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....) Cheers, Dan _______________________________________________ Dev mailing list -- dev@xxxxxxx To unsubscribe send an email to dev-leave@xxxxxxx
