Re: grub RAID heuristics (how can we avoid "superfluous RAID member (2 found)")

[Daniel Kahn Gillmor]

On Thu, 23 Feb 2012 06:43:23 +0100, Vladimir 'φ-coder/phcoder' Serbinenko 
<address@hidden> wrote:
> Try attached patch

hrm, i get a segmentation fault from "grub-probe /" even without this
patch when building from bzr trunk (r3964, i think).

The test machine i've set up looks like this uses a common layering
scheme:
 disk → partition → mdadm (0.90 superblock) → lvm → filesystem

Here are the details and a backtrace of me trying:

0 address@hidden:~# parted /dev/sda unit s print
Model: ATA WDC WD200BB-75DE (scsi)
Disk /dev/sda: 39062500s
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start      End        Size       Type     File system  Flags
 1      8192s      12542018s  12533827s  primary
 2      12550144s  39062499s  26512356s  primary

0 address@hidden:~# parted /dev/sdb unit s print
Model: ATA QUANTUM FIREBALL (scsi)
Disk /dev/sdb: 26520480s
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start  End        Size       Type     File system  Flags
 1      4096s  26520479s  26516384s  primary

0 address@hidden:~# cat /proc/mdstat 
Personalities : [raid1] 
md0 : active raid1 sdb1[0] sda2[1]
      13256064 blocks [2/2] [UU]
      
unused devices: <none>
0 address@hidden:~# pvs
  PV         VG        Fmt  Attr PSize  PFree
  /dev/md0   vg_trash0 lvm2 a--  12.64g 9.64g
0 address@hidden:~# vgs
  VG        #PV #LV #SN Attr   VSize  VFree
  vg_trash0   1   1   0 wz--n- 12.64g 9.64g
0 address@hidden:~# lvs
  LV   VG        Attr   LSize Origin Snap%  Move Log Copy%  Convert
  root vg_trash0 -wi-ao 3.00g                                      
0 address@hidden:~# grep ' / ' /proc/mounts 
rootfs / rootfs rw 0 0
/dev/mapper/vg_trash0-root / ext3 
rw,relatime,errors=remount-ro,user_xattr,acl,barrier=1,data=ordered 0 0
0 address@hidden:~# cd - 
/home/dkg/src/grub/grub
0 address@hidden:/home/dkg/src/grub/grub# gdb ./grub-probe
GNU gdb (GDB) 7.4-debian
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/dkg/src/grub/grub/grub-probe...(no debugging symbols 
found)...done.
(gdb) run -v /
Starting program: /home/dkg/src/grub/grub/grub-probe -v /
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to 
/dev/mapper.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to /dev.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to md.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to dri.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to snd.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-path.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to cpu.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to 
vg_trash0.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to /dev.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to md.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to dri.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to snd.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-path.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to cpu.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to 
vg_trash0.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to disk.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-uuid.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-path.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-id.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to block.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to /dev.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to md.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to dri.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to snd.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-path.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to cpu.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to 
vg_trash0.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to disk.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-uuid.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-path.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to by-id.
/home/dkg/src/grub/grub/grub-probe: info: changing current directory to block.
/home/dkg/src/grub/grub/grub-probe: info: Looking for /dev/sdb1.
/home/dkg/src/grub/grub/grub-probe: info: /dev/sdb1 starts from 4096.
/home/dkg/src/grub/grub/grub-probe: info: opening the device hd1.
/home/dkg/src/grub/grub/grub-probe: info: the size of hd1 is 26520480.
/home/dkg/src/grub/grub/grub-probe: info: the size of hd1 is 26520480.
/home/dkg/src/grub/grub/grub-probe: info: Scanning for DISKFILTER devices on 
disk hd1.
/home/dkg/src/grub/grub/grub-probe: info: no LVM signature found.
/home/dkg/src/grub/grub/grub-probe: info: Found array md/md0.
/home/dkg/src/grub/grub/grub-probe: info: Inserting hd1 into md/md0 (mdraid09)
.
/home/dkg/src/grub/grub/grub-probe: info: the size of hd1 is 26520480.
/home/dkg/src/grub/grub/grub-probe: info: Scanning for DISKFILTER devices on 
disk md/md0.
/home/dkg/src/grub/grub/grub-probe: info: no LVM signature found.
/home/dkg/src/grub/grub/grub-probe: info: scanning md/md0 for LDM.
/home/dkg/src/grub/grub/grub-probe: info: no LDM signature found.
/home/dkg/src/grub/grub/grub-probe: info: Scanning for DISKFILTER devices on 
disk md/md0.
/home/dkg/src/grub/grub/grub-probe: info: Found array vg_trash0.
/home/dkg/src/grub/grub/grub-probe: info: Inserting md/md0 into vg_trash0 (lvm)
.
/home/dkg/src/grub/grub/grub-probe: info: Scanning for DISKFILTER devices on 
disk lvm/vg_trash0-root.
/home/dkg/src/grub/grub/grub-probe: info: no LVM signature found.
/home/dkg/src/grub/grub/grub-probe: info: scanning lvm/vg_trash0-root for LDM.
/home/dkg/src/grub/grub/grub-probe: info: no LDM signature found.
/home/dkg/src/grub/grub/grub-probe: info: Scanning for DISKFILTER devices on 
disk hd1.
/home/dkg/src/grub/grub/grub-probe: info: Inserting hd1 into vg_trash0 (lvm)
.

Program received signal SIGSEGV, Segmentation fault.
0x080e7850 in grub_util_get_ldm ()
(gdb) bt
#0  0x080e7850 in grub_util_get_ldm ()
#1  0x080d834e in grub_util_biosdisk_get_grub_dev ()
#2  0x080d7195 in grub_util_pull_device ()
#3  0x080d716a in grub_util_pull_device ()
#4  0x080d7081 in grub_util_pull_device ()
#5  0x0804ab2c in probe ()
#6  0x0804bcdc in main ()
(gdb) 


Applying the patch doesn't help me avoid the segfault.

So i haven't really tested the patch.

   --dkg

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