Merge branch 'for-3.9-async' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Pull async changes from Tejun Heo:
 "These are followups for the earlier deadlock issue involving async
  ending up waiting for itself through block requesting module[1].  The
  following changes are made by these commits.

   - Instead of requesting default elevator on each request_queue init,
     block now requests it once early during boot.

   - Kmod triggers warning if invoked from an async worker.

   - Async synchronization implementation has been reimplemented.  It's
     a lot simpler now."

* 'for-3.9-async' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  async: initialise list heads to fix crash
  async: replace list of active domains with global list of pending items
  async: keep pending tasks on async_domain and remove async_pending
  async: use ULLONG_MAX for infinity cookie value
  async: bring sanity to the use of words domain and running
  async, kmod: warn on synchronous request_module() from async workers
  block: don't request module during elevator init
  init, block: try to load default elevator module early during boot

9 files changed, 130 insertions, 109 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 9edba1b8323e..603b2c178740 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -100,14 +100,14 @@ static void elevator_put(struct elevator_type *e)
         module_put(e->elevator_owner);
 }
 
-static struct elevator_type *elevator_get(const char *name)
+static struct elevator_type *elevator_get(const char *name, bool try_loading)
 {
         struct elevator_type *e;
 
         spin_lock(&elv_list_lock);
 
         e = elevator_find(name);
-        if (!e) {
+        if (!e && try_loading) {
                 spin_unlock(&elv_list_lock);
                 request_module("%s-iosched", name);
                 spin_lock(&elv_list_lock);
@@ -136,6 +136,22 @@ static int __init elevator_setup(char *str)
 
 __setup("elevator=", elevator_setup);
 
+/* called during boot to load the elevator chosen by the elevator param */
+void __init load_default_elevator_module(void)
+{
+        struct elevator_type *e;
+
+        if (!chosen_elevator[0])
+                return;
+
+        spin_lock(&elv_list_lock);
+        e = elevator_find(chosen_elevator);
+        spin_unlock(&elv_list_lock);
+
+        if (!e)
+                request_module("%s-iosched", chosen_elevator);
+}
+
 static struct kobj_type elv_ktype;
 
 static struct elevator_queue *elevator_alloc(struct request_queue *q,
@@ -191,25 +207,30 @@ int elevator_init(struct request_queue *q, char *name)
         q->boundary_rq = NULL;
 
         if (name) {
-                e = elevator_get(name);
+                e = elevator_get(name, true);
                 if (!e)
                         return -EINVAL;
         }
 
+        /*
+         * Use the default elevator specified by config boot param or
+         * config option.  Don't try to load modules as we could be running
+         * off async and request_module() isn't allowed from async.
+         */
         if (!e && *chosen_elevator) {
-                e = elevator_get(chosen_elevator);
+                e = elevator_get(chosen_elevator, false);
                 if (!e)
                         printk(KERN_ERR "I/O scheduler %s not found\n",
                                                         chosen_elevator);
         }
 
         if (!e) {
-                e = elevator_get(CONFIG_DEFAULT_IOSCHED);
+                e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
                 if (!e) {
                         printk(KERN_ERR
                                 "Default I/O scheduler not found. " \
                                 "Using noop.\n");
-                        e = elevator_get("noop");
+                        e = elevator_get("noop", false);
                 }
         }
 
@@ -951,7 +972,7 @@ int elevator_change(struct request_queue *q, const char *name)
                 return -ENXIO;
 
         strlcpy(elevator_name, name, sizeof(elevator_name));
-        e = elevator_get(strstrip(elevator_name));
+        e = elevator_get(strstrip(elevator_name), true);
         if (!e) {
                 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
                 return -EINVAL;
diff --git a/include/linux/async.h b/include/linux/async.h
index 345169cfa304..a2e3f18b2ad6 100644
--- a/include/linux/async.h
+++ b/include/linux/async.h
@@ -19,8 +19,7 @@ typedef u64 async_cookie_t;
 typedef void (async_func_ptr) (void *data, async_cookie_t cookie);
 struct async_domain {
         struct list_head node;
-        struct list_head domain;
-        int count;
+        struct list_head pending;
         unsigned registered:1;
 };
 
@@ -29,8 +28,7 @@ struct async_domain {
  */
 #define ASYNC_DOMAIN(_name) \
         struct async_domain _name = { .node = LIST_HEAD_INIT(_name.node), \
-                                      .domain = LIST_HEAD_INIT(_name.domain), \
-                                      .count = 0, \
+                                      .pending = LIST_HEAD_INIT(_name.pending), \
                                       .registered = 1 }
 
 /*
@@ -39,8 +37,7 @@ struct async_domain {
  */
 #define ASYNC_DOMAIN_EXCLUSIVE(_name) \
         struct async_domain _name = { .node = LIST_HEAD_INIT(_name.node), \
-                                      .domain = LIST_HEAD_INIT(_name.domain), \
-                                      .count = 0, \
+                                      .pending = LIST_HEAD_INIT(_name.pending), \
                                       .registered = 0 }
 
 extern async_cookie_t async_schedule(async_func_ptr *ptr, void *data);
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index c03af7687bb4..186620631750 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -138,6 +138,7 @@ extern void elv_drain_elevator(struct request_queue *);
 /*
  * io scheduler registration
  */
+extern void __init load_default_elevator_module(void);
 extern int elv_register(struct elevator_type *);
 extern void elv_unregister(struct elevator_type *);
 
@@ -206,5 +207,9 @@ enum {
         INIT_LIST_HEAD(&(rq)->csd.list);        \
         } while (0)
 
+#else /* CONFIG_BLOCK */
+
+static inline void load_default_elevator_module(void) { }
+
 #endif /* CONFIG_BLOCK */
 #endif
diff --git a/include/linux/init.h b/include/linux/init.h
index 10ed4f436458..861814710d52 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -153,6 +153,7 @@ extern unsigned int reset_devices;
 /* used by init/main.c */
 void setup_arch(char **);
 void prepare_namespace(void);
+void __init load_default_modules(void);
 
 extern void (*late_time_init)(void);
 
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index f9acf71b9810..a32ec1ce882b 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -61,6 +61,9 @@ static void __init handle_initrd(void)
         sys_mkdir("/old", 0700);
         sys_chdir("/old");