Hi Mel, On Thu, May 28, 2015 at 5:00 AM, Mel Gorman <mgorman@xxxxxxx> wrote: > On Wed, May 27, 2015 at 11:05:33AM -0700, Jovi Zhangwei wrote: >> Hi, >> >> I got below kernel bug error in our 3.18.13 stable kernel. >> "kernel BUG at mm/migrate.c:1661!" >> >> Source code: >> >> 1657 static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) >> 1658 { >> 1659 int page_lru; >> 1660 >> 1661 VM_BUG_ON_PAGE(compound_order(page) && >> !PageTransHuge(page), page); >> >> It's easy to trigger the error by run tcpdump in our system.(not sure >> it will easily be reproduced in another system) >> "sudo tcpdump -i bond0.100 'tcp port 4242' -c 100000000000 -w 4242.pcap" >> >> Any comments for this bug would be great appreciated. thanks. >> > > What sort of compound page is it? What sort of VMA is it in? hugetlbfs > pages should never be tagged for NUMA migrate and never enter this > path. Transparent huge pages are handled properly so I'm wondering > exactly what type of compound page this is and what mapped it into > userspace. > Thanks for your reply. After reading net/packet/af_packet.c:alloc_one_pg_vec_page, I found there indeed have compound page maped into userspace. I sent a patch for this issue(you may received it), but not sure it's right to fix, feel free to update it or use your own patch. Thanks. -------------------------------------------------------------------------------------------- [PATCH] mm/migrate: Avoid migrate mmaped compound pages Below kernel vm bug can be triggered by tcpdump which mmaped a lot of pages with GFP_COMP flag. [Mon May 25 05:29:33 2015] page:ffffea0015414000 count:66 mapcount:1 mapping: (null) index:0x0 [Mon May 25 05:29:33 2015] flags: 0x20047580004000(head) [Mon May 25 05:29:33 2015] page dumped because: VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page)) [Mon May 25 05:29:33 2015] ------------[ cut here ]------------ [Mon May 25 05:29:33 2015] kernel BUG at mm/migrate.c:1661! [Mon May 25 05:29:33 2015] invalid opcode: 0000 [#1] SMP The fix is simply disallow migrate mmaped compound pages, return 0 instead of report vm bug. Signed-off-by: Jovi Zhangwei <jovi.zhangwei@xxxxxxxxx> --- mm/migrate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/migrate.c b/mm/migrate.c index f53838f..839adef 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1606,7 +1606,8 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) { int page_lru; - VM_BUG_ON_PAGE(compound_order(page) && !PageTransHuge(page), page); + if (compound_order(page) && !PageTransHuge(page)) + return 0; /* Avoid migrating to a node that is nearly full */ if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page))) -- 1.9.1 -- 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>