[PATCH] __try_module_get()

[Rusty Russell]

Linus, please apply.

Name: __try_module_get
Author: Rusty Russell
Status: Trivial

D: Introduces __try_module_get for places where we know we already hold
D: a reference and ignoring the fact that the module is being "rmmod --wait"ed
D: is simpler.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .5936-linux-2.5.66-bk2/fs/filesystems.c .5936-linux-2.5.66-bk2.updated/fs/filesystems.c
--- .5936-linux-2.5.66-bk2/fs/filesystems.c	2003-03-18 12:21:38.000000000 +1100
+++ .5936-linux-2.5.66-bk2.updated/fs/filesystems.c	2003-03-27 12:58:34.000000000 +1100
@@ -32,17 +32,7 @@ static rwlock_t file_systems_lock = RW_L
 /* WARNING: This can be used only if we _already_ own a reference */
 void get_filesystem(struct file_system_type *fs)
 {
-	if (!try_module_get(fs->owner)) {
-#ifdef CONFIG_MODULE_UNLOAD
-		unsigned int cpu = get_cpu();
-		local_inc(&fs->owner->ref[cpu].count);
-		put_cpu();
-#else
-		/* Getting filesystem while it's starting up?  We're
-                   already supposed to have a reference. */
-		BUG();
-#endif
-	}
+	__try_module_get(fs->owner);
 }
 
 void put_filesystem(struct file_system_type *fs)
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .5936-linux-2.5.66-bk2/include/linux/module.h .5936-linux-2.5.66-bk2.updated/include/linux/module.h
--- .5936-linux-2.5.66-bk2/include/linux/module.h	2003-03-25 12:17:31.000000000 +1100
+++ .5936-linux-2.5.66-bk2.updated/include/linux/module.h	2003-03-27 12:58:34.000000000 +1100
@@ -272,6 +272,7 @@ int module_text_address(unsigned long ad
 
 #ifdef CONFIG_MODULE_UNLOAD
 
+unsigned int module_refcount(struct module *mod);
 void __symbol_put(const char *symbol);
 #define symbol_put(x) __symbol_put(MODULE_SYMBOL_PREFIX #x)
 void symbol_put_addr(void *addr);
@@ -282,6 +283,17 @@ void symbol_put_addr(void *addr);
 #define local_dec(x) atomic_dec(x)
 #endif
 
+/* Sometimes we know we already have a refcount, and it's easier not
+   to handle the error case (which only happens with rmmod --wait). */
+static inline void __try_module_get(struct module *module)
+{
+	if (module) {
+		BUG_ON(module_refcount(module) == 0);
+		local_inc(&module->ref[get_cpu()].count);
+		put_cpu();
+	}
+}
+
 static inline int try_module_get(struct module *module)
 {
 	int ret = 1;
@@ -317,6 +329,9 @@ static inline int try_module_get(struct 
 static inline void module_put(struct module *module)
 {
 }
+static inline void __try_module_get(struct module *module)
+{
+}
 #define symbol_put(x) do { } while(0)
 #define symbol_put_addr(p) do { } while(0)
 
@@ -371,6 +386,10 @@ static inline int module_text_address(un
 #define symbol_put(x) do { } while(0)
 #define symbol_put_addr(x) do { } while(0)
 
+static inline void __try_module_get(struct module *module)
+{
+}
+
 static inline int try_module_get(struct module *module)
 {
 	return 1;
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .5936-linux-2.5.66-bk2/kernel/module.c .5936-linux-2.5.66-bk2.updated/kernel/module.c
--- .5936-linux-2.5.66-bk2/kernel/module.c	2003-03-18 05:01:52.000000000 +1100
+++ .5936-linux-2.5.66-bk2.updated/kernel/module.c	2003-03-27 12:59:06.000000000 +1100
@@ -374,7 +374,7 @@ static inline void restart_refcounts(voi
 }
 #endif
 
-static unsigned int module_refcount(struct module *mod)
+unsigned int module_refcount(struct module *mod)
 {
 	unsigned int i, total = 0;
 
@@ -382,6 +382,7 @@ static unsigned int module_refcount(stru
 		total += atomic_read(&mod->ref[i].count);
 	return total;
 }
+EXPORT_SYMBOL(module_refcount);
 
 /* This exists whether we can unload or not */
 static void free_module(struct module *mod);

--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.