> Actually, looking at it some more, I think that two-liner patch had > *ANOTHER* bug. > > Because the other line seems buggy as well. > > Instead of > > end_pfn = ALIGN(pfn + pageblock_nr_pages, pageblock_nr_pages); > > I think it should be > > end_pfn = ALIGN(pfn+1, pageblock_nr_pages); > > instead. ALIGN() already aligns upwards (but the "+1" is needed in > case pfn is already at a pageblock_nr_pages boundary, at which point > ALIGN() would have just returned that same boundary. Ah, and now the two callers treat the pointers the same way. > Hmm? Mel, please confirm. And Henrik, it might be good to test that > doubly-fixed patch. Because reading the patch and trying to fix bugs > in it that way is *not* the same as actually verifying it ;) Confirmed, working. I also checked 3.6, but could not trigger the original problem there. The code also looks different, so it makes sense. To be explicit, this is what I tested on top of v3.7-rc8: --- mm/compaction.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index 9eef558..ff1c483 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -713,7 +713,15 @@ static void isolate_freepages(struct zone *zone, /* Found a block suitable for isolating free pages from */ isolated = 0; - end_pfn = min(pfn + pageblock_nr_pages, zone_end_pfn); + + /* + * As pfn may not start aligned, pfn+pageblock_nr_page + * may cross a MAX_ORDER_NR_PAGES boundary and miss + * a pfn_valid check. Ensure isolate_freepages_block() + * only scans within a pageblock. + */ + end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); + end_pfn = min(end_pfn, zone_end_pfn); isolated = isolate_freepages_block(cc, pfn, end_pfn, freelist, false); nr_freepages += isolated; -- 1.8.0.1 Hopefully, that's a wrap. :-) Henrik -- 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>