module: Rework module_addr_{min,max}

__module_address() does an initial bound check before doing the
{list/tree} iteration to find the actual module. The bound variables
are nowhere near the mod_tree cacheline, in fact they're nowhere near
one another.

module_addr_min lives in .data while module_addr_max lives in .bss
(smarty pants GCC thinks the explicit 0 assignment is a mistake).

Rectify this by moving the two variables into a structure together
with the latch_tree_root to guarantee they all share the same
cacheline and avoid hitting two extra cachelines for the lookup.

While reworking the bounds code, move the bound update from allocation
to insertion time, this avoids updating the bounds for a few error
paths.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

kernel/module.c

@@ -170,7 +170,26 @@ static const struct latch_tree_ops mod_tree_ops = {
 	.comp = mod_tree_comp,
 };
 
-static struct latch_tree_root mod_tree __cacheline_aligned;
+static struct mod_tree_root {
+	struct latch_tree_root root;
+	unsigned long addr_min;
+	unsigned long addr_max;
+} mod_tree __cacheline_aligned = {
+	.addr_min = -1UL,
+};
+
+#define module_addr_min mod_tree.addr_min
+#define module_addr_max mod_tree.addr_max
+
+static noinline void __mod_tree_insert(struct mod_tree_node *node)
+{
+	latch_tree_insert(&node->node, &mod_tree.root, &mod_tree_ops);
+}
+
+static void __mod_tree_remove(struct mod_tree_node *node)
+{
+	latch_tree_erase(&node->node, &mod_tree.root, &mod_tree_ops);
+}
 
 /*
  * These modifications: insert, remove_init and remove; are serialized by the
@@ -181,20 +200,20 @@ static void mod_tree_insert(struct module *mod)
 	mod->mtn_core.mod = mod;
 	mod->mtn_init.mod = mod;
 
-	latch_tree_insert(&mod->mtn_core.node, &mod_tree, &mod_tree_ops);
+	__mod_tree_insert(&mod->mtn_core);
 	if (mod->init_size)
-		latch_tree_insert(&mod->mtn_init.node, &mod_tree, &mod_tree_ops);
+		__mod_tree_insert(&mod->mtn_init);
 }
 
 static void mod_tree_remove_init(struct module *mod)
 {
 	if (mod->init_size)
-		latch_tree_erase(&mod->mtn_init.node, &mod_tree, &mod_tree_ops);
+		__mod_tree_remove(&mod->mtn_init);
 }
 
 static void mod_tree_remove(struct module *mod)
 {
-	latch_tree_erase(&mod->mtn_core.node, &mod_tree, &mod_tree_ops);
+	__mod_tree_remove(&mod->mtn_core);
 	mod_tree_remove_init(mod);
 }
 
@@ -202,7 +221,7 @@ static struct module *mod_find(unsigned long addr)
 {
 	struct latch_tree_node *ltn;
 
-	ltn = latch_tree_find((void *)addr, &mod_tree, &mod_tree_ops);
+	ltn = latch_tree_find((void *)addr, &mod_tree.root, &mod_tree_ops);
 	if (!ltn)
 		return NULL;
 
@@ -211,6 +230,8 @@ static struct module *mod_find(unsigned long addr)
 
 #else /* MODULES_TREE_LOOKUP */
 
+static unsigned long module_addr_min = -1UL, module_addr_max = 0;
+
 static void mod_tree_insert(struct module *mod) { }
 static void mod_tree_remove_init(struct module *mod) { }
 static void mod_tree_remove(struct module *mod) { }
@@ -229,6 +250,28 @@ static struct module *mod_find(unsigned long addr)
 
 #endif /* MODULES_TREE_LOOKUP */
 
+/*
+ * Bounds of module text, for speeding up __module_address.
+ * Protected by module_mutex.
+ */
+static void __mod_update_bounds(void *base, unsigned int size)
+{
+	unsigned long min = (unsigned long)base;
+	unsigned long max = min + size;
+
+	if (min < module_addr_min)
+		module_addr_min = min;
+	if (max > module_addr_max)
+		module_addr_max = max;
+}
+
+static void mod_update_bounds(struct module *mod)
+{
+	__mod_update_bounds(mod->module_core, mod->core_size);
+	if (mod->init_size)
+		__mod_update_bounds(mod->module_init, mod->init_size);
+}
+
 #ifdef CONFIG_KGDB_KDB
 struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */
 #endif /* CONFIG_KGDB_KDB */
@@ -297,10 +340,6 @@ static DECLARE_WAIT_QUEUE_HEAD(module_wq);
 
 static BLOCKING_NOTIFIER_HEAD(module_notify_list);
 
-/* Bounds of module allocation, for speeding __module_address.
- * Protected by module_mutex. */
-static unsigned long module_addr_min = -1UL, module_addr_max = 0;
-
 int register_module_notifier(struct notifier_block *nb)
 {
 	return blocking_notifier_chain_register(&module_notify_list, nb);
@@ -2539,22 +2578,6 @@ void * __weak module_alloc(unsigned long size)
 	return vmalloc_exec(size);
 }
 
-static void *module_alloc_update_bounds(unsigned long size)
-{
-	void *ret = module_alloc(size);
-
-	if (ret) {
-		mutex_lock(&module_mutex);
-		/* Update module bounds. */
-		if ((unsigned long)ret < module_addr_min)
-			module_addr_min = (unsigned long)ret;
-		if ((unsigned long)ret + size > module_addr_max)
-			module_addr_max = (unsigned long)ret + size;
-		mutex_unlock(&module_mutex);
-	}
-	return ret;
-}
-
 #ifdef CONFIG_DEBUG_KMEMLEAK
 static void kmemleak_load_module(const struct module *mod,
 				 const struct load_info *info)
@@ -2960,7 +2983,7 @@ static int move_module(struct module *mod, struct load_info *info)
 	void *ptr;
 
 	/* Do the allocs. */
-	ptr = module_alloc_update_bounds(mod->core_size);
+	ptr = module_alloc(mod->core_size);
 	/*
 	 * The pointer to this block is stored in the module structure
 	 * which is inside the block. Just mark it as not being a
@@ -2974,7 +2997,7 @@ static int move_module(struct module *mod, struct load_info *info)
 	mod->module_core = ptr;
 
 	if (mod->init_size) {
-		ptr = module_alloc_update_bounds(mod->init_size);
+		ptr = module_alloc(mod->init_size);
 		/*
 		 * The pointer to this block is stored in the module structure
 		 * which is inside the block. This block doesn't need to be
@@ -3344,6 +3367,7 @@ again:
 		err = -EEXIST;
 		goto out;
 	}
+	mod_update_bounds(mod);
 	list_add_rcu(&mod->list, &modules);
 	mod_tree_insert(mod);
 	err = 0;