From: Huang Ying <ying.huang@xxxxxxxxx> Subject: mm/swapfile.c: use swap_count() in swap_page_trans_huge_swapped() In swap_page_trans_huge_swapped(), to identify whether there's any page table mapping for a 4k sized swap entry, "si->swap_map[i] != SWAP_HAS_CACHE" is used. This works correctly now, because all users of the function will only call it after checking SWAP_HAS_CACHE. But as pointed out by Daniel, it is better to use "swap_count(map[i])" here, because it works for "map[i] == 0" case too. And this makes the implementation more consistent between normal and huge swap entry. Link: http://lkml.kernel.org/r/20180720071845.17920-4-ying.huang@xxxxxxxxx Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Suggested-and-reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Shaohua Li <shli@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/swapfile.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/swapfile.c~swap-use-swap_count-in-swap_page_trans_huge_swapped +++ a/mm/swapfile.c @@ -1429,12 +1429,12 @@ static bool swap_page_trans_huge_swapped ci = lock_cluster_or_swap_info(si, offset); if (!ci || !cluster_is_huge(ci)) { - if (map[roffset] != SWAP_HAS_CACHE) + if (swap_count(map[roffset])) ret = true; goto unlock_out; } for (i = 0; i < SWAPFILE_CLUSTER; i++) { - if (map[offset + i] != SWAP_HAS_CACHE) { + if (swap_count(map[offset + i])) { ret = true; break; } _
