linux-kernel - Re: What to do about the 2TB limit on HDIO

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Date:	Tue, 25 Mar 2008 16:00:09 -0700
From:	Greg KH <gregkh@...e.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Randy Dunlap <randy.dunlap@...cle.com>, Mark Lord <lkml@....ca>,
	Jens Axboe <axboe@...nel.dk>, Jeff Garzik <jgarzik@...ox.com>,
	Tejun Heo <htejun@...il.com>,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	IDE/ATA development list <linux-ide@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: What to do about the 2TB limit on HDIO_GETGEO ?

On Tue, Mar 25, 2008 at 02:26:45PM -0700, H. Peter Anvin wrote:
> Greg KH wrote:
>> On Tue, Mar 25, 2008 at 01:36:51PM -0700, H. Peter Anvin wrote:
>>> Randy Dunlap wrote:
>>>>> Come on people, adding symlinks for device major:minor numbers in sysfs
>>>>> to save a few 10s of lines of userspace code?  Can things get sillier?
>>>>>
>>>>> You can add a single udev rule to probably build these in a tree in 
>>>>> /dev
>>>>> if you really need such a thing...
>>>>>
>>>>> And what's wrong with your new ioctl recomendation?
>>>> Ah, there's some sanity.  :)
>>> It's not so much an issue of a few tens of lines of user space code, but 
>>> rather the fact that something that should be O(1) is currently O(n).
>> "should"?  why?  Is this some new requirement that everyone needs?  I've
>> _never_ seen anyone ask for the ability to find sysfs devices by
>> major:minor number in O(1) time.  Is this somehow a place where such
>> optimization is warranted?
>
> Well, when dealing with shell scripts a O(n) very easily becomes O(n^2).  
> For the stuff that I, personally, do, it's not a big deal, but people with 
> large number of disks have serious gripes with our boot times.

How does this have anything to do with boot times?  Do you really have a
foolish shell script that iteratorates over every single disk in the
sysfs tree for every disk?  What does it do that for?

I thought we were talking about 2TB disks here, with a proposed new
ioctl, not foolishness of boot scripts...
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