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authorMel Gorman <mgorman@suse.de>2013-02-22 16:32:25 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-23 17:50:10 -0800
commita9aacbccf3145355190d87f0df1731fb84fdd8c8 (patch)
tree52ac31c9be66f8114b3bff314fdc0802fce98f83 /mm/compaction.c
parent62b726c1b3cde6ab49304e8c1af41950ed855c3c (diff)
downloadlinux-a9aacbccf3145355190d87f0df1731fb84fdd8c8.tar.gz
mm: compaction: do not accidentally skip pageblocks in the migrate scanner
Compaction uses the ALIGN macro incorrectly with the migrate scanner by adding pageblock_nr_pages to a PFN. It happened to work when initially implemented as the starting PFN was also aligned but with caching restarts and isolating in smaller chunks this is no longer always true. The impact is that the migrate scanner scans outside its current pageblock. As pfn_valid() is still checked properly it does not cause any failure and the impact of the bug is that in some cases it will scan more than necessary when it crosses a page boundary but by no more than COMPACT_CLUSTER_MAX. It is highly unlikely this is even measurable but it's still wrong so this patch addresses the problem. Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/compaction.c')
-rw-r--r--mm/compaction.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index c62bd063d76..0d0248db36d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -611,8 +611,7 @@ check_compact_cluster:
continue;
next_pageblock:
- low_pfn += pageblock_nr_pages;
- low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
+ low_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages) - 1;
last_pageblock_nr = pageblock_nr;
}
@@ -795,7 +794,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
/* Only scan within a pageblock boundary */
- end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
+ end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
/* Do not cross the free scanner or scan within a memory hole */
if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {