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);
+}