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

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Date:	Wed, 26 Mar 2008 12:30:40 +0100
From:	Bodo Eggert <7eggert@....de>
To:	Greg KH <gregkh@...e.de>, "H. Peter Anvin" <hpa@...or.com>,
	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 ?

Greg KH <gregkh@...e.de> wrote:
> On Tue, Mar 25, 2008 at 04:05:32PM -0700, H. Peter Anvin wrote:

>>> 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?
>>
>> Any time you want to get the sysfs information for a filesystem which is
>> already mounted, that's what you're forced to do.
>>
>>> I thought we were talking about 2TB disks here, with a proposed new
>>> ioctl, not foolishness of boot scripts...
>>
>> I pointed out that having a way to map device numbers to sysfs directories
>> would have the same effect, *and* would be usable for other purposes.  I'd
>> rather see that than a new ioctl, and another, and another...
> 
> Again, a simple udev rule will give you that today if you really want
> it...

So e.g. lilo should depend on sysfs and *a*special*configuration* of udev,
while the admin MUST NOT use mknod'ed device files nor manually create
symlinks pointing to them, and not use relative path names?
That's plain stupid.

> And I think 'udevinfo' can be used to retrieve this information as well.

$ udevinfo /dev/hda
missing option
$ udevinfo /dev/hda --help
Usage: udevinfo OPTIONS
  --query=<type>    query database for the specified value:
    name            name of device node
    symlink         pointing to node
    path            sysfs device path
    env             the device related imported environment
    all             all values

  --path=<devpath>  sysfs device path used for query or chain
  --name=<name>     node or symlink name used for query

  --root            prepend to query result or print udev_root
  --attribute-walk  print all SYSFS_attributes along the device chain
  --export-db       export the content of the udev database
  --help            print this text
$ udevinfo --name=/dev/hda
missing option
$ udevinfo --name=/dev/hda --query=all
P: /block/hda
N: hda
S: disk/by-id/ata-Maxtor_2F040L0_F1748ZQE
S: disk/by-path/pci-0000:00:0f.0-ide-0:0
E: DEVTYPE=disk
E: ID_TYPE=disk
E: ID_MODEL=Maxtor_2F040L0
E: ID_SERIAL=F1748ZQE
E: ID_REVISION=VAM51JJ0
E: ID_BUS=ata
E: ID_PATH=pci-0000:00:0f.0-ide-0:0


As you can see, it gives no major:minor information. But it is in the DB:

$ cd /dev/.udev/db
$ grep -l hda * 2>/dev/null
\x2fblock\x2fhda
\x2fblock\x2fhda\x2fhda1
$ cat "\x2fblock\x2fhda"
N:hda
S:disk/by-id/ata-Maxtor_2F040L0_F1748ZQE
S:disk/by-path/pci-0000:00:0f.0-ide-0:0
M:3:0
E:DEVTYPE=disk
E:ID_TYPE=disk
E:ID_MODEL=Maxtor_2F040L0
E:ID_SERIAL=F1748ZQE
E:ID_REVISION=VAM51JJ0
E:ID_BUS=ata
E:ID_PATH=pci-0000:00:0f.0-ide-0:0

What a great tool - for making linux look bad.


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