Evan, > Ah, I see. But I think it's useful to reflect max_discard_sectors, > max_write_zeroes_sectors, discard_granularity, and discard_alignment > from the block device to the loop device. With the exception of > discard_alignment, these parameters are visible via sysfs, discard_alignment is visible in sysfs, just not in the queue directory since alignment can be different on a per-partition basis. So there is one discard_alignment at the root of each /sys/block/foo directory and one for each partition subdirectory. This mirrors the alignment_offset variable which indicates a partitions alignment wrt. the underlying physical block size. That said, there are not many devices that actually report a non-zero discard alignment so it's not as useful as the device manufacturers (that were looking for an implementation shortcut) envisioned. > I'm not totally sure about discard_alignment, that seems to be useful > in cases of merging blk requests. So I can stop mirroring that one if > it's harmful or not helpful. But unless it's a nak, I'd really love to > keep most of the mirroring. In which case the bool doesn't do a whole > lot of simplifying. I think it's fine to export these. The block device topology was explicitly designed to be stackable like this. -- Martin K. Petersen Oracle Linux Engineering
