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Subject[PATCH] swap: Check mapping_empty() for swap cache before being freed
Date
To check whether all pages and shadow entries in swap cache has been
removed before swap cache is freed.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ilya Dryomov <idryomov@gmail.com>
---

BTW: The patch reverts the following patch in -mm tree in effect.

mm/swap: remove unused global variable nr_swapper_spaces

---
mm/swap_state.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 95e391f46468..c56aa9ac050d 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -37,6 +37,7 @@ static const struct address_space_operations swap_aops = {
};

struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
+static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
static bool enable_vma_readahead __read_mostly = true;

#define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2)
@@ -684,6 +685,7 @@ int init_swap_address_space(unsigned int type, unsigned long nr_pages)
/* swap cache doesn't use writeback related tags */
mapping_set_no_writeback_tags(space);
}
+ nr_swapper_spaces[type] = nr;
swapper_spaces[type] = spaces;

return 0;
@@ -691,7 +693,13 @@ int init_swap_address_space(unsigned int type, unsigned long nr_pages)

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;
}

--
2.30.2
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