Dne 14.9.2015 v 02:29 Adam Nielsen napsal(a):
Hi all,
I'm trying to work out how to force-remove a dm device after the
underlying disks failed. Because the kernel is still trying to write
blocks to the failed devices, I can't unmount the filesystem, so I
don't seem to be able to just drop the data, get some errors, then have
everything unmounted and clean, ready to try again.
$ dmsetup remove backup
device-mapper: remove ioctl on backup failed: Device or resource busy
Command failed
Using --force says it will replace the device with one that returns I/O
errors which sounds perfect, but that just locks up:
$ dmsetup remove --force backup
^C^C^\^\
Running it through strace shows it getting stuck in the kernel:
$ strace dmsetup remove --force backup
[...]
access("/run/udev/control", F_OK) = 0
open("/dev/urandom", O_RDONLY) = 4
read(4, "\2\325", 2) = 2
semget(0xd4dd502, 1, IPC_CREAT|IPC_EXCL|0600) = 458754
semctl(458754, 0, SETVAL, 0x1) = 0
semctl(458754, 0, GETVAL, 0x7f254875c47a) = 1
close(4) = 0
semop(458754, {{0, 1, 0}}, 1) = 0
semctl(458754, 0, GETVAL, 0x7f254875c417) = 2
ioctl(3, DM_DEV_SUSPEND
Is there any way to forcefully remove a dm device, or do you have to
reboot to remove failed devices?
I'm running kernel 4.1.4.
You need to show your 'broken' table first.
i.e. you can't replace some targets in some cases (I think suspended thin-pool
with broken metadata cannot be replaced with error target)
However for the 'standard' linear device - you could always replace opened
device with error target with '--force'.
What you can't expect is 'device deletion' - as long as device is opened,
it will be present (even if all read & writes will be errored).
As long as kernel structures are in use - device remains present.
Also note - dmsetup remove supports --deferred removal (see man page).
Zdenek
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