Hugh reports: VM_BUG_ON_PAGE(!(pc->flags & PCG_MEM)) mm/memcontrol.c:6680! page had count 1 mapcount 0 mapping anon index 0x196 flags locked uptodate reclaim swapbacked, pcflags 1, memcg not root mem_cgroup_migrate < move_to_new_page < migrate_pages < compact_zone < compact_zone_order < try_to_compact_pages < __alloc_pages_direct_compact < __alloc_pages_nodemask < alloc_pages_vma < do_huge_pmd_anonymous_page < handle_mm_fault < __do_page_fault
mem_cgroup_migrate() assumes that a page is only migrated once and then freed immediately after. However, putting the page back on the LRU list and dropping the isolation refcount is not done atomically. This allows a PFN-based migrator like compaction to isolate the page, see the expected anonymous page refcount of 1, and migrate the page once more. Catch pages that have already been migrated and abort migration gracefully. Reported-by: Hugh Dickins <[email protected]> Signed-off-by: Johannes Weiner <[email protected]> --- mm/memcontrol.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1e3b27f8dc2f..e4afdbdda0a7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6653,7 +6653,10 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage, if (!PageCgroupUsed(pc)) return; - VM_BUG_ON_PAGE(!(pc->flags & PCG_MEM), oldpage); + /* Already migrated */ + if (!(pc->flags & PCG_MEM)) + return; + VM_BUG_ON_PAGE(do_swap_account && !(pc->flags & PCG_MEMSW), oldpage); pc->flags &= ~(PCG_MEM | PCG_MEMSW); -- 2.0.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
