1 files changed, 56 insertions, 12 deletions

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 35d7e0ee1c77..3863acd6189c 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -17,6 +17,7 @@
 #include <linux/blkdev.h>
 #include <linux/pagevec.h>
 #include <linux/migrate.h>
+#include <linux/vmalloc.h>
 
 #include <asm/pgtable.h>
 
@@ -32,15 +33,8 @@ static const struct address_space_operations swap_aops = {
 #endif
 };
 
-struct address_space swapper_spaces[MAX_SWAPFILES] = {
-        [0 ... MAX_SWAPFILES - 1] = {
-                .page_tree      = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
-                .i_mmap_writable = ATOMIC_INIT(0),
-                .a_ops          = &swap_aops,
-                /* swap cache doesn't use writeback related tags */
-                .flags          = 1 << AS_NO_WRITEBACK_TAGS,
-        }
-};
+struct address_space *swapper_spaces[MAX_SWAPFILES];
+static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
 
 #define INC_CACHE_INFO(x)       do { swap_cache_info.x++; } while (0)
 
@@ -53,11 +47,26 @@ static struct {
 
 unsigned long total_swapcache_pages(void)
 {
-        int i;
+        unsigned int i, j, nr;
         unsigned long ret = 0;
+        struct address_space *spaces;
 
-        for (i = 0; i < MAX_SWAPFILES; i++)
-                ret += swapper_spaces[i].nrpages;
+        rcu_read_lock();
+        for (i = 0; i < MAX_SWAPFILES; i++) {
+                /*
+                 * The corresponding entries in nr_swapper_spaces and
+                 * swapper_spaces will be reused only after at least
+                 * one grace period.  So it is impossible for them
+                 * belongs to different usage.
+                 */
+                nr = nr_swapper_spaces[i];
+                spaces = rcu_dereference(swapper_spaces[i]);
+                if (!nr || !spaces)
+                        continue;
+                for (j = 0; j < nr; j++)
+                        ret += spaces[j].nrpages;
+        }
+        rcu_read_unlock();
         return ret;
 }
 
@@ -505,3 +514,38 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
 skip:
         return read_swap_cache_async(entry, gfp_mask, vma, addr);
 }
+
+int init_swap_address_space(unsigned int type, unsigned long nr_pages)
+{
+        struct address_space *spaces, *space;
+        unsigned int i, nr;
+
+        nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
+        spaces = vzalloc(sizeof(struct address_space) * nr);
+        if (!spaces)
+                return -ENOMEM;
+        for (i = 0; i < nr; i++) {
+                space = spaces + i;
+                INIT_RADIX_TREE(&space->page_tree, GFP_ATOMIC|__GFP_NOWARN);
+                atomic_set(&space->i_mmap_writable, 0);
+                space->a_ops = &swap_aops;
+                /* swap cache doesn't use writeback related tags */
+                mapping_set_no_writeback_tags(space);
+                spin_lock_init(&space->tree_lock);
+        }
+        nr_swapper_spaces[type] = nr;
+        rcu_assign_pointer(swapper_spaces[type], spaces);
+
+        return 0;
+}
+
+void exit_swap_address_space(unsigned int type)
+{
+        struct address_space *spaces;
+
+        spaces = swapper_spaces[type];
+        nr_swapper_spaces[type] = 0;
+        rcu_assign_pointer(swapper_spaces[type], NULL);
+        synchronize_rcu();
+        kvfree(spaces);
+}