On Sat, Apr 2, 2022 at 1:01 AM Dan van der Ster <dvanders@xxxxxxxxx> wrote: > > Hi Venky and CephFS devs, > > Are you aware of problems with long snapshot names? > > The Manila driver creates pretty long subvolume snapshot names: > https://github.com/openstack/manila/blob/master/manila/share/drivers/cephfs/driver.py#L566-L580 > Ex: 3c42f809-4b10-4877-911d-c68910747ae5_eb90c527-9de4-4f57-87bf-6b06f57a396c > > And we have trouble accessing those. > > It works with a recent kernel this way: > > # ls /cephfs-pam-fuse/volumes/_nogroup/dbebbb35-31f1-47e5-ac75-48d65a1ee33c/.snap/3c42f809-4b10-4877-911d-c68910747ae5_eb90c527-9de4-4f57-87bf-6b06f57a396c/fe1b97f3-3481-43a9-a677-c9424544de09/ > now > # > > But we cannot see the "now" file when listing via .snap in a subdir: > > # ls /cephfs-pam-fuse/volumes/_nogroup/dbebbb35-31f1-47e5-ac75-48d65a1ee33c/fe1b97f3-3481-43a9-a677-c9424544de09/.snap/_3c42f809-4b10-4877-911d-c68910747ae5_eb90c527-9de4-4f57-87bf-6b06f57a396c_1100/ > # > > (Subvolume_V2 users always mount the subdir, so they can only ever > access snaps via the subdir path, btw). > > The kernel client has the same issue (confirmed with latest CentOS > Stream 8 kernel). > > And btw old kernels can't even list this dir. Here is the latest > CentOS 7 kernel: > > # ls /cephfs-pam/volumes/_nogroup/dbebbb35-31f1-47e5-ac75-48d65a1ee33c/fe1b97f3-3481-43a9-a677-c9424544de09/.snap/ > ls: cannot access > /cephfs-pam/volumes/_nogroup/dbebbb35-31f1-47e5-ac75-48d65a1ee33c/fe1b97f3-3481-43a9-a677-c9424544de09/.snap/_3c42f809-4b10-4877-911d-c68910747ae5_eb90c527-9de4-4f57-87bf-6b06f57a396c_1100: > No such file or directory > _3c42f809-4b10-4877-911d-c68910747ae5_eb90c527-9de4-4f57-87bf-6b06f57a396c_1100 > > > I think this is all because the snap name is too long. > Notice that the subdir snap has _1100 appended -- this is supposed to > be the inode of the place where the snap was taken (IIUC) -- but it > has been truncated to 80 chars, presumably because of > https://github.com/ceph/ceph/blob/master/src/mds/snap.cc#L87 > > We have snaps in subvolumes with shorter names -- they work perfectly. > And anyway surely someone would have noticed if subvolume snapshots > are completely unusable, right?! > > Do we have a limit (not enforced) on CephFS snapshot names? > Should we enforce that? (IIUC the user definable length should be 14 > or 15 chars fewer than 80, let's say 64 to be safe?) > If you agree with this all we'll send a PR to Manila too for a quick > fix. (I can't believe no one has tried this....) We (obviously) require the two PRs Xiubo mentioned and backported. And I think adding an input length guard in Manila seems right for cases where a version of Ceph is used which does not have the MDS fix. > > Cheers, Dan > -- Cheers, Venky _______________________________________________ Dev mailing list -- dev@xxxxxxx To unsubscribe send an email to dev-leave@xxxxxxx
