Yes you are right, there are some UNIXes that ship today without a buffer (block) cache and/or don't default to using the block cache when open(2)ing a block de

Yes you are right, there are some UNIXes that ship today without a buffer (block) cache and/or don't default to using the block cache when open(2)ing a block device. For those wondering Linux uses a unified buffer / page cache so there isn't a coherency issue. The buffer cache entries typically point to the corresponding entry in the page cache if it exists. The biggest reason the two are separate but correlated is that the block size isn't always the same as the page size.