Support accessing .zfs/snapshot via NFS #2797
Conversation
|
@yshui Thanks for picking up the issue and helping push it forward. I'd love to get this functionality in place so lets start by sorting out the build failures and make sure all the automated testing passes. I like the fact that this pull request is broken up in to many logical changes with good comments. It makes the patch review easier. But could you please restructure the patch stack so that it builds on itself. Patches earlier in the stack should add the infrastructure needed by patches later in the stack. This is important because when the buildbot tests the patch it will test every commit in the stack and we want all those tests to pass. You can see the buildbot results in the details for this pull request. |
I was intended to do so, it seems I did it wrong... |
|
One more thing to be aware of. The buildbot uses the --enable-debug option to maximize test coverage. This also causes build warnings like the one below to be fatal. You'll need to address this and the style issues which were identified. |
|
The build failure on ubuntu-14.04 buildbot seems to be a problem in the bot itself. Soft lockup on buildbot ubuntu 13.10 is unrelated to this patch set. |
|
Right, don't worry about the 14.04 current builder results. It pretty closely tracks the latest kernel.org kernel and it appears they made an API change again. We'll need to sort that out. Other than that things looked pretty good. I'll get this reviewed. |
|
I wrote some simple code that uses lookup_one_len, and that doesn't seem to work. Don't know if it's because lookup_one_len doesn't trigger automount, or it's because I did something wrong. I'll read the code to make sure. |
|
@yshui I've looked at the code and |
|
@behlendorf lookup_one_len() uses __lookup_hash which doesn't seem to follow mounts. |
|
@yshui Yes, I see what you're saying. OK, thanks for investigating this may then be our cleanest option. Hopefully we'll get this for the next tag. |
|
Is it possible that in 0.6.3 accessing .zfs/snapshot via NFS worked but in 0.6.4 not? My tests show that in 0.6.3 I had access to snapshot via NFS, after upgrade to 0.6.4 from repository I lost access. |
|
@arturpzol No, this has never worked. Although, we expect to have it implemented for the official 0.6.4 tag using this patch stack. One of the very few remaining hold ups is additional testing of this patch stack. If you could try it out and report back that would be a great data point. |
|
@yshui I was just looking this over again to see if we can get it in for 0.6.4 and noticed you have fixsnap2 and fixsnap3 branch. It looks to me like fixsnap3 was the exploratory branch for using |
We could set MNT_SHRINKABLE when mouting snapshot mount instead of using occasional post mount getattr. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com> Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Prevents NFS client from detection of different fileids of snapshot root dentry before & after snapshot mount. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
There's no metadata to write to disk for ctldir inodes. So we check if a inode belongs to the ctldir in zpl_commit_metadata, and returns immediately if it is. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
When it's need to decode snapshot file handly it hard to get snapshot sb. On the contrary on snapshot mount it's easy to get snapshot sb because mount path available in the context of snapshot mount. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
We have to use long fids to include the dataset id. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
|
@behlendorf Yes, fixsnap3 is where I experimented with I have rebased this pull request. |
|
@yshui Thanks, I'm looking forward to getting the buildbot results. Personally, I'd really like to get this in. I assume you've been using it successfully for quite some time now. |
|
@yshui This looks like it's coming along nicely, I've made a few comments for issues I found while starting to test this. |
This will be used in later commit which add support for decoding snapshot fh. This is needed because in case the snapshot is not mounted when decoding its fh, we have to trigger an automount. And to trigger a snapshot automount, we have to know its path. In this commit we add a helper function which get the mount path from zpool and dataset properties (namely altroot and mountpoint properties). This is practically the same method used by the userspace zfs commandline tool. This method won't work for dataset with 'legacy' mountpoint, but we have to do it this way because newer Linux kernel hides the mount point information from file systems. Theoretically the proper solution of the problem is to eliminate the need to mount a snapshot, and just generate all snapshot related information on access. However this will require a lot more work and probably significant changes to how zfs handle snapshots. So I think we better leave this for later. Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
The snapshot file handle should provide enough info in order to get the right objsetid and right object in the objset defined by objsetid. Therefore we encode the snapshot fh as objsetid + inode. The objsetid should be encoded for every snapshot dentry including root dentry; for snapshot root dentry zf_gen should be 0. To decode a snapshot fh, we simply extract the objsetid and the inode, then we try to retrive the super block stored in the snapentry. Zero matching snapentry means the snapshot is not mounted. In this case we try to trigger a automount of the snapshot by doing a path lookup on the full snapshot path, and then try again. If zf_gen is 0, we return the snapshot root dentry. Also added a configure check for kern_path, since it is not available in earlier kernels. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com> Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
There's no metadata to write to disk for ctldir inodes. So we check if a inode belongs to the ctldir in zpl_commit_metadata, and returns immediately if it is. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#2797
There's no metadata to write to disk for ctldir inodes. So we check if a inode belongs to the ctldir in zpl_commit_metadata, and returns immediately if it is. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#2797
There's no metadata to write to disk for ctldir inodes. So we check if a inode belongs to the ctldir in zpl_commit_metadata, and returns immediately if it is. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#2797
This patch is based on the previous work done by @andrey-ve and @yshui. It triggers the automount by using kern_path() to traverse to the known snapshout mount point. Once the snapshot is mounted NFS can access the contents of the snapshot. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#2797 Issue openzfs#1655 Issue openzfs#616
|
Replaced by #3737. |
This patch is based on the previous work done by @andrey-ve and @yshui. It triggers the automount by using kern_path() to traverse to the known snapshout mount point. Once the snapshot is mounted NFS can access the contents of the snapshot. Allowing NFS clients to access to the .zfs/snapshot directory would normally mean that a root user on a client mounting an export with 'no_root_squash' would be able to use mkdir/rmdir/mv to manipulate snapshots on the server. To prevent configuration mistakes a zfs_admin_snapshot module option was added which disables the mkdir/rmdir/mv functionally. System administators desiring this functionally must explicitly enable it. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#2797 Issue openzfs#1655 Issue openzfs#616
This patch is based on the previous work done by @andrey-ve and @yshui. It triggers the automount by using kern_path() to traverse to the known snapshout mount point. Once the snapshot is mounted NFS can access the contents of the snapshot. Allowing NFS clients to access to the .zfs/snapshot directory would normally mean that a root user on a client mounting an export with 'no_root_squash' would be able to use mkdir/rmdir/mv to manipulate snapshots on the server. To prevent configuration mistakes a zfs_admin_snapshot module option was added which disables the mkdir/rmdir/mv functionally. System administators desiring this functionally must explicitly enable it. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes openzfs#2797 Closes openzfs#1655 Closes openzfs#616
There's no metadata to write to disk for ctldir inodes. So we check if a inode belongs to the ctldir in zpl_commit_metadata, and returns immediately if it is. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#2797
This patch is based on the previous work done by @andrey-ve and @yshui. It triggers the automount by using kern_path() to traverse to the known snapshout mount point. Once the snapshot is mounted NFS can access the contents of the snapshot. Allowing NFS clients to access to the .zfs/snapshot directory would normally mean that a root user on a client mounting an export with 'no_root_squash' would be able to use mkdir/rmdir/mv to manipulate snapshots on the server. To prevent configuration mistakes a zfs_admin_snapshot module option was added which disables the mkdir/rmdir/mv functionally. System administators desiring this functionally must explicitly enable it. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes openzfs#2797 Closes openzfs#1655 Closes openzfs#616
This patch is based on the previous work done by @andrey-ve and @yshui. It triggers the automount by using kern_path() to traverse to the known snapshout mount point. Once the snapshot is mounted NFS can access the contents of the snapshot. Allowing NFS clients to access to the .zfs/snapshot directory would normally mean that a root user on a client mounting an export with 'no_root_squash' would be able to use mkdir/rmdir/mv to manipulate snapshots on the server. To prevent configuration mistakes a zfs_admin_snapshot module option was added which disables the mkdir/rmdir/mv functionally. System administators desiring this functionally must explicitly enable it. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes openzfs#2797 Closes openzfs#1655 Closes openzfs#616
There's no metadata to write to disk for ctldir inodes. So we check if a inode belongs to the ctldir in zpl_commit_metadata, and returns immediately if it is. Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#2797
Since @andrey-ve has been quiet recently, I decide to step up to address the remaining issues in his patchset (#1655).
I have re-organized the commits and re-phrased some of the commit log. For those commits I changed, I have appended my signed-off line to them.
Please review, thanks.