ublk: don't take ublk_queue in ublk_unregister_io_buf()

UBLK_IO_UNREGISTER_IO_BUF currently requires a valid q_id and tag to be
passed in the ublksrv_io_cmd. However, only the addr (registered buffer
index) is actually used to unregister the buffer. There is no check that
the q_id and tag are for the ublk request whose buffer is registered at
the given index. To prepare to allow userspace to omit the q_id and tag,
check the UBLK_F_SUPPORT_ZERO_COPY flag on the ublk_device instead of
the ublk_queue.

Signed-off-by: Caleb Sander Mateos <[e-mail]>
Reviewed-by: Ming Lei <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

drivers/block/ublk_drv.c

···
 }
 
 static int ublk_unregister_io_buf(struct io_uring_cmd *cmd,
-				  const struct ublk_queue *ubq,
+				  const struct ublk_device *ub,
 				  unsigned int index, unsigned int issue_flags)
 {
-	if (!ublk_support_zero_copy(ubq))
+	if (!(ub->dev_info.flags & UBLK_F_SUPPORT_ZERO_COPY))
 		return -EINVAL;
 
 	return io_buffer_unregister_bvec(cmd, index, issue_flags);
···
 	case UBLK_IO_REGISTER_IO_BUF:
 		return ublk_register_io_buf(cmd, ubq, io, ub_cmd->addr, issue_flags);
 	case UBLK_IO_UNREGISTER_IO_BUF:
-		return ublk_unregister_io_buf(cmd, ubq, ub_cmd->addr, issue_flags);
+		return ublk_unregister_io_buf(cmd, ub, ub_cmd->addr, issue_flags);
 	case UBLK_IO_COMMIT_AND_FETCH_REQ:
 		ret = ublk_commit_and_fetch(ubq, io, cmd, ub_cmd, issue_flags);
 		if (ret)