Date: Fri, 24 Nov 2023 08:16:54 -0800 From: Rick Macklem <rick.macklem@gmail.com> To: Mike Karels <mike@karels.net> Cc: Konstantin Belousov <kostikbel@gmail.com>, Alexander Leidinger <Alexander@leidinger.net>, Rick Macklem <rmacklem@freebsd.org>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: f5f277728ade - main - nfsd: Fix NFS access to .zfs/snapshot snapshots Message-ID: <CAM5tNy47MLeWdPEhV9LgVH84KB7Gmwpqmzxb62OET52Pn7pWJA@mail.gmail.com> In-Reply-To: <CAM5tNy5zLnDwxWuJ_u87k-c6WPwwp=MNjvDVto0=A9mwpyWc=g@mail.gmail.com> References: <202311231525.3ANFPBo6039293@gitrepo.freebsd.org> <987d4593d50b9cbffb9b6443d3825499@Leidinger.net> <ZWCe8k_lxWSpDA1L@kib.kiev.ua> <F4EB20B7-5AB8-4448-84BB-462BC7C37398@karels.net> <CAM5tNy5zLnDwxWuJ_u87k-c6WPwwp=MNjvDVto0=A9mwpyWc=g@mail.gmail.com>
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On Fri, Nov 24, 2023 at 7:58=E2=80=AFAM Rick Macklem <rick.macklem@gmail.co= m> wrote: > > On Fri, Nov 24, 2023 at 5:18=E2=80=AFAM Mike Karels <mike@karels.net> wro= te: > > > > CAUTION: This email originated from outside of the University of Guelph= . Do not click links or open attachments unless you recognize the sender an= d know the content is safe. If in doubt, forward suspicious emails to IThel= p@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=3Df5f277728adec4c5b3e8= 40a1fb16bd16f8cc956d > > >>> > > >>> commit f5f277728adec4c5b3e840a1fb16bd16f8cc956d > > >>> Author: Rick Macklem <rmacklem@FreeBSD.org> > > >>> AuthorDate: 2023-11-23 15:23:33 +0000 > > >>> Commit: Rick Macklem <rmacklem@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 sn= apshot. > > > > > > 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/snapsh= ot. > (As I understand it, there are non-default ZFS options that allow these t= o 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 nee= d 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 m= ay > not happen until the end of the year. > > If someone can test this case and determine if there is no NFS client acc= ess > 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. > >
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