Re: as_arq scheduler alloc with 2.6.0-test8-mm1

From: Nick Piggin <piggin@cyberone.com.au>
To: Amit Patel <patelamitv@yahoo.com>
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org,
	James Bottomley <James.Bottomley@steeleye.com>,
	Alexander Viro <viro@math.psu.edu>
Subject: Re: as_arq scheduler alloc with 2.6.0-test8-mm1
Date: Wed, 29 Oct 2003 15:48:38 +1100	[thread overview]
Message-ID: <3F9F46A6.3090901@cyberone.com.au> (raw)
In-Reply-To: <20031029043423.41171.qmail@web13004.mail.yahoo.com>

Amit Patel wrote:

>--- Nick Piggin <piggin@cyberone.com.au> wrote:
>
>>No, you're on the right track. Actually, in the
>>block device
>>you will allocate the queue, and the queue will then
>>allocate
>>the elevator. First see if the queue is being
>>properly allocated
>>and freed. If it is not, then the problem is in the
>>SCSI layer.
>>
>>
>>
>
>Hi Nick,
>
>During scsi_scan.c:scsi_probe_and_add_lun it allocates
>scsi device and request_queue to send the
>scsi_request. If during this scan it finds no device
>attached to target it will deallocate request__queue.
>But since there was no disk found it never called
>add_disk and so it never go through blk_register_queue
>function to register elevator queue. So during clean
>up it just calles blk_cleanup_queue which does _not_
>clean up elevator_data. 
>
>This is just what I think is happening by looking at
>the code. I might be missing something. But in this
>case either blk_cleanup_queue should clean elevator
>also as part of cleanup instead of it getting cleaned
>up through blk_unregister_queue or scsi  layer needs
>to make some changes during scan. I do not know what
>implication it might have if cleanup is done as part
>of blk_cleanup_queue on other kind of block devices. I
>will try to put this cleanup as part of
>blk_cleanup_queue to see if it works. 
>

Yeah that sounds right. This is due to elv-select.patch. Its
quite a rats nest in there though :(

What should be happening is blk_alloc_queue should register
the queue kobject, and blk_init_queue should allocate the
the elevator kobject (which should be registered in the process).

add_disk should just be taking a reference on the queue, and
add a symlink in sysfs to the real queue (I think). I have a
patch to do this, but it is a bit ugly because I don't know
where in sysfs to put the queue object.

Anyway, if this isn't going to be done before 2.6.0, I guess
Andrew you should drop by elv-select patches for now. That
doesn't fix anything, but it hides some of the problems.