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

1 files changed, 28 insertions, 7 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;