The patch titled Subject: mm: use aligned zone start for pfn_to_bitidx calculation has been added to the -mm tree. Its filename is mm-use-aligned-zone-start-for-pfn_to_bitidx-calculation.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Laura Abbott <lauraa@xxxxxxxxxxxxxx> Subject: mm: use aligned zone start for pfn_to_bitidx calculation The current calculation in pfn_to_bitidx assumes that (pfn - zone->zone_start_pfn) >> pageblock_order will return the same bit for all pfn in a pageblock. If zone_start_pfn is not aligned to pageblock_nr_pages, this may not always be correct. Consider the following with pageblock order = 10, zone start 2MB: pfn | pfn - zone start | (pfn - zone start) >> page block order ---------------------------------------------------------------- 0x26000 | 0x25e00 | 0x97 0x26100 | 0x25f00 | 0x97 0x26200 | 0x26000 | 0x98 0x26300 | 0x26100 | 0x98 This means that calling {get,set}_pageblock_migratetype on a single page will not set the migratetype for the full block. Fix this by rounding down zone_start_pfn when doing the bitidx calculation. Signed-off-by: Laura Abbott <lauraa@xxxxxxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/page_alloc.c~mm-use-aligned-zone-start-for-pfn_to_bitidx-calculation mm/page_alloc.c --- a/mm/page_alloc.c~mm-use-aligned-zone-start-for-pfn_to_bitidx-calculation +++ a/mm/page_alloc.c @@ -5604,7 +5604,7 @@ static inline int pfn_to_bitidx(struct z pfn &= (PAGES_PER_SECTION-1); return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS; #else - pfn = pfn - zone->zone_start_pfn; + pfn = pfn - round_down(zone->zone_start_pfn, pageblock_nr_pages); return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS; #endif /* CONFIG_SPARSEMEM */ } _ Patches currently in -mm which might be from lauraa@xxxxxxxxxxxxxx are mm-use-aligned-zone-start-for-pfn_to_bitidx-calculation.patch debugging-keep-track-of-page-owners.patch debugging-keep-track-of-page-owners-fix.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html