On Sat, Aug 15, 2015 at 11:56 PM, Loic Dachary <loic@xxxxxxxxxxx> wrote: > Hi Ilya, > > On 15/08/2015 19:42, Ilya Dryomov wrote: >> On Sat, Aug 15, 2015 at 6:35 PM, Loic Dachary <loic@xxxxxxxxxxx> wrote: >>> Hi Sage, >>> >>> On 15/08/2015 16:28, Sage Weil wrote: >>>> On Sat, 15 Aug 2015, Loic Dachary wrote: >>>>> Hi, >>>>> >>>>> Is there a portable and consistent way to figure out if a given /dev/XXX >>>>> path (for instance /dev/dm-1) is a partition of a whole device ? >>>>> Although checking /sys/block/dm-1/dm/name for a number at the end (like >>>>> mpatha1 or mpatha2) would probably work, it feels like a fragile hack. >>>>> Looking into /sys/block/dm-1/slaves will lead to >>>>> /sys/block/dm-1/slaves/dm-0 and we can check that >>>>> /sys/block/dm-*/subsystem is class/block. But that does not necessarily >>>>> mean dm-1 is a partition of dm-0, just that it's a slave of dm-0. >>>> >>>> Take a look at is_partition in ceph-disk, whih is the best I came up with. >>>> Basically it checks if the device name appears as /sys/block/*/$foo... >> >> For regular devices, you can access() /sys/dev/block/maj:min/partition. >> If it's there, it's a partition - no need to iterate over /sys/block. > > I added http://tracker.ceph.com/issues/12706 for when someone has time to rework that part of the code. > >> >>> >>> That is consistently updated for /dev/sdb or /dev/vdb but things are different when using multipath. I'll rely on /sys/block/dm-?/dm/name instead until a better solution is found. >> >> A better way might be to rely on the fact that a dm partition will >> necessarily have its uuid prefixed by "part". In that case, it should >> be safe to assume that the thing in slaves is a whole disk - I think >> that's what various util-linux tools do. However, IIRC the dm uuid is >> optional, so that won't work on a dm device without a uuid. > > It looks like multipath on both CentOS 7 and Ubuntu 14.04 set the uuid in this way. > > Is it also safe to assume that if the uuid is: > > $ cat /sys/dev/block/253:?/dm/uuid > mpath-353333330000007d0 > part1-mpath-353333330000007d0 > part2-mpath-353333330000007d0 > > it means these were created by multipath because of the mpath ? When asking dmsetup with: Yes, I think so. I'm pretty sure these "part<id>-" and "mpath-" prefixes were devised for exactly this purpose. Thanks, Ilya -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
