Stop upgrade thread at the end of 'zfs recv'

[jxiong]

'zfs recv' could disown a living objset without calling

dmu_objset_disown(). This will cause the problem that the objset

would be released while upgrading thread is still running.



This patch calls dmu_objset_upgrade_stop() in dmu_recv_end().



ZoL-bug-id: #5295



Signed-off-by: Jinshan Xiong jinshan.xiong@intel.com

[mention-bot]

@jxiong, thanks for your PR! By analyzing the history of the files in this pull request, we identified @nedbass, @behlendorf and @ahrens to be potential reviewers.

[behlendorf]

@jxiong thanks for looking in to this. After looking at the fix a few questions come to mind.

1. zfs send/recv only operates on snapshots. Snapshots are immutable and thus can never be upgraded to include the quotaobj information. Given that it seems like the z_upgrade thread should be skipped them entirely so there would be no need to stop it as this patch does. We should perhaps make sure it's never started for this dataset.

2. Once all the snapshots are received there's the question of when the new filesystems should be automatically upgraded. This will automatically happen at next mount, but it may make sense to schedule it sooner at the end of zfs recv.

There was a strange build failure for CentOS 6, I've resubmitted that build to see if it's reproducible.

[jxiong]

@behlendorf it is a better solution by not triggering upgrade for snapshot, but ZFS_TYPE_SNAPSHOT is a ZPL layer information and I don't know how to access in DMU layer. What do you suggest?

2. Once all the ... of zfs recv.

Sorry I don't quite understand this - what does 'new file systems' refer to?

[behlendorf]

better solution by not triggering upgrade for snapshot. What do you suggest?

I was thinking either dmu_objset_is_snapshot() or dsl_dataset_is_snapshot().

what does 'new file systems' refer to?

Sorry this could have been worded better. I was just referring to the new dataset which can be mounted after receiving the snapshots. But since these will get automatically mounted anyway and thus owned that should trigger the upgrade. So I don't think we need to do anything extra. Nevermind 2) above.

[behlendorf]

Thanks for the quick patch! Nice and simple.