Re: mdadm --detail showing annoying device

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

Stephane Bunel a écrit :
> Mario 'BitKoenig' Holbe a écrit :
>> Neil Brown <neilb@suse.de> wrote:
>>> On Wednesday October 21, stephane.bunel@forumdesimages.fr wrote:
>>>>         0       8        0        0      active sync   /dev/char/21:0
>>>>         1       8       16        1      active sync   /dev/char/21:1
>>> What is a block device doing in /dev/char ???  There should only be
>>> character devices in there.
>>
>> major 21 are usually SCSI generic devices (/dev/sg) and they are char...
>> crw-rw----  1 root root  21, 0 Oct 10 21:48 /dev/sg0
>> crw-rw----  1 root root  21, 1 Oct 10 21:48 /dev/sg1
>>
>> The question is, why do they appear at mdadm --detail
> 
>   mdadm performs a physical walk to not follow symbolic links (cf nftw( 
> FTW_PHYS ) in map_dev() ). But using stat() mdadm finaly follow the 
> symbolic link and so returns the same type/major/minor as the targeted 
> link.
> 
>   lstat() is identical to stat(), except that if path is a symbolic 
> link, then the link itself is stat-ed, not the file that it refers to.
> 
> 
> #ls -la /dev/char/21:0
> lrwxrwxrwx 1 root root 13 2009-10-16 18:12 /dev/char/21:0 -> ../raid_disk0
> 
> Tested from Python:
>  >>> import os, stat
> 
> Using stat:
>  >>> mode = os.stat( '/dev/char/21:0' )[ stat.ST_MODE ]
>  >>> stat.S_ISBLK( mode )
> True
> 
> using lstat():
>  >>> mode = os.lstat( '/dev/char/21:0' )[ stat.ST_MODE ]
>  >>> stat.S_ISBLK( mode )
> False


Just for fun ;-)

--- util.c.orig	2009-10-22 17:54:11.000000000 +0200
+++ util.c	2009-10-22 17:55:09.000000000 +0200
@@ -468,7 +468,7 @@
  	struct stat st;

  	if (S_ISLNK(stb->st_mode)) {
-		if (stat(name, &st) != 0)
+		if (lstat(name, &st) != 0)
  			return 0;
  		stb = &st;
  	}



Stéphane Bunel.

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