1 files changed, 27 insertions, 5 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 235c039892ee..a3e22d357e91 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -202,6 +202,18 @@ struct swap_info_struct {
         unsigned long *frontswap_map;   /* frontswap in-use, one bit per page */
         atomic_t frontswap_pages;       /* frontswap pages in-use counter */
 #endif
+        spinlock_t lock;                /*
+                                         * protect map scan related fields like
+                                         * swap_map, lowest_bit, highest_bit,
+                                         * inuse_pages, cluster_next,
+                                         * cluster_nr, lowest_alloc and
+                                         * highest_alloc. other fields are only
+                                         * changed at swapon/swapoff, so are
+                                         * protected by swap_lock. changing
+                                         * flags need hold this lock and
+                                         * swap_lock. If both locks need hold,
+                                         * hold swap_lock first.
+                                         */
 };
 
 struct swap_list_t {
@@ -209,9 +221,6 @@ struct swap_list_t {
         int next;       /* swapfile to be used next */
 };
 
-/* Swap 50% full? Release swapcache more aggressively.. */
-#define vm_swap_full() (nr_swap_pages*2 < total_swap_pages)
-
 /* linux/mm/page_alloc.c */
 extern unsigned long totalram_pages;
 extern unsigned long totalreserve_pages;
@@ -347,8 +356,20 @@ extern struct page *swapin_readahead(swp_entry_t, gfp_t,
                         struct vm_area_struct *vma, unsigned long addr);
 
 /* linux/mm/swapfile.c */
-extern long nr_swap_pages;
+extern atomic_long_t nr_swap_pages;
 extern long total_swap_pages;
+
+/* Swap 50% full? Release swapcache more aggressively.. */
+static inline bool vm_swap_full(void)
+{
+        return atomic_long_read(&nr_swap_pages) * 2 < total_swap_pages;
+}
+
+static inline long get_nr_swap_pages(void)
+{
+        return atomic_long_read(&nr_swap_pages);
+}
+
 extern void si_swapinfo(struct sysinfo *);
 extern swp_entry_t get_swap_page(void);
 extern swp_entry_t get_swap_page_of_type(int);
@@ -381,9 +402,10 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
 
 #else /* CONFIG_SWAP */
 
-#define nr_swap_pages                           0L
+#define get_nr_swap_pages()                     0L
 #define total_swap_pages                        0L
 #define total_swapcache_pages()                 0UL
+#define vm_swap_full()                          0
 
 #define si_swapinfo(val) \
         do { (val)->freeswap = (val)->totalswap = 0; } while (0)