Hello, this series follows on the discussions of Joonsoo Kim's series "improve robustness on handling migratetype" https://lkml.org/lkml/2014/1/9/29 The goal is to close the race of get/set_pageblock_migratetype (and _skip) which Joonsoo found in the code and I've observed in my further compaction series development. Instead of a new seqlock for the pageblock bitmap, my series extends the coverage of zone->lock where possible (patch 1) and deals with the races where it's not feasible to lock (patches 2-4), as suggested by Mel in the original thread. Testing of patches 1-4 made me realize that a race between setting migratetype and set/clear_pageblock_skip is also an issue because all the 4 bits are packed within the same byte for each pair of pageblocks and the bit operations are not atomic. Thus and update to the skip bit may lose racing updates to some bits comprising migratetype and break it. Patch 5 reduces the amount of unneeded set_pageblock_skip calls, and patch 6 fixes the race by making the bit operations atomic, including reasons for picking this solution instead of using zone->lock also for set_pageblock_skip(). Vlastimil Vlastimil Babka (6): mm: call get_pageblock_migratetype() under zone->lock where possible mm: add get_pageblock_migratetype_nolock() for cases where locking is undesirable mm: add is_migrate_isolate_page_nolock() for cases where locking is undesirable mm: add set_pageblock_migratetype_nolock() for calls outside zone->lock mm: compaction: do not set pageblock skip bit when already set mm: use atomic bit operations in set_pageblock_flags_group() include/linux/mmzone.h | 24 +++++++++++++++ include/linux/page-isolation.h | 24 +++++++++++++++ mm/compaction.c | 18 ++++++++--- mm/hugetlb.c | 2 +- mm/memory-failure.c | 3 +- mm/page_alloc.c | 69 ++++++++++++++++++++++++++++-------------- mm/page_isolation.c | 23 ++++++++------ mm/vmstat.c | 2 +- 8 files changed, 126 insertions(+), 39 deletions(-) -- 1.8.4.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>