I hope this patch fixes the bug. If this patch fixes the problem
but has some problem about description or someone has better idea,
feel free to modify and resend to akpm, Please.

A full revert is overkill. Can the following patch be tested as a
potential replacement please?

---8<---
mm: compaction: Iron out isolate_freepages_block() and isolate_freepages_range() -fix1

CMA is reported to be broken in next-20120926. Minchan Kim pointed out
that this was due to nr_scanned != total_isolated in the case of CMA
because PageBuddy pages are one scan but many isolations in CMA. This
patch should address the problem.

This patch is a fix for
mm-compaction-acquire-the-zone-lock-as-late-as-possible-fix-2.patch

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 mm/compaction.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 8250b69..d6e260a 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c

@@ -282,6 +282,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
 {
 	int nr_scanned = 0, total_isolated = 0;
 	struct page *cursor, *valid_page = NULL;
+	unsigned long nr_strict_required = end_pfn - blockpfn;
 	unsigned long flags;
 	bool locked = false;
 

@@ -343,10 +344,10 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
 
 	/*
 	 * If strict isolation is requested by CMA then check that all the
-	 * pages scanned were isolated. If there were any failures, 0 is
+	 * pages requested were isolated. If there were any failures, 0 is
 	 * returned and CMA will fail.
 	 */
-	if (strict && nr_scanned != total_isolated)
+	if (strict && nr_strict_required != total_isolated)
 		total_isolated = 0;
 
 	if (locked)

--

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