Date: Fri, 24 Nov 2023 07:58:58 -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: <CAM5tNy5zLnDwxWuJ_u87k-c6WPwwp=MNjvDVto0=A9mwpyWc=g@mail.gmail.com> In-Reply-To: <F4EB20B7-5AB8-4448-84BB-462BC7C37398@karels.net> References: <202311231525.3ANFPBo6039293@gitrepo.freebsd.org> <987d4593d50b9cbffb9b6443d3825499@Leidinger.net> <ZWCe8k_lxWSpDA1L@kib.kiev.ua> <F4EB20B7-5AB8-4448-84BB-462BC7C37398@karels.net>
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On Fri, Nov 24, 2023 at 5:18=E2=80=AFAM Mike Karels <mike@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 IThelp@= 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=3Df5f277728adec4c5b3e840= a1fb16bd16f8cc956d > >>> > >>> 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 mo= unted > >> 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-co= py > >> stuff enabled, but it doesn't work, as the jails can't access the snap= shot. > > > > 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. 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 wo= rk. 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 acces= s 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 m= ade > > to work usefully. >
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