Hi,
I'm a newbie in the mdadm world. I defined some udev rules to make disk
staticly named according to the bus/host/target. I.e. /dev/sda become
/dev/raid_disk0. So nothing very special with that, it's just a convenient way
to assign disk name to it's physical location.
#ls -la /dev/raid*
brw-rw---- 1 root disk 8, 0 2009-10-16 18:12 /dev/raid_disk0
brw-rw---- 1 root disk 8, 16 2009-10-16 18:12 /dev/raid_disk1
A RAID1 (/dev/md0) is assembled over this two disk.
When looking for detailed information, mdadm show annoying device name in
place of /dev/raid_disk*:
---8x---
#mdadm --detail /dev/md0
/dev/md0:
Version : 0.90
Creation Time : Tue Oct 13 12:53:54 2009
Raid Level : raid1
Array Size : 488386496 (465.76 GiB 500.11 GB)
Used Dev Size : 488386496 (465.76 GiB 500.11 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Wed Oct 21 15:16:09 2009
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
UUID : 3fea95a0:e1b8a341:3b119117:e416f62b
Events : 0.1526
Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/char/21:0
1 8 16 1 active sync /dev/char/21:1
---8x---
Looking in the source code of mdadm I found that the device name selection
rule is (too) simply: select the shortest name in case of multiple
possibility. So '/dev/char/21:0' being shorter than '/dev/raid_disk0', mdadm
display '/dev/char...'. It's annoying for me to see a CHAR (/dev/char/...)
device to represent a hard disk (wich is is a block device of course). The
purpose of the following patch is to handle the directory part to always
prefere the name that is closer to /dev. In case of equality, the shorter name
wins.
---8x---
#./mdadm --detail /dev/md0
/dev/md0:
Version : 0.90
Creation Time : Tue Oct 13 12:53:54 2009
Raid Level : raid1
Array Size : 488386496 (465.76 GiB 500.11 GB)
Used Dev Size : 488386496 (465.76 GiB 500.11 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Wed Oct 21 15:30:34 2009
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
UUID : 3fea95a0:e1b8a341:3b119117:e416f62b
Events : 0.1526
Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/raid_disk0
1 8 16 1 active sync /dev/raid_disk1
---8x---
Fell free to refactor the code. The last time I wrote C code I still had hair
on my head ;-)
---8x---
--- /var/tmp/mdadm_snapshot/util.c 2009-10-20 04:50:23.000000000 +0200
+++ /var/tmp/mdadm_dirlevel/util.c 2009-10-20 13:13:32.000000000 +0200
@@ -507,6 +507,38 @@
#endif /* HAVE_FTW */
#endif /* HAVE_NFTW */
+char *select_by_directory_level(char *current, char *registered)
+{
+ unsigned int current_level = 0;
+ unsigned int registered_level = 0;
+
+ unsigned int level(char *pathname)
+ {
+ unsigned int count = 0;
+ char *p = pathname;
+
+ while ( (p = strchr( p, '/' )) ) {
+ count++;
+ p++;
+ }
+
+ return( count );
+ }
+
+ current_level = level( current );
+ registered_level = level( registered );
+
+ if ( current_level < registered_level )
+ return current;
+
+ if ( current_level == registered_level )
+ if ( strlen( strrchr( current, '/')) <
+ strlen( strrchr( registered,'/')) )
+ return current;
+
+ return registered;
+}
+
/*
* Find a block device with the right major/minor number.
* If we find multiple names, choose the shortest.
@@ -544,14 +576,18 @@
if (p->major == major &&
p->minor == minor) {
if (strncmp(p->name, "/dev/md/",8) == 0) {
- if (preferred == NULL ||
- strlen(p->name) < strlen(preferred))
- preferred = p->name;
- } else {
- if (regular == NULL ||
- strlen(p->name) < strlen(regular))
- regular = p->name;
- }
+ if (preferred == NULL)
+ preferred = p->name;
+ else
+ preferred =
select_by_directory_level(
+ p->name,
preferred );
+ } else {
+ if (regular == NULL )
+ regular = p->name;
+ else
+ regular = select_by_directory_level(
+ p->name, regular );
+ }
}
if (!regular && !preferred && !did_check) {
devlist_ready = 0;
---8x---
Stéphane Bunel.
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