[PATCH v3] mm: Enable suspend-only swap spaces

@@ -28,10 +28,11 @@ struct pagevec;
 #define SWAP_FLAG_DISCARD	0x10000 /* enable discard for swap */
 #define SWAP_FLAG_DISCARD_ONCE	0x20000 /* discard swap area at swapon-time */
 #define SWAP_FLAG_DISCARD_PAGES 0x40000 /* discard page-clusters after use */
+#define SWAP_FLAG_NOSWAP	0x80000 /* use only for hibernate, not swap */
 
 #define SWAP_FLAGS_VALID	(SWAP_FLAG_PRIO_MASK | SWAP_FLAG_PREFER | \
 				 SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | \
-				 SWAP_FLAG_DISCARD_PAGES)
+				 SWAP_FLAG_DISCARD_PAGES | SWAP_FLAG_NOSWAP)
 #define SWAP_BATCH 64
 
 static inline int current_is_kswapd(void)

@@ -182,6 +183,7 @@ enum {
 	SWP_PAGE_DISCARD = (1 << 10),	/* freed swap page-cluster discards */
 	SWP_STABLE_WRITES = (1 << 11),	/* no overwrite PG_writeback pages */
 	SWP_SYNCHRONOUS_IO = (1 << 12),	/* synchronous IO is efficient */
+	SWP_NOSWAP	= (1 << 13),	/* use only for suspend, not swap */
 					/* add others here before... */
 	SWP_SCANNING	= (1 << 14),	/* refcount in scan_swap_map */
 };

@@ -697,7 +697,8 @@ static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
 	if (si->inuse_pages == si->pages) {
 		si->lowest_bit = si->max;
 		si->highest_bit = 0;
-		del_from_avail_list(si);
+		if (!(si->flags & SWP_NOSWAP))
+			del_from_avail_list(si);
 	}
 }
 

@@ -726,10 +727,12 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
 		bool was_full = !si->highest_bit;
 
 		WRITE_ONCE(si->highest_bit, end);
-		if (was_full && (si->flags & SWP_WRITEOK))
+		if (was_full &&
+		    ((si->flags & (SWP_WRITEOK | SWP_NOSWAP)) == SWP_WRITEOK))
 			add_to_avail_list(si);
 	}
-	atomic_long_add(nr_entries, &nr_swap_pages);
+	if (!(si->flags & SWP_NOSWAP))
+		atomic_long_add(nr_entries, &nr_swap_pages);
 	si->inuse_pages -= nr_entries;
 	if (si->flags & SWP_BLKDEV)
 		swap_slot_free_notify =

@@ -1078,6 +1081,9 @@ int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
 			WARN(!(si->flags & SWP_WRITEOK),
 			     "swap_info %d in list but !SWP_WRITEOK\n",
 			     si->type);
+			WARN((si->flags & SWP_NOSWAP),
+			     "swap_info %d in list but SWP_NOSWAP\n",
+			     si->type);
 			__del_from_avail_list(si);
 			spin_unlock(&si->lock);
 			goto nextsi;

@@ -1338,8 +1344,12 @@ void swap_free(swp_entry_t entry)
 	struct swap_info_struct *p;
 
 	p = _swap_info_get(entry);
-	if (p)
-		__swap_entry_free(p, entry);
+	if (p) {
+		if (p->flags & SWP_NOSWAP)
+			swap_entry_free(p, entry);
+		else
+			__swap_entry_free(p, entry);
+	}
 }
 
 /*

@@ -1783,8 +1793,10 @@ swp_entry_t get_swap_page_of_type(int type)
 
 	/* This is called for allocating swap entry, not cache */
 	spin_lock(&si->lock);
-	if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
-		atomic_long_dec(&nr_swap_pages);
+	if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry)) {
+		if (!(si->flags & SWP_NOSWAP))
+			atomic_long_dec(&nr_swap_pages);
+	}
 	spin_unlock(&si->lock);
 fail:
 	return entry;

@@ -2454,8 +2466,6 @@ static void setup_swap_info(struct swap_info_struct *p, int prio,
 static void _enable_swap_info(struct swap_info_struct *p)
 {
 	p->flags |= SWP_WRITEOK;
-	atomic_long_add(p->pages, &nr_swap_pages);
-	total_swap_pages += p->pages;
 
 	assert_spin_locked(&swap_lock);
 	/*

@@ -2469,7 +2479,11 @@ static void _enable_swap_info(struct swap_info_struct *p)
 	 * swap_info_struct.
 	 */
 	plist_add(&p->list, &swap_active_head);
-	add_to_avail_list(p);
+	if (!(p->flags & SWP_NOSWAP)) {
+		atomic_long_add(p->pages, &nr_swap_pages);
+		total_swap_pages += p->pages;
+		add_to_avail_list(p);
+	}
 }
 
 static void enable_swap_info(struct swap_info_struct *p, int prio,

@@ -2564,7 +2578,9 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 		spin_unlock(&swap_lock);
 		goto out_dput;
 	}
-	del_from_avail_list(p);
+	if (!(p->flags & SWP_NOSWAP))
+		del_from_avail_list(p);
+
 	spin_lock(&p->lock);
 	if (p->prio < 0) {
 		struct swap_info_struct *si = p;

@@ -2581,8 +2597,10 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 		least_priority++;
 	}
 	plist_del(&p->list, &swap_active_head);
-	atomic_long_sub(p->pages, &nr_swap_pages);
-	total_swap_pages -= p->pages;
+	if (!(p->flags & SWP_NOSWAP)) {
+		atomic_long_sub(p->pages, &nr_swap_pages);
+		total_swap_pages -= p->pages;
+	}
 	p->flags &= ~SWP_WRITEOK;
 	spin_unlock(&p->lock);
 	spin_unlock(&swap_lock);

@@ -3335,16 +3353,20 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (swap_flags & SWAP_FLAG_PREFER)
 		prio =
 		  (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
+
+	if (swap_flags & SWAP_FLAG_NOSWAP)
+		p->flags |= SWP_NOSWAP;
 	enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map);
 
-	pr_info("Adding %uk swap on %s.  Priority:%d extents:%d across:%lluk %s%s%s%s%s\n",
+	pr_info("Adding %uk swap on %s.  Priority:%d extents:%d across:%lluk %s%s%s%s%s%s\n",
 		p->pages<<(PAGE_SHIFT-10), name->name, p->prio,
 		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
 		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
 		(p->flags & SWP_DISCARDABLE) ? "D" : "",
 		(p->flags & SWP_AREA_DISCARD) ? "s" : "",
 		(p->flags & SWP_PAGE_DISCARD) ? "c" : "",
-		(frontswap_map) ? "FS" : "");
+		(frontswap_map) ? "FS" : "",
+		(p->flags & SWP_NOSWAP) ? "N" : "");
 
 	mutex_unlock(&swapon_mutex);
 	atomic_inc(&proc_poll_event);