ver, when the device is busy, the pool may already be empty and the ioctl fails. Usually this can be recovered by calling the ioctl again, but in a situation in which we need to issue an unconditional reserve to make a device operational again, this would be not recoverable. To avoid a failure due to lack of memory, DASD device driver will preallocate enough memory for a single reserve/release request, which can be used if normal allocation fails. Signed-off-by: Stefan Weinhuber Signed-off-by: Martin Schwidefsky ôNScž'x