mm: memcontrol: consolidate swap controller code

The swap controller code is scattered all over the file. Gather all
the code that isn't directly needed by the memory controller at the
end of the file in its own CONFIG_MEMCG_SWAP section.

Signed-off-by: Johannes Weiner <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Reviewed-by: Vladimir Davydov <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/memcontrol.c

···
 #define MEM_CGROUP_RECLAIM_RETRIES	5
 static struct mem_cgroup *root_mem_cgroup __read_mostly;
 
+/* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP
-/* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
 int do_swap_account __read_mostly;
-
-/* for remember boot option*/
-#ifdef CONFIG_MEMCG_SWAP_ENABLED
-static int really_do_swap_account __initdata = 1;
-#else
-static int really_do_swap_account __initdata;
-#endif
-
 #else
 #define do_swap_account		0
 #endif
-
 
 static const char * const mem_cgroup_stat_names[] = {
 	"cache",
···
 	{ },	/* terminate */
 };
 
-#ifdef CONFIG_MEMCG_SWAP
-static struct cftype memsw_cgroup_files[] = {
-	{
-		.name = "memsw.usage_in_bytes",
-		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
-		.read_u64 = mem_cgroup_read_u64,
-	},
-	{
-		.name = "memsw.max_usage_in_bytes",
-		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
-		.write = mem_cgroup_reset,
-		.read_u64 = mem_cgroup_read_u64,
-	},
-	{
-		.name = "memsw.limit_in_bytes",
-		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
-		.write = mem_cgroup_write,
-		.read_u64 = mem_cgroup_read_u64,
-	},
-	{
-		.name = "memsw.failcnt",
-		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
-		.write = mem_cgroup_reset,
-		.read_u64 = mem_cgroup_read_u64,
-	},
-	{ },	/* terminate */
-};
-#endif
 static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
 {
 	struct mem_cgroup_per_node *pn;
···
 	.early_init = 0,
 };
 
-#ifdef CONFIG_MEMCG_SWAP
-static int __init enable_swap_account(char *s)
-{
-	if (!strcmp(s, "1"))
-		really_do_swap_account = 1;
-	else if (!strcmp(s, "0"))
-		really_do_swap_account = 0;
-	return 1;
-}
-__setup("swapaccount=", enable_swap_account);
-
-static void __init memsw_file_init(void)
-{
-	WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys,
-					  memsw_cgroup_files));
-}
-
-static void __init enable_swap_cgroup(void)
-{
-	if (!mem_cgroup_disabled() && really_do_swap_account) {
-		do_swap_account = 1;
-		memsw_file_init();
-	}
-}
-
-#else
-static void __init enable_swap_cgroup(void)
-{
-}
-#endif
-
 /**
  * mem_cgroup_events - count memory events against a cgroup
  * @memcg: the memory cgroup
···
 	}
 	return true;
 }
-
-#ifdef CONFIG_MEMCG_SWAP
-/**
- * mem_cgroup_swapout - transfer a memsw charge to swap
- * @page: page whose memsw charge to transfer
- * @entry: swap entry to move the charge to
- *
- * Transfer the memsw charge of @page to @entry.
- */
-void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
-{
-	struct mem_cgroup *memcg;
-	unsigned short oldid;
-
-	VM_BUG_ON_PAGE(PageLRU(page), page);
-	VM_BUG_ON_PAGE(page_count(page), page);
-
-	if (!do_swap_account)
-		return;
-
-	memcg = page->mem_cgroup;
-
-	/* Readahead page, never charged */
-	if (!memcg)
-		return;
-
-	oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg));
-	VM_BUG_ON_PAGE(oldid, page);
-	mem_cgroup_swap_statistics(memcg, true);
-
-	page->mem_cgroup = NULL;
-
-	if (!mem_cgroup_is_root(memcg))
-		page_counter_uncharge(&memcg->memory, 1);
-
-	/* XXX: caller holds IRQ-safe mapping->tree_lock */
-	VM_BUG_ON(!irqs_disabled());
-
-	mem_cgroup_charge_statistics(memcg, page, -1);
-	memcg_check_events(memcg, page);
-}
-
-/**
- * mem_cgroup_uncharge_swap - uncharge a swap entry
- * @entry: swap entry to uncharge
- *
- * Drop the memsw charge associated with @entry.
- */
-void mem_cgroup_uncharge_swap(swp_entry_t entry)
-{
-	struct mem_cgroup *memcg;
-	unsigned short id;
-
-	if (!do_swap_account)
-		return;
-
-	id = swap_cgroup_record(entry, 0);
-	rcu_read_lock();
-	memcg = mem_cgroup_lookup(id);
-	if (memcg) {
-		if (!mem_cgroup_is_root(memcg))
-			page_counter_uncharge(&memcg->memsw, 1);
-		mem_cgroup_swap_statistics(memcg, false);
-		css_put(&memcg->css);
-	}
-	rcu_read_unlock();
-}
-#endif
 
 /**
  * mem_cgroup_try_charge - try charging a page
···
 		soft_limit_tree.rb_tree_per_node[node] = rtpn;
 	}
 
-	enable_swap_cgroup();
-
 	return 0;
 }
 subsys_initcall(mem_cgroup_init);
+
+#ifdef CONFIG_MEMCG_SWAP
+/**
+ * mem_cgroup_swapout - transfer a memsw charge to swap
+ * @page: page whose memsw charge to transfer
+ * @entry: swap entry to move the charge to
+ *
+ * Transfer the memsw charge of @page to @entry.
+ */
+void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
+{
+	struct mem_cgroup *memcg;
+	unsigned short oldid;
+
+	VM_BUG_ON_PAGE(PageLRU(page), page);
+	VM_BUG_ON_PAGE(page_count(page), page);
+
+	if (!do_swap_account)
+		return;
+
+	memcg = page->mem_cgroup;
+
+	/* Readahead page, never charged */
+	if (!memcg)
+		return;
+
+	oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg));
+	VM_BUG_ON_PAGE(oldid, page);
+	mem_cgroup_swap_statistics(memcg, true);
+
+	page->mem_cgroup = NULL;
+
+	if (!mem_cgroup_is_root(memcg))
+		page_counter_uncharge(&memcg->memory, 1);
+
+	/* XXX: caller holds IRQ-safe mapping->tree_lock */
+	VM_BUG_ON(!irqs_disabled());
+
+	mem_cgroup_charge_statistics(memcg, page, -1);
+	memcg_check_events(memcg, page);
+}
+
+/**
+ * mem_cgroup_uncharge_swap - uncharge a swap entry
+ * @entry: swap entry to uncharge
+ *
+ * Drop the memsw charge associated with @entry.
+ */
+void mem_cgroup_uncharge_swap(swp_entry_t entry)
+{
+	struct mem_cgroup *memcg;
+	unsigned short id;
+
+	if (!do_swap_account)
+		return;
+
+	id = swap_cgroup_record(entry, 0);
+	rcu_read_lock();
+	memcg = mem_cgroup_lookup(id);
+	if (memcg) {
+		if (!mem_cgroup_is_root(memcg))
+			page_counter_uncharge(&memcg->memsw, 1);
+		mem_cgroup_swap_statistics(memcg, false);
+		css_put(&memcg->css);
+	}
+	rcu_read_unlock();
+}
+
+/* for remember boot option*/
+#ifdef CONFIG_MEMCG_SWAP_ENABLED
+static int really_do_swap_account __initdata = 1;
+#else
+static int really_do_swap_account __initdata;
+#endif
+
+static int __init enable_swap_account(char *s)
+{
+	if (!strcmp(s, "1"))
+		really_do_swap_account = 1;
+	else if (!strcmp(s, "0"))
+		really_do_swap_account = 0;
+	return 1;
+}
+__setup("swapaccount=", enable_swap_account);
+
+static struct cftype memsw_cgroup_files[] = {
+	{
+		.name = "memsw.usage_in_bytes",
+		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
+		.read_u64 = mem_cgroup_read_u64,
+	},
+	{
+		.name = "memsw.max_usage_in_bytes",
+		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
+		.write = mem_cgroup_reset,
+		.read_u64 = mem_cgroup_read_u64,
+	},
+	{
+		.name = "memsw.limit_in_bytes",
+		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
+		.write = mem_cgroup_write,
+		.read_u64 = mem_cgroup_read_u64,
+	},
+	{
+		.name = "memsw.failcnt",
+		.private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
+		.write = mem_cgroup_reset,
+		.read_u64 = mem_cgroup_read_u64,
+	},
+	{ },	/* terminate */
+};
+
+static int __init mem_cgroup_swap_init(void)
+{
+	if (!mem_cgroup_disabled() && really_do_swap_account) {
+		do_swap_account = 1;
+		WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys,
+						  memsw_cgroup_files));
+	}
+	return 0;
+}
+subsys_initcall(mem_cgroup_swap_init);
+
+#endif /* CONFIG_MEMCG_SWAP */