Commit f37d4298 authored Aug 06, 2014 by Andi Kleen Committed by Linus Torvalds Aug 06, 2014

hwpoison: fix race with changing page during offlining



When a hwpoison page is locked it could change state due to parallel
modifications.  The original compound page can be torn down and then
this 4k page becomes part of a differently-size compound page is is a
standalone regular page.

Check after the lock if the page is still the same compound page.

We could go back, grab the new head page and try again but it should be
quite rare, so I thought this was safest.  A retry loop would be more
difficult to test and may have more side effects.

The hwpoison code by design only tries to handle cases that are
reasonably common in workloads, as visible in page-flags.

I'm not really that concerned about handling this (likely rare case),
just not crashing on it.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent ad4404a2

mm/memory-failure.c

+10 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1172,6 +1172,16 @@ int memory_failure(unsigned long pfn, int trapno, int flags)

	lock_page(hpage);		lock_page(hpage);

			/*
			* The page could have changed compound pages during the locking.
			* If this happens just bail out.
			*/
			if (compound_head(p) != hpage) {
			action_result(pfn, "different compound page after locking", IGNORED);
			res = -EBUSY;
			goto out;
			}

	/*		/*
	* We use page flags to determine what action should be taken, but		* We use page flags to determine what action should be taken, but
	* the flags can be modified by the error containment action. One		* the flags can be modified by the error containment action. One

Admin message