On Thu 29-10-20 22:25:26, Andrew Morton wrote:
> On Thu, 29 Oct 2020 14:11:03 +0100 Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> > On Thu 29-10-20 13:23:20, Nicholas Piggin wrote:
> > > Previously the negated unsigned long would be cast back to signed long
> > > which would have the correct negative value. After commit 730ec8c01a2b
> > > ("mm/vmscan.c: change prototype for shrink_page_list"), the large
> > > unsigned int converts to a large positive signed long.
> > >
> > > Symptoms include CMA allocations hanging forever holding the cma_mutex
> > > due to alloc_contig_range->...->isolate_migratepages_block waiting
> > > forever in "while (unlikely(too_many_isolated(pgdat)))".
> >
> > Nasty.
> >
> > > Cc: linux-mm@xxxxxxxxx
> > > Cc: Maninder Singh <maninder1.s@xxxxxxxxxxx>
> > > Cc: Vaneet Narang <v.narang@xxxxxxxxxxx>
> > > Cc: Maninder Singh <maninder1.s@xxxxxxxxxxx>
> > > Cc: Michal Hocko <mhocko@xxxxxxxx>
> > > Cc: Amit Sahrawat <a.sahrawat@xxxxxxxxxxx>
> > > Cc: Mel Gorman <mgorman@xxxxxxx>
> > > Cc: Vlastimil Babka <vbabka@xxxxxxx>
> > > Fixes: 730ec8c01a2b ("mm/vmscan.c: change prototype for shrink_page_list")
> > > Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> > > ---
> > > mm/vmscan.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > index 1b8f0e059767..92c507bacf09 100644
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -1516,7 +1516,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
> > > nr_reclaimed = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
> > > TTU_IGNORE_ACCESS, &stat, true);
> > > list_splice(&clean_pages, page_list);
> > > - mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -nr_reclaimed);
> > > + mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -(long)nr_reclaimed);
> > > /*
> > > * Since lazyfree pages are isolated from file LRU from the beginning,
> > > * they will rotate back to anonymous LRU in the end if it failed to
> >
> > You want the same also for -stat.nr_lazyfree_fail right?
>
> I did the below, and added a cc:stable.
>
> --- a/mm/vmscan.c~mm-vmscan-fix-nr_isolated_file-corruption-on-64-bit-fix
> +++ a/mm/vmscan.c
> @@ -1516,7 +1516,8 @@ unsigned int reclaim_clean_pages_from_li
> nr_reclaimed = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
> TTU_IGNORE_ACCESS, &stat, true);
> list_splice(&clean_pages, page_list);
> - mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -(long)nr_reclaimed);
> + mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
> + -(long)nr_reclaimed);
> /*
> * Since lazyfree pages are isolated from file LRU from the beginning,
> * they will rotate back to anonymous LRU in the end if it failed to
> @@ -1526,7 +1527,7 @@ unsigned int reclaim_clean_pages_from_li
> mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
> stat.nr_lazyfree_fail);
> mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
> - -stat.nr_lazyfree_fail);
> + -(long)stat.nr_lazyfree_fail);
> return nr_reclaimed;
> }
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Btw. regular reclaim paths are OK because nr_taken is unsigned long.
Btw #2 I was quite surprised about the inconsistency for !SMP case where
__mod_node_page_state uses int for the delta.
Thanks!
--
Michal Hocko
SUSE Labs
