Automount fails when accessing snapshots for root filesystem #9381
Comments
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@janlam7 thank you for reporting this. Would it be possible for you to verify this small patch resolves the issue? Unfortunately, I don't have a test system handy which uses ZFS for the root filesystem. diff --git a/module/os/linux/zfs/zfs_ctldir.c b/module/os/linux/zfs/zfs_ctldir.c
index 1e61ef0..3b2a6eb 100644
--- a/module/os/linux/zfs/zfs_ctldir.c
+++ b/module/os/linux/zfs/zfs_ctldir.c
@@ -1053,7 +1053,8 @@ zfsctl_snapshot_mount(struct path *path, int flags)
* on mount.zfs(8).
*/
snprintf(full_path, MAXPATHLEN, "%s/.zfs/snapshot/%s",
- zfsvfs->z_vfs->vfs_mntpoint, dname(dentry));
+ zfsvfs->z_vfs->vfs_mntpoint ? zfsvfs->z_vfs->vfs_mntpoint : "",
+ dname(dentry));
/*
* Multiple concurrent automounts of a snapshot are never allowed. |
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@behlendorf I ended up applying the patch below, and indeed it solves the issue, nice! I changed the paths to match the 0.8-release branch. |
Commit 093bb64 resolved an automount failures for chroot'd processes but inadvertently broke automounting for root filesystems where the vfs_mntpoint is NULL. Resolve the issue by checking for NULL in order to generate the correct path. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#9381
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The above patch does not seem to be enough for me. Even with it applied to zfs-0.8.2, snapshots under |
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I use initramfs created by dracut and openrc on the Funtoo distribution. |
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This issue got me as well. I too am using an initrd (though a homegrown one and not dracut). I can mount a snapshot with the following mount -t zfs pool/root@snap /mnt but the snapshot files under /.zfs/snapshots are all empty. |
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Running Devuan Ascii. Patch worked fine against Debian's 0.8.2-3. |
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@Ryushin do you use initramfs? |
Yes, I use Sysvinit and initramfs. I also tested on a Debian Buster system with sysvinit and initramfs as well. So it worked on both Devuan and Debian. |
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Seems I spoke too soon. Looks like I found a different kind of bug related to this. I've applied the patch listed above. My rpool looks like this: I can see inside snapshots for rpool/ROOT: Looking inside snapshots for any other dataset in rpool results in "Too many levels of symbolic links" error: |
Commit 093bb64 resolved an automount failures for chroot'd processes but inadvertently broke automounting for root filesystems where the vfs_mntpoint is NULL. Resolve the issue by checking for NULL in order to generate the correct path. Reviewed-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes openzfs#9381 Closes openzfs#9384
Commit 093bb64 resolved an automount failures for chroot'd processes but inadvertently broke automounting for root filesystems where the vfs_mntpoint is NULL. Resolve the issue by checking for NULL in order to generate the correct path. Reviewed-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes openzfs#9381 Closes openzfs#9384
Commit 093bb64 resolved an automount failures for chroot'd processes but inadvertently broke automounting for root filesystems where the vfs_mntpoint is NULL. Resolve the issue by checking for NULL in order to generate the correct path. Reviewed-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #9381 Closes #9384
* Now supports zfs versions that have the snapshot automount bug (openzfs/zfs#9381), as well as filesystems that are not mounted or have legacy mountpoints. * The recursive snapshot feature handles (skips) child objects that are not filesystems (but e.g. zvols). * We always leave the last successfully backed up snapshot (if any) intact, not the last snapshot as before. * No longer confused if the snapshot we're trying to create already exists (append numeric suffix to name). * Now supports recursive snapshots/backups of overlapping trees. * Share more code between recursive and nonrecursive snapshot case. * Switch to shared logging functions.
System information
Describe the problem you're observing
After upgrading from zfs-0.8.1 to zfs-0.8.2 the snapshots under the root filesystem do not automount anymore. I have my root on zfs. Snapshots below other filesystems automount normally.
The snapshots can be mounted manually, so I have a workaround.
Describe how to reproduce the problem
Include any warning/errors/backtraces from the system logs
I bisected it to commit 093bb64 in which case the following warning is logged in dmesg
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