1 files changed, 28 insertions, 21 deletions

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 85245fdec8d9..8368621a0fc7 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -73,23 +73,24 @@ unsigned long total_swapcache_pages(void)
 	unsigned int i, j, nr;
 	unsigned long ret = 0;
 	struct address_space *spaces;
+	struct swap_info_struct *si;
 
-	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)
+		swp_entry_t entry = swp_entry(i, 1);
+
+		/* Avoid get_swap_device() to warn for bad swap entry */
+		if (!swp_swap_info(entry))
+			continue;
+		/* Prevent swapoff to free swapper_spaces */
+		si = get_swap_device(entry);
+		if (!si)
 			continue;
+		nr = nr_swapper_spaces[i];
+		spaces = swapper_spaces[i];
 		for (j = 0; j < nr; j++)
 			ret += spaces[j].nrpages;
+		put_swap_device(si);
 	}
-	rcu_read_unlock();
 	return ret;
 }
 
@@ -310,8 +311,13 @@ struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
 			       unsigned long addr)
 {
 	struct page *page;
+	struct swap_info_struct *si;
 
+	si = get_swap_device(entry);
+	if (!si)
+		return NULL;
 	page = find_get_page(swap_address_space(entry), swp_offset(entry));
+	put_swap_device(si);
 
 	INC_CACHE_INFO(find_total);
 	if (page) {
@@ -354,8 +360,8 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 			struct vm_area_struct *vma, unsigned long addr,
 			bool *new_page_allocated)
 {
-	struct page *found_page, *new_page = NULL;
-	struct address_space *swapper_space = swap_address_space(entry);
+	struct page *found_page = NULL, *new_page = NULL;
+	struct swap_info_struct *si;
 	int err;
 	*new_page_allocated = false;
 
@@ -365,7 +371,12 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 		 * called after lookup_swap_cache() failed, re-calling
 		 * that would confuse statistics.
 		 */
-		found_page = find_get_page(swapper_space, swp_offset(entry));
+		si = get_swap_device(entry);
+		if (!si)
+			break;
+		found_page = find_get_page(swap_address_space(entry),
+					   swp_offset(entry));
+		put_swap_device(si);
 		if (found_page)
 			break;
 
@@ -601,20 +612,16 @@ int init_swap_address_space(unsigned int type, unsigned long nr_pages)
 		mapping_set_no_writeback_tags(space);
 	}
 	nr_swapper_spaces[type] = nr;
-	rcu_assign_pointer(swapper_spaces[type], spaces);
+	swapper_spaces[type] = spaces;
 
 	return 0;
 }
 
 void exit_swap_address_space(unsigned int type)
 {
-	struct address_space *spaces;
-
-	spaces = swapper_spaces[type];
+	kvfree(swapper_spaces[type]);
 	nr_swapper_spaces[type] = 0;
-	rcu_assign_pointer(swapper_spaces[type], NULL);
-	synchronize_rcu();
-	kvfree(spaces);
+	swapper_spaces[type] = NULL;
 }
 
 static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,