On Fri, Feb 17, 2006 at 01:00:17PM -0500, Jun'ichi Nomura wrote: > These patches provide common representation of dependencies > between stacked devices (dm and md) in sysfs. I'm neutral on this change so long as it can be done without introducing problems for device-mapper. > Though md0, dm-0, dm-1 and sd[a-d] contain same LVM2 meta data, > LVM2 should pick up md0 as PV, not dm-0, dm-1 and sdXs. > mdadm should build md0 from dm-0 and dm-1, not from sdXs. > Similar things will happen on 'mount' and 'fsck' if we use > file system labels instead of LVM2. I can't speak for the 'mount' code base, but I don't think it'll make any significant difference to LVM2 - we'd still have to do all the same device scanning as we do now because we have to be aware of md devices defined in on-disk metadata regardless of whether or not the kernel knows about them at the time the command is run. > Currently, these relationships are determined by each tool > combining information like the existence of md metadata > and dm dependency ioctl. And attempts to open a device exclusively. That's one check LVM2 does before running 'pvcreate' on a device. > thus we only need to check "holders" directory of the device > to decide whether the device is used by dm/md. > Also we can walk down the "slaves" directories to collect > the devices conposing the given dm/md device. For device-mapper devices, 'dmsetup deps' and ls --tree already gives you this information reasonably efficiently. Would others find the proposal useful for non-dm devices? And rather than adding code just to dm and md, would it be better to implement it by enhancing bd_claim()? Alasdair -- agk@xxxxxxxxxx -- dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
