Hello all,
What went wrong in the following scenario? BTRFS thinks that a device is
mounted while it is not.
BTRFS tools ver: Btrfs v0.19-101-g3891d2d
Uname: 3.1.0-rc7-686-pae
## Comment: Initially we had only root (/) mounted as btrfs
mount |grep btrfs
/dev/sdc2 on / type btrfs (rw,autodefrag)
## Comment: Create a new btrfs fs on /dev/sdg /dev/sdh /dev/sdl
mkfs.btrfs -m raid1 -d raid1 /dev/sdg /dev/sdh /dev/sdl
btrfs filesystem show
Label: none uuid: f0425f63-e486-4c10-adab-47a23085c8db
Total devices 3 FS bytes used 28.00KB
devid 3 size 2.00GB used 200.00MB path /dev/sdl
devid 2 size 1.00GB used 200.00MB path /dev/sdh
devid 1 size 768.00MB used 404.00MB path /dev/sdg
Label: none uuid: cc8211ba-6f62-46d6-ba17-49250f06a941
Total devices 1 FS bytes used 512.98MB
devid 1 size 6.09GB used 1.75GB path /dev/sdc2
## Comment: unorthodox, but looks possible, add one of the devices from
the newly created fs to root (/)
btrfs device add /dev/sdh /
## Comment: Remove it back.
btrfs device delete /dev/sdh /
## Comment: We ended up with "*** Some devices missing" on both
devices
btrfs filesystem show
Label: none uuid: 5910f378-0784-4e7f-b918-de35067252e9
Total devices 3 FS bytes used 28.00KB
devid 3 size 2.00GB used 200.00MB path /dev/sdl
devid 1 size 768.00MB used 404.00MB path /dev/sdg
*** Some devices missing
Label: none uuid: cc8211ba-6f62-46d6-ba17-49250f06a941
Total devices 2 FS bytes used 512.59MB
devid 1 size 6.09GB used 1.50GB path /dev/sdc2
*** Some devices missing
## Comment: Use btrfs balance to fix root (/)
btrfs filesystem balance /
btrfs filesystem show
Label: none uuid: 5910f378-0784-4e7f-b918-de35067252e9
Total devices 3 FS bytes used 28.00KB
devid 3 size 2.00GB used 200.00MB path /dev/sdl
devid 1 size 768.00MB used 404.00MB path /dev/sdg
*** Some devices missing
Label: none uuid: cc8211ba-6f62-46d6-ba17-49250f06a941
Total devices 1 FS bytes used 513.40MB
devid 1 size 6.09GB used 1.75GB path /dev/sdc2
## Comment: try to mount the initially created fs on /mnt. It fails
mount -t btrfs /dev/sdg /mnt
mount: wrong fs type, bad option, bad superblock on /dev/sdg,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
## Comment: See if device scan can do the trick. Nope...
btrfs device scan /dev/sdh
Scanning for Btrfs filesystems in ''/dev/sdh''
ERROR: unable to scan the device ''/dev/sdh'' - Invalid argument
## Comment: OK, we give up. Try to recreate btrfs from scratch
mkfs.btrfs -m raid1 -d raid1 /dev/sdg /dev/sdh /dev/sdl
WARNING! - Btrfs Btrfs v0.19 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using
/dev/sdh is mounted
## Comment: Of course /dev/sdh is not mounted.
mount |grep /dev/sdh
root@lxc:~#
Thanks,
Nikos
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Hallo, Nikos, Du meintest am 21.10.11:> What went wrong in the following scenario? BTRFS thinks that a device > is mounted while it is not.[...]> btrfs device scan /dev/sdh > Scanning for Btrfs filesystems in ''/dev/sdh'' > ERROR: unable to scan the device ''/dev/sdh'' - Invalid argument> ## Comment: OK, we give up. Try to recreate btrfs from scratch > mkfs.btrfs -m raid1 -d raid1 /dev/sdg /dev/sdh /dev/sdl> WARNING! - Btrfs Btrfs v0.19 IS EXPERIMENTAL > WARNING! - see http://btrfs.wiki.kernel.org before using> /dev/sdh is mounted> ## Comment: Of course /dev/sdh is not mounted. > mount |grep /dev/sdh > root@lxc:~#Two days ago I''ve seen a perhaps similar problem with an ext3 disk: Connected via USB running fsck (with some options) mount /dev/$disk $mountpoint also told that the disk was mounted (it wasn''t really). Maybe some other operation (like - in this case - fsck) on/with the disk leads to this wrong message. Viele Gruesse! Helmut -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
2011-10-21, 00:39(+03), Nikos Voutsinas: [...]> ## Comment: Of course /dev/sdh is not mounted. > mount |grep /dev/sdh > root@lxc:~#[...] Note that mount(8) uses /etc/mtab to find out what is mounted. And if that file is not a symlink to /proc/mounts, the information is not necessarily correct. You can also have a look at /proc/mounts directly. -- Stephane -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> 2011-10-21, 00:39(+03), Nikos Voutsinas: > [...] >> ## Comment: Of course /dev/sdh is not mounted. >> mount |grep /dev/sdh >> root@lxc:~# > [...] > > Note that mount(8) uses /etc/mtab to find out what is mounted. > And if that file is not a symlink to /proc/mounts, the > information is not necessarily correct. > > You can also have a look at /proc/mounts directly. >OK, I found what went wrong, however I am not sure whose fault this is and If I am going to describe a case that is already known to this list. To cut a long story short, the consecutive root@btrfs:~# btrfs device add /dev/sdc / root@btrfs:~# btrfs device delete /dev/sdc / led to inconsistency between the contents of /proc/mounts and /dev/disk/by-uuid (ie the mapping of UUIDs to devices). Actually, "btrfs device add /dev/sdc /" changed the mapping of root''s UUID to point to /dev/sdc, and the system left it this way, even after the "btrfs device delete /dev/sdc /". Thus I ended up with the following situation. root@btrfs:~# cat /etc/mtab /proc/mounts |grep btrfs /dev/sdd2 / btrfs rw 0 0 /dev/disk/by-uuid/cc8211ba-6f62-46d6-ba17-49250f06a941 / btrfs rw 0 0 root@btrfs:~# root@btrfs:~# ls -l /dev/disk/by-uuid/cc8211ba-6f62-46d6-ba17-49250f06a941 lrwxrwxrwx 1 root root 9 Oct 22 16:13 /dev/disk/by-uuid/cc8211ba-6f62-46d6-ba17-49250f06a941 -> ../../sdc Although this may be a udev issue, I think that the userspace tools of btrfs should have handled this in a better way. Nikos -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html