On 4/6/20 12:35 AM, Valdis Klētnieks wrote:
What is the actual device backing this block device?
There's no real device behind the driver: it's just writing the data on the memory.
That's called a read-modify-write (RMW) cycle, and is used when a write request isn't exactly one physical block long, and it happens for file devices as well, it's just hidden by the file system layer.
I understand this, but I don't understand why it's using 4096 as unit rather than 512 that is the logical (and physical) block size I set for the queue using blk_queue_logical_block_size(). What's the relation between actual block size and the size of a segment (the bv_len field of the bio_vec struct) ? Is it related somehow to the page size? Does a segment need to be at least long as the page size? For example I've noticed that blk_queue_max_segment_size() will set the max segment size to PAGE_SIZE if the given size it's < PAGE_SIZE. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
