io_uring/ublk: report error when unregister operation fails
Indicate to userspace applications if a UBLK_IO_UNREGISTER_IO_BUF
command specifies an invalid buffer index by returning an error code.
Return -EINVAL if no buffer is registered with the given index, and
-EBUSY if the registered buffer is not a kernel bvec.
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Link: https://lore.kernel.org/r/20250228231432.642417-1-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>