Implement epoll support in Linuxulator (committed, then reverted changeset)

[koobs]

Summary

Previous discussions on IRC have highlighted that this code requires review & polish. Champions are needed from Team Src to help usher this almost complete change back into base. Highly valuable for us in upcoming releases in combination with Linux base upgrades and end-user application support/compatibility.

People who interacted with this changeset or post-commit-discussion have been added as Reviewers/Subscribers. If you cannot assist with review, please callout to people who may be able to.

Originally Committed in: http://svnweb.freebsd.org/base?view=revision&revision=255672
Reverted in: http://svnweb.freebsd.org/base?view=revision&revision=255675
svn-src-head thread: http://lists.freebsd.org/pipermail/svn-src-head/2014-May/058194.html

Original Commit Log:

Implement epoll support in Linuxulator. This is a tiny wrapper around kqueue
to implement epoll subset of functionality. The kqueue user data are 32bit
on i386 which is not enough for epoll user data so this patch overrides
kqueue fileops to maintain enough space in struct file.

Initial patch developed by me in 2007 and then extended and finished
by Yuri Victorovich.

Approved by: re (delphij)
Sponsored by: Google Summer of Code
Submitted by: Yuri Victorovich <yuri at rawbw dot com>
Tested by: Yuri Victorovich <yuri at rawbw dot com>

[dchagin]

First of all i do not understand how it works. See r227070, r232702.
Secondly, if this is so important I will try to merge a set of commits about epoll from lemul branch.
Anyway, I strongly object to commit this.

[dim]

I guess I was put on the reviewers list, because I'm also called D(i)mitry :), but anyway: I think there is no rush to get this into head quickly, since there is no way this will make it into 9.3 at this time, 9.3 is basically in feature freeze. And if it conflicts with dchagin's work on his linuxolator branch, it is even more disruptive....

[delphij]

I think I'm not a proper reviewer for this one.

(By the way, the kern_utimensat seems to be unrelated, probably leaked change?)

[dchagin]

Done in lemul, so remove from Active Revisions