Re: Device Major max and Disk Max in 2.4.x kernel

[Martin Dalecki <dalecki@evision-ventures.com>]

"Dupuis, Don" wrote:
> 
> I have already sent a patch to Alan and Linus on this issue.  Linus has
> never responed and Alan said he would look into it in the middle of April.
> Nothing is new at this point
> 
> -----Original Message-----
> From: PhiloVivero [mailto:pvspam-dntrepl@hacklab.net]
> Sent: Sunday, April 22, 2001 12:12 AM
> To: linux-kernel@vger.kernel.org
> Cc: sebastien.godard@wanadoo.fr; timb@claire.org; axboe@suse.de;
> phiviv@hacklab.net
> Subject: Device Major max and Disk Max in 2.4.x kernel
> 
> I have a problem. Trying to write an iostat for Linux (or use an existing
> one):
> 
> >From the kernel source:
> 
> [/usr/src/linux-2.4.2/include/linux] :) grep DK_MAX *.h
> kernel_stat.h:#define DK_MAX_MAJOR 16
> kernel_stat.h:#define DK_MAX_DISK 16
> 
> What to notice: MAJOR and DISK max are 16.
> 
> Again, from the kernel source:
> 
> [/usr/src/linux-2.4.2/fs/proc] :) grep -15 DK_MAX proc_misc.c
> <snip>
>     for (major = 0; major < DK_MAX_MAJOR; major++) {
>             for (disk = 0; disk < DK_MAX_DISK; disk++) {
>                     int active = kstat.dk_drive[major][disk] +
>                             kstat.dk_drive_rblk[major][disk] +
>                             kstat.dk_drive_wblk[major][disk];
>                     if (active)
>                             len += sprintf(page + len,
>                                     "(%u,%u):(%u,%u,%u,%u,%u) ",
>                                     major, disk,
>                                     kstat.dk_drive[major][disk],
>                                     kstat.dk_drive_rio[major][disk],
>                                     kstat.dk_drive_rblk[major][disk],
>                                     kstat.dk_drive_wio[major][disk],
>                                     kstat.dk_drive_wblk[major][disk]
>                     );
>             }
>     }
> 
> What to notice: We are looping up to the DK_MAX_MAJOR and DK_MAX_DISK. What
> this means is, any major >16 or disk >16 won't be listed in /proc/stat under
> the "disk_io" section.
> 
> Problem. On my system, which I figure is not too uncommon, I have several
> partitions on two hard drives and a CDROM. They are configured thusly:
> 
> # cat /proc/partitions
> major minor  #blocks  name
>    3     0   20094480 hda
>    3     1    6313513 hda1
>    3     2     401625 hda2
>    3     3   13374112 hda3
>    3    64    4497152 hdb
>   56     0   45034920 hdi
>   56     1   22490968 hdi1
>   56     2   22539195 hdi2
> 
> What to notice: I have a drive on /dev/hdi (never mind why, it actually
> works)
> that is block major 56. Not only that, my cdrom device on /dev/hdb is block
> major 3, but minor number 64. I am assuming for disks, minor == disk. Sorry
> if
> this is an incorrect assumption.
> 
> No stats for /dev/hdi nor /dev/hdb ever show up in /proc/stat. Only for
> /dev/hda. On my other 2.4.2 system, with multiple hard drives under 16/16,
> I get multiple devices under /proc/stat.
> 
> The patch seems relatively easy. Change linux/include/linux/kernel_stat.h to
> allow block major up to 56 (in my case... 64 in general???) and disks up to
> 64
> (in my case).
> 
> But we might need more than 64 disks on a block major (there are MANY snips
> in
> this so-called cut 'n' paste, because I figure you don't want to see them
> all):
> 
> # l /dev/hd* | sort -n
> brw-rw----    1 root     disk       3,  79 Feb 22 08:57 /dev/hdb15
> brw-rw----    1 root     disk       3,  80 Feb 22 08:57 /dev/hdb16
> brw-rw----    1 root     disk      22,  79 Feb 22 08:57 /dev/hdd15
> brw-rw----    1 root     disk      22,  80 Feb 22 08:57 /dev/hdd16
> brw-rw----    1 root     disk      33,  79 Feb 22 08:57 /dev/hdf15
> brw-rw----    1 root     disk      33,  80 Feb 22 08:57 /dev/hdf16
> brw-rw----    1 root     disk      34,  79 Feb 22 08:57 /dev/hdh15
> brw-rw----    1 root     disk      34,  80 Feb 22 08:57 /dev/hdh16
> brw-rw----    1 root     disk      56, 126 Mar 25 17:14 /dev/hdj62
> brw-rw----    1 root     disk      56, 127 Mar 25 17:14 /dev/hdj63
> 
> What to notice: We have disks up to 127. I never see any block major over 64
> on my system. The /dev/hdj device isn't used on my system. /dev/hdi and
> /dev/hdj belong to a Promise RAID controller on a new-ish
> ASUS AMD motherboard.
> 
> Let me know if I can be of further service. I must bashfully admit that I'm
> not enough of a guru to recompile my kernel anymore, or I'd tweak the
> kernel_stat.h file and recompile myself to test this.
> 
> This is just hazy recollection, but I think the 2.2.x kernels have the same
> problem.

Just never thing about those stats - they just broken by design.