Re: [PATCH] mm/vmscan: Fix NR_ISOLATED_FILE corruption on 64-bit

[Michal Hocko <mhocko@suse.com>]

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@kvack.org
> Cc: Maninder Singh <maninder1.s@samsung.com>
> Cc: Vaneet Narang <v.narang@samsung.com>
> Cc: Maninder Singh <maninder1.s@samsung.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Amit Sahrawat <a.sahrawat@samsung.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Fixes: 730ec8c01a2b ("mm/vmscan.c: change prototype for shrink_page_list")
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  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?

-- 
Michal Hocko
SUSE Labs