blk_queue_chunk_sectors - set size of the chunk for this queue
void blk_queue_chunk_sectors(struct request_queue * q, unsigned int chunk_sectors);
If a driver doesn't want IOs to cross a given chunk size, it can set this limit and prevent merging across chunks. Note that the chunk size must currently be a power-of-2 in sectors. Also note that the block layer must accept a page worth of data at any offset. So if the crossing of chunks is a hard limitation in the driver, it must still be prepared to split single page bios.
|January 2017||Kernel Hackers Manual 4.8.|