On Wed 16-07-14 12:19:56, Johannes Weiner wrote: > 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. > > Properly uncharge the page after it's been migrated, including the > clearing of PCG_USED, so that a subsequent charge migration attempt > will be able to detect it and bail out. > > Signed-off-by: Johannes Weiner <[email protected]> > Reported-by: Hugh Dickins <[email protected]>
Acked-by: Michal Hocko <[email protected]> > --- > mm/memcontrol.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > Andrew, this replaces the patch of the same name in -mm. As Hugh > points out, we really have to clear PCG_USED of migrated pages, as > they are no longer pinning the memcg and so their pc->mem_cgroup can > no longer be trusted. > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 1e3b27f8dc2f..1439537fe7c9 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6655,7 +6655,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct > page *newpage, > > VM_BUG_ON_PAGE(!(pc->flags & PCG_MEM), oldpage); > VM_BUG_ON_PAGE(do_swap_account && !(pc->flags & PCG_MEMSW), oldpage); > - pc->flags &= ~(PCG_MEM | PCG_MEMSW); > > if (PageTransHuge(oldpage)) { > nr_pages <<= compound_order(oldpage); > @@ -6663,6 +6662,13 @@ void mem_cgroup_migrate(struct page *oldpage, struct > page *newpage, > VM_BUG_ON_PAGE(!PageTransHuge(newpage), newpage); > } > > + pc->flags = 0; > + > + local_irq_disable(); > + mem_cgroup_charge_statistics(pc->mem_cgroup, oldpage, -nr_pages); > + memcg_check_events(pc->mem_cgroup, oldpage); > + local_irq_enable(); > + > commit_charge(newpage, pc->mem_cgroup, nr_pages, lrucare); > } > > -- > 2.0.0 > -- Michal Hocko SUSE Labs -- 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/
