() do a full memset()
> 
> This requires moving rq_init() from get_request() to blk_alloc_request().
> The upside is that we can now require an rq_init() from any path that
> wishes to hand the request to the block layer.
> 
> rq_init() will be exported for the code that uses struct request
> without blk_get_request.
> 
> This is a preparation for large command support, which needs to
> initialize struct request in a proper way (that is, just doing a
> memset() will not work).
> 
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> ---
<snip>

Sorry for the late response. Those hebrew holidays on they way of Linux
coding ;-).

I don't mind as long as these things get accepted. But how is that any
different then the patch I sent?
  [PATCH 3/5] block: Export rq_init, rename to blk_init_rq
It does exactly 100% the same move of rq_init to blk_alloc_request and the memset and
all, Have you looked at the patches at all? I feel like a mute person ;-(

If you are going to export the rq_init function then I think the name is very
wrong. And you have not exported it?

Boaz