On Fri, Nov 24, 2023 at 7:58 AM Rick Macklem <rick.mack...@gmail.com> wrote: > > On Fri, Nov 24, 2023 at 5:18 AM Mike Karels <m...@karels.net> wrote: > > > > CAUTION: This email originated from outside of the University of Guelph. Do > > not click links or open attachments unless you recognize the sender and > > know the content is safe. If in doubt, forward suspicious emails to > > ith...@uoguelph.ca. > > > > > > On 24 Nov 2023, at 7:02, Konstantin Belousov wrote: > > > > > On Fri, Nov 24, 2023 at 08:50:22AM +0100, Alexander Leidinger wrote: > > >> Am 2023-11-23 16:25, schrieb Rick Macklem: > > >>> The branch main has been updated by rmacklem: > > >>> > > >>> URL: > > >>> https://cgit.FreeBSD.org/src/commit/?id=f5f277728adec4c5b3e840a1fb16bd16f8cc956d > > >>> > > >>> commit f5f277728adec4c5b3e840a1fb16bd16f8cc956d > > >>> Author: Rick Macklem <rmack...@freebsd.org> > > >>> AuthorDate: 2023-11-23 15:23:33 +0000 > > >>> Commit: Rick Macklem <rmack...@freebsd.org> > > >>> CommitDate: 2023-11-23 15:23:33 +0000 > > >>> > > >>> nfsd: Fix NFS access to .zfs/snapshot snapshots > > >>> > > >>> When a process attempts to access a snapshot under > > >>> /<dataset>/.zfs/snapshot, the snapshot is automounted. > > >>> However, without this patch, the automount does not > > >>> set mnt_exjail, which results in the snapshot not being > > >>> accessible over NFS. > > >>> > > >>> This patch defines a new function called vfs_exjail_clone() > > >>> which sets mnt_exjail from another mount point and > > >>> then uses that function to set mnt_exjail in the snapshot > > >>> automount. A separate patch that is currently a pull request > > >>> for OpenZFS, calls this function to fix the problem. > > >> > > >> May the same/similar fix like for ZFS be needed / useful for nullfs > > >> mounted > > >> stuff? > > >> > > >> I have a ZFS dataset which is mounted via nullfs into a jail. This > > >> nullfs-mount is then exported via samba. In samba I have the shadow-copy > > >> stuff enabled, but it doesn't work, as the jails can't access the > > >> snapshot. > > > > > > Jails cannot access snapshots because, as I understand, snapshots > > > are mounts. Nullfs does not provide an option to recursively bypass > > > into mounts. The patch you responded to does not automatically mounts > > > snapshots on clients, it only allows them to mount if wanted. > > > > It works for me, with main and this change, or 13.2 without a patch. > > I don't know the mechanics, but it doesn't use nullfs, and the snapshot > > does not show up as a separate filesystem with the mount command. > Yes. ZFS essentially does an automount of the snapshots under .zfs/snapshot. > (As I understand it, there are non-default ZFS options that allow these to be > mounted manually instead.) > I can now see that these automounts are 'real mounts" in the > mountlist. The only reason > they are not visible is that they have MNT_IGNORE set on them. Oh and I forgot to mention that this automount is for some weird in memory file system that does just enough so you can see the snapshots. Once you "cd <some-snapshot>", the vnodes are associated with the ZFS mount (dataset) and not this weird snapshot fs. (That is why it doesn't need to be exported, but did need mnt_exjail to be set properly.)
I might be able to test a nullfs over ZFS case later to-day and will post if I do so. rick > > Now, as for what happens when nullfs is on top of ZFS, I do not know. > What Kostik says about nullfs recursing into mounts suggests it will not work. > I will look at it, but since I am headed to Florida for a few weeks, it may > not happen until the end of the year. > > If someone can test this case and determine if there is no NFS client access > for snapshots under .zfs after applying the patch that is an > attachment in PR#275200 > when nullfs is over the ZFS file system, that would be appreciated. > > rick > > > > > Mike > > > > > You might try to set up something with autofs, no idea if it could be made > > > to work usefully. > >
