Merge fixes from joyent/illumos-joyent

[ryao]

I found Joyent's repository on github and noticed that we are missing many key fixes that have been done. In particular, we are missing the following bug fixes:

TritonDataCenter/illumos-joyent@b46afb1
TritonDataCenter/illumos-joyent@7854499
TritonDataCenter/illumos-joyent@9dccfd2
TritonDataCenter/illumos-joyent@cf45ee4
TritonDataCenter/illumos-joyent@dccdc02

We also appear to be missing the following feature improvements:

TritonDataCenter/illumos-joyent@e9103aa
TritonDataCenter/illumos-joyent@19b94df

Brian, what are your thoughts about merging the bug fixes? In particular, I want to know if you want a single pull request for each or a monolithic pull request. How should copyright notice additions be handled? In addition, I would like your opinion on the usefulness of the improvements that are not bug fixes.

[ryao]

It was fairly easy to apply the bug fixes against ZFSOnLinux. I have opened pull requests for all of them. However, the feature improvements constitute a bit more work.

[behlendorf]

The bug fixes we of course need, opening a pull request for each was the right way to go about this. I'll review and test each of them and get them pulled in to our tree. This should be pretty straight forward since they're already passed several reviews for other distros. Thanks for doing the legwork to rebase these changes on the Linux tree.tained

As for the features we're going to need to take those on an individual basis. There are several outstanding features now in the various implementations we should probably evaluate. But for now I'm inclined to pull the change in only if it's considered low risk. That means either it's a relatively small and clear change. Or perhaps alternately its a change which is contained to some very specific part of the code and is unlikely to introduce problems.

[ryao]

It seems that TritonDataCenter/illumos-joyent@2ce93bc was a false positive. I have removed it from my original post.

[behlendorf]

@gentoofan Thanks for doing all the leg work on porting these bug fixes from Illumos, FreeBSD, and SmartOS. All of these OSs are under compatible licenses (BSD or CDDL) so there's no issue bring over the patches. In the highly unlikely event there is some sort of issue I like to keep each patch separate so they could be reverted easily if needed.

I've merged them in to master after reviewing and testing them. The only changes I really made were to rework the commit messages, historically when I've brought over changes I try to maintain as much history as possible about the change. Using that means:

• Preserving the original author with the --author git commit option
• Preserving the original commit comment (I wish they had better comments)
• Referencing the upstream issue when there is one
• Preserving all the original upstream reviews
• Crediting whomever ported the part
• The usual signed-off line for anyone who inspect it before it was merged in to the ZoL tree

Why don't we move the feature your ported to their own issues so they can be more easily tracked. Those are going to take some more care to review and can likely wait for a while since I haven't heard anyone asking for either of these features. Frankly I'm more concerned with getting the feature flag support in sooner rather than later.

[ryao]

Brian, thanks for detailed description of how you import fixes from other implementations. I will follow it in the future.