Re: mdadm --detail showing annoying device

[Stephane Bunel <stephane.bunel@forumdesimages.fr>]

Beolach a écrit :
> On Tue, Nov 3, 2009 at 02:37, Stephane Bunel
> <stephane.bunel@forumdesimages.fr> wrote:
>> Neil Brown a écrit :
>> (...)
>>
>>> On your system, /dev/char/21:0 is a block device (or a link to a block
>>> device) so there is clearly some sort of configuration error.
>> All files in /dev/char are symlinks (see below). Rules are comming from
>> Gentoo.
>>
>>> If you still cannot find it, maybe you could show us the change you
>>> made to udev.rules, and an 'ls -l' of '/dev/char'.  That might help
>>> shed some light on your situation.
>> Considering mdadm is only involved by "real" block device file, why not just
>> skipping symlink ?
>>
>>  o Udev rules used to rename /dev/sd[ab]:
>>
>> #cat 65-persistent-block.rules
>> ENV{PHYSDEVPATH}=="/devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0",
>> NAME="raid_disk0"
>>
>> ENV{PHYSDEVPATH}=="/devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0",
>> NAME="raid_disk1"
>>
> 
> Try prepending SUBSYSTEM=="block" to those, so they they'll only match
> the (block) sd* devices, and not the (char) sg? devices:
> SUBSYSTEM=="block",
> ENV{PHYSDEVPATH}=="/devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0",
> NAME="raid_disk0"
> SUBSYSTEM=="block",
> ENV{PHYSDEVPATH}=="/devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0",
> NAME="raid_disk1"

Well done!! This correct the sg* link issue.

#mdadm --detail /dev/md0
(...)
     Number   Major   Minor   RaidDevice State
        0       8        0        0      active sync   /dev/block/8:0
        1       8       16        1      active sync   /dev/block/8:16
(...)

But we loop back to the original problem. mdadm show '/dev/block/8:0' instead 
of '/dev/raid_disk0' (as i wish). This because the symlink '/dev/block/8:0' is 
shorter than the real block file name '/dev/raid_disk0'.

Actual heuristic prevents renaming of real block device name as desired under 
penalty of seeing symlinks from /dev/block/*.

maybe mdadm could change this behavior by:

  o always prefers real bloc file over symlinks.
  o simply skips symlinks.
  o changing the heuristic like proposed by my patch (prefer the name that is 
closer to /dev).


Stéphane Bunel.


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