rdsv3_message_alloc
rm = rdsv3_message_alloc(ceil(total_len, PAGE_SIZE), KM_NOSLEEP);
rm = rdsv3_message_alloc(ceil(total_len, PAGE_SIZE), KM_NOSLEEP);
rm = rdsv3_message_alloc(0, KM_NOSLEEP);
struct rdsv3_message *rdsv3_message_alloc(unsigned int nents, int gfp);