diff options
| author | Laura Abbott <lauraa@codeaurora.org> | 2013-01-11 14:31:51 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-02-06 04:33:31 +0000 |
| commit | 458b03804988d061567a1a0f0d17c86967dfdc21 (patch) | |
| tree | 5406bc8a55c7ab1dd6f0b0ebaa24a6646e7df4f4 /mm | |
| parent | 2c7ff1aa06ba37b36e07d4b47c55d7431ec9dff9 (diff) | |
mm: use aligned zone start for pfn_to_bitidx calculation
commit c060f943d0929f3e429c5d9522290584f6281d6e upstream.
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.
For our use case, the effects of this bug were mostly tied to the fact
that CMA allocations would either take a long time or fail to happen.
Depending on the driver using CMA, this could result in anything from
visual glitches to application failures.
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_alloc.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a88dded3741..4d3a697a2e3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5532,7 +5532,7 @@ static inline int pfn_to_bitidx(struct zone *zone, unsigned long pfn) 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 */ } |