From: Huang Ying <ying.huang@xxxxxxxxx> Subject: swap: check mapping_empty() for swap cache before being freed To check whether all pages and shadow entries in swap cache has been removed before swap cache is freed. Link: https://lkml.kernel.org/r/20210608005121.511140-1-ying.huang@xxxxxxxxx Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Ilya Dryomov <idryomov@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/swap_state.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/mm/swap_state.c~swap-check-mapping_empty-for-swap-cache-before-being-freed +++ a/mm/swap_state.c @@ -693,7 +693,12 @@ int init_swap_address_space(unsigned int void exit_swap_address_space(unsigned int type) { - kvfree(swapper_spaces[type]); + int i; + struct address_space *spaces = swapper_spaces[type]; + + for (i = 0; i < nr_swapper_spaces[type]; i++) + VM_WARN_ON_ONCE(!mapping_empty(&spaces[i])); + kvfree(spaces); nr_swapper_spaces[type] = 0; swapper_spaces[type] = NULL; } _
