linux-kernel - Re: [dm-devel] REQUEST for new 'topology' metrics to be moved out of the 'queue' sysfs directory.

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Message-ID: <4A48B75C.5080209@panasas.com>
Date:	Mon, 29 Jun 2009 15:45:16 +0300
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	NeilBrown <neilb@...e.de>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Mike Snitzer <snitzer@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alasdair G Kergon <agk@...hat.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-raid@...r.kernel.org, linux-ide@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	device-mapper development <dm-devel@...hat.com>
Subject: Re: [dm-devel] REQUEST for new 'topology' metrics to be moved out
 of the 'queue' sysfs directory.

On 06/29/2009 02:41 PM, Jens Axboe wrote:
> On Mon, Jun 29 2009, NeilBrown wrote:
>> On Mon, June 29, 2009 8:18 pm, Jens Axboe wrote:
>>> On Sat, Jun 27 2009, Neil Brown wrote:
>>>>> There's no such thing as first or second class block devices. The fact
>>>>> that drivers using ->make_request_fn directly do not utilize the full
>>>>> scope of the queue isn't a very interesting fact, imho.
>>>>  Your phrase "drivers using ->make_request_fn directly" seems to
>>>>  suggest you are looking at things very differently to me.
>>>>
>>>>  From my perspective, all drivers use ->make_request_fn equally.
>>>>  Some set it to "__make_request", some to "md_make_request", others to
>>>>  "dm_request" or "loop_make_request" etc.
>>> Neil, will you please stop these silly games. Stop trying to invent
>>> differences based on interpretations of what you read into my replies.
>>
>> We do seem to be having trouble communicating don't we :-(
>> Be assured that it is not my intention to play games, silly or otherwise.
>>
>> Maybe I should just try sending you patches.  Maybe that will
>> make my meaning clearer.
>>
>> For the moment, I'm much more interested in the other question,
>> that of whether I can avoid having a 'queue' directory introduced into
>> md/dm/etc device directories in sysfs.
> 
> We already talked about this, several times. My answer is that it seems
> pointless to begin with internally, and externally it just makes the API
> worse since tools then have to know which device type they are talking
> to.
> 

I do however see a problem with sysfs-files that mostly work for most devices
but for some "device type" they do nothing silently. At least make these
directory/files read-only for the un-used cases (eg. dm/md). And return proper
values to indicate their un-usefulness like "-1" or "NA"

> So I still see absolutely zero point in making such a change, quite the
> opposite.
> 

Just my $0.017
Boaz
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