Just to summarize... Mike Karels has done a simple test that works, so I don't know why my tests have misbehaved.
I will do some more tests in a few weeks. If you encounter problems accessing snapshots under .zfs/snapshot over NFS when you have added the patch in PR#275200, please post. rick On Fri, Nov 24, 2023 at 6:52 PM Rick Macklem <rick.mack...@gmail.com> wrote: > > On Fri, Nov 24, 2023 at 4:15 PM Rick Macklem <rick.mack...@gmail.com> wrote: > > > > On Fri, Nov 24, 2023 at 3:35 PM Rick Macklem <rick.mack...@gmail.com> wrote: > > > > > > On Fri, Nov 24, 2023 at 8:16 AM Rick Macklem <rick.mack...@gmail.com> > > > wrote: > > > > > > > > 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. > > > Yes, it is broken in a similar way. With a nullfs mount on top of a ZFS > > > mount > > > that is exported to an NFS client, you can access the snapshots under > > > .zfs/snapshot > > > if the mnt_exjail checks are commented out. > > > However, if the checks are done, they fail. > > > > > > So, yes, something similar to what ZFS will do is needed for nullfs. > > > Now I have to figure out how/when it can be done. I will play with it > > > to-day, > > > but it probably won't get fixed until late Dec. > > Oops. Now my test is not working, even when the mnt_exjail check is > > commented out. > > (When I NFS mount the ZFS <dataset>, I can see the snapshots under > > .zfs/snapshot, > > but when I NFS mount the nullfs mount that is on top of the ZFS > > <dataset> I do not see it. > > > > So, I think Kostik is correct and it does not see the .zfs/snapshot > > automount. > > > > I don't know how I screwed up on the first test after I disabled the > > mnt_exjail check, but > > it does not appear to have broken this case after all. > More info. Thanks to some off-list info from Mike Karels I tried it again. > It turns out that the nullfs on top of ZFS export (the nullfs mount must be > exported) sorta works. When you cd .zfs/snapshot/<snapshot-name>, it > works. > > What doesn't work is: > cd .zfs/snapshot > ls > --> which does not show the snapshot names > The snapshot names are shown for a mount of the ZFS file system. > > So, it seems that the Readdir has issues for a nullfs on top of ZFS > export for the .zfs/snapshot directory. I will poke at it some more > in late Dec., but it does not seem to be a problem related to mnt_exjail. > > rick > > > > > rick > > > > > > > > Again, sorry for the breakage, rick > > > > > > > > > > > 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. > > > > > >
