>>>>> "Andy" == Andy Grover <agrover@xxxxxxxxxx> writes: Hey Andy, Andy> ...because limits.max_hw_sectors internally seems to be just the Andy> controller limit, but what users of queue_max_hw_sectors Andy> (including sysfs) really want is the lesser of Andy> limits.max_hw_sectors and limits.max_dev_sectors. max_dev_sectors is a limit reported by the target device for READ/WRITE/VERIFY requests. Whereas max_hw_sectors describes the DMA constraints of the controller. It is a requirement for SG_IO, firmware updates, tape drives, etc. that the controller limits are reported correctly since they do I/Os that are much bigger than typical filesystem requests. When we tried to conflate the two things broke in interesting ways. I can't remember why the max_dev_sectors sysfs export patch didn't go in. But instead (or in addition) we could entertain having a max_rw_sectors_kb file that reflects the biggest READ/WRITE/VERIFY request the device can consume if that's the information you're after? -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
