Support for a new command that can be used eg. as a command
$ btrfs device scan --forget [dev]'
(the final name may change though)
to undo the effects of 'btrfs device scan [dev]'. For this purpose
this patch proposes to use ioctl #5 as it was empty and is next to the
SCAN ioctl.
The new ioctl BTRFS_IOC_FORGET_DEV works only on the control device
(/dev/btrfs-control) to unregister one or all devices, devices that are
not mounted.
The argument is struct btrfs_ioctl_vol_args, ::name specifies the device
path. To unregister all device, the path is an empty string.
Again, the devices are removed only if they aren't part of a mounte
filesystem.
This new ioctl provides:
- release of unwanted btrfs_fs_devices and btrfs_devices structures
from memory if the device is not going to be mounted
- ability to mount filesystem in degraded mode, when one devices is
corrupted like in split brain raid1
- running test cases which would require reloading the kernel module
but this is not possible eg. due to mounted filesystem or built-in
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
228a73abde