On 16/08/2015 00:00, Ilya Dryomov wrote: > 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. > Excellent ! > Thanks, > > Ilya > -- Loïc Dachary, Artisan Logiciel Libre
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