Re: [PATCH 0/6] Support resize and device delete cancel ops

[Anand Jain <anand.jain@oracle.com>]

On 21/05/2021 20:06, David Sterba wrote:
> We don't have a nice interface to cancel the resize or device deletion
> from a command. Since recently, both commands can be interrupted by a
> signal, which also means Ctrl-C from terminal, but given the long
> history of absence of the commands I think this is not yet well known.
> 
> Examples:
> 
>    $ btrfs fi resize -10G /mnt
>    ...
>    $ btrfs fi resize cancel /mnt
> 
>    $ btrfs device delete /dev/sdx /mnt
>    ...
>    $ btrfs device delete cancel /mnt


David,

These cancel commands don't fail with un-supported ioctl error codes on 
the older kernels as we didn't define a new ioctl for this purpose.

Generally, the latest btrfs-progs are compatible with the older kernels, 
especially useful for the fsck fixes.

Moving forward does the newer btrfs-progs version will continue to be 
compatible with the older kernels?

Thanks Anand

> 
> The cancel request returns once the resize/delete command finishes
> processing of the currently relocated chunk. The btrfs-progs needs to be
> updated as well to skip checks of the sysfs exclusive_operation file
> added in 5.10 (raw ioctl would work).
> 
> David Sterba (6):
>    btrfs: protect exclusive_operation by super_lock
>    btrfs: add cancelable chunk relocation support
>    btrfs: introduce try-lock semantics for exclusive op start
>    btrfs: add wrapper for conditional start of exclusive operation
>    btrfs: add cancelation to resize
>    btrfs: add device delete cancel
> 
>   fs/btrfs/ctree.h      |  16 +++-
>   fs/btrfs/disk-io.c    |   1 +
>   fs/btrfs/ioctl.c      | 174 ++++++++++++++++++++++++++++++++----------
>   fs/btrfs/relocation.c |  60 ++++++++++++++-
>   4 files changed, 207 insertions(+), 44 deletions(-)
>