HWPOISON 2.6.33 pre-merge posting

These are the hwpoison updates for 2.6.33
I plan to send the following patchkit to Linus in a few days. Any additional review would be appreciated.

Major new features:
- Be more aggressive at flushing caches to get access to a page
- Various fixes for the core memory_failure path
- Handle free memory better by detecting higher-order buddy pages reliably too.
- Reliable return value for memory_failure. This allows to implement some other functionality later on.
- New soft offlining feature:
Offline a page without killing a process.
This allows to implement predictive failure analysis for memory, by watching error trends per page and offlining a page that has too many corrected errors. The policy is all in user space; the kernel just offlines the page and reports the errors.
The current git mcelog has support for using this interface.
- Provide a new sysfs interface for both hard and soft offlining. The existing debugfs interface is still there.
- unpoison support
Unpoison a page. This is mainly for testing, it does not do unpoisioning on the hardware level.
- hwpoison filter
Various filters to the hwpoison PFN error injection, including memcg, page type, block device and others.
This is used by the mce-test stress suite to protect the test suite itself and

This touches some code outside hwpoison, mostly for the memcg support and for the page types. All these changes are straight-forward, are in linux-next and have been posted before.

-Andi