Merge commit 'v2.6.32' into reiserfs/kill-bkl

Merge-reason: The tree was based 2.6.31. It's better to be up to date
with 2.6.32. Although no conflicting changes were made in between,
it gives benchmarking results closer to the lastest kernel behaviour.

1 files changed, 272 insertions, 57 deletions

diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 019e8af449ab..c0861e781cdb 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -48,6 +48,9 @@ struct btrfs_worker_thread {
         /* number of things on the pending list */
         atomic_t num_pending;
 
+        /* reference counter for this struct */
+        atomic_t refs;
+
         unsigned long sequence;
 
         /* protects the pending list. */
@@ -61,6 +64,51 @@ struct btrfs_worker_thread {
 };
 
 /*
+ * btrfs_start_workers uses kthread_run, which can block waiting for memory
+ * for a very long time.  It will actually throttle on page writeback,
+ * and so it may not make progress until after our btrfs worker threads
+ * process all of the pending work structs in their queue
+ *
+ * This means we can't use btrfs_start_workers from inside a btrfs worker
+ * thread that is used as part of cleaning dirty memory, which pretty much
+ * involves all of the worker threads.
+ *
+ * Instead we have a helper queue who never has more than one thread
+ * where we scheduler thread start operations.  This worker_start struct
+ * is used to contain the work and hold a pointer to the queue that needs
+ * another worker.
+ */
+struct worker_start {
+        struct btrfs_work work;
+        struct btrfs_workers *queue;
+};
+
+static void start_new_worker_func(struct btrfs_work *work)
+{
+        struct worker_start *start;
+        start = container_of(work, struct worker_start, work);
+        btrfs_start_workers(start->queue, 1);
+        kfree(start);
+}
+
+static int start_new_worker(struct btrfs_workers *queue)
+{
+        struct worker_start *start;
+        int ret;
+
+        start = kzalloc(sizeof(*start), GFP_NOFS);
+        if (!start)
+                return -ENOMEM;
+
+        start->work.func = start_new_worker_func;
+        start->queue = queue;
+        ret = btrfs_queue_worker(queue->atomic_worker_start, &start->work);
+        if (ret)
+                kfree(start);
+        return ret;
+}
+
+/*
  * helper function to move a thread onto the idle list after it
  * has finished some requests.
  */
@@ -71,7 +119,12 @@ static void check_idle_worker(struct btrfs_worker_thread *worker)
                 unsigned long flags;
                 spin_lock_irqsave(&worker->workers->lock, flags);
                 worker->idle = 1;
-                list_move(&worker->worker_list, &worker->workers->idle_list);
+
+                /* the list may be empty if the worker is just starting */
+                if (!list_empty(&worker->worker_list)) {
+                        list_move(&worker->worker_list,
+                                 &worker->workers->idle_list);
+                }
                 spin_unlock_irqrestore(&worker->workers->lock, flags);
         }
 }
@@ -87,23 +140,51 @@ static void check_busy_worker(struct btrfs_worker_thread *worker)
                 unsigned long flags;
                 spin_lock_irqsave(&worker->workers->lock, flags);
                 worker->idle = 0;
-                list_move_tail(&worker->worker_list,
-                               &worker->workers->worker_list);
+
+                if (!list_empty(&worker->worker_list)) {
+                        list_move_tail(&worker->worker_list,
+                                      &worker->workers->worker_list);
+                }
                 spin_unlock_irqrestore(&worker->workers->lock, flags);
         }
 }
 
-static noinline int run_ordered_completions(struct btrfs_workers *workers,
-                                            struct btrfs_work *work)
+static void check_pending_worker_creates(struct btrfs_worker_thread *worker)
 {
+        struct btrfs_workers *workers = worker->workers;
         unsigned long flags;
 
+        rmb();
+        if (!workers->atomic_start_pending)
+                return;
+
+        spin_lock_irqsave(&workers->lock, flags);
+        if (!workers->atomic_start_pending)
+                goto out;
+
+        workers->atomic_start_pending = 0;
+        if (workers->num_workers + workers->num_workers_starting >=
+            workers->max_workers)
+                goto out;
+
+        workers->num_workers_starting += 1;
+        spin_unlock_irqrestore(&workers->lock, flags);
+        start_new_worker(workers);
+        return;
+
+out:
+        spin_unlock_irqrestore(&workers->lock, flags);
+}
+
+static noinline int run_ordered_completions(struct btrfs_workers *workers,
+                                            struct btrfs_work *work)
+{
         if (!workers->ordered)
                 return 0;
 
         set_bit(WORK_DONE_BIT, &work->flags);
 
-        spin_lock_irqsave(&workers->lock, flags);
+        spin_lock(&workers->order_lock);
 
         while (1) {
                 if (!list_empty(&workers->prio_order_list)) {
@@ -126,45 +207,118 @@ static noinline int run_ordered_completions(struct btrfs_workers *workers,
                 if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags))
                         break;
 
-                spin_unlock_irqrestore(&workers->lock, flags);
+                spin_unlock(&workers->order_lock);
 
                 work->ordered_func(work);
 
                 /* now take the lock again and call the freeing code */
-                spin_lock_irqsave(&workers->lock, flags);
+                spin_lock(&workers->order_lock);
                 list_del(&work->order_list);
                 work->ordered_free(work);
         }
 
-        spin_unlock_irqrestore(&workers->lock, flags);
+        spin_unlock(&workers->order_lock);
         return 0;
 }
 
+static void put_worker(struct btrfs_worker_thread *worker)
+{
+        if (atomic_dec_and_test(&worker->refs))
+                kfree(worker);
+}
+
+static int try_worker_shutdown(struct btrfs_worker_thread *worker)
+{
+        int freeit = 0;
+
+        spin_lock_irq(&worker->lock);
+        spin_lock(&worker->workers->lock);
+        if (worker->workers->num_workers > 1 &&
+            worker->idle &&
+            !worker->working &&
+            !list_empty(&worker->worker_list) &&
+            list_empty(&worker->prio_pending) &&
+            list_empty(&worker->pending) &&
+            atomic_read(&worker->num_pending) == 0) {
+                freeit = 1;
+                list_del_init(&worker->worker_list);
+                worker->workers->num_workers--;
+        }
+        spin_unlock(&worker->workers->lock);
+        spin_unlock_irq(&worker->lock);
+
+        if (freeit)
+                put_worker(worker);
+        return freeit;
+}
+
+static struct btrfs_work *get_next_work(struct btrfs_worker_thread *worker,
+                                        struct list_head *prio_head,
+                                        struct list_head *head)
+{
+        struct btrfs_work *work = NULL;
+        struct list_head *cur = NULL;
+
+        if(!list_empty(prio_head))
+                cur = prio_head->next;
+
+        smp_mb();
+        if (!list_empty(&worker->prio_pending))
+                goto refill;
+
+        if (!list_empty(head))
+                cur = head->next;
+
+        if (cur)
+                goto out;
+
+refill:
+        spin_lock_irq(&worker->lock);
+        list_splice_tail_init(&worker->prio_pending, prio_head);
+        list_splice_tail_init(&worker->pending, head);
+
+        if (!list_empty(prio_head))
+                cur = prio_head->next;
+        else if (!list_empty(head))
+                cur = head->next;
+        spin_unlock_irq(&worker->lock);
+
+        if (!cur)
+                goto out_fail;
+
+out:
+        work = list_entry(cur, struct btrfs_work, list);
+
+out_fail:
+        return work;
+}
+
 /*
  * main loop for servicing work items
  */
 static int worker_loop(void *arg)
 {
         struct btrfs_worker_thread *worker = arg;
-        struct list_head *cur;
+        struct list_head head;
+        struct list_head prio_head;
         struct btrfs_work *work;
+
+        INIT_LIST_HEAD(&head);
+        INIT_LIST_HEAD(&prio_head);
+
         do {
-                spin_lock_irq(&worker->lock);
-again_locked:
+again:
                 while (1) {
-                        if (!list_empty(&worker->prio_pending))
-                                cur = worker->prio_pending.next;
-                        else if (!list_empty(&worker->pending))
-                                cur = worker->pending.next;
-                        else
+
+
+                        work = get_next_work(worker, &prio_head, &head);
+                        if (!work)
                                 break;
 
-                        work = list_entry(cur, struct btrfs_work, list);
                         list_del(&work->list);
                         clear_bit(WORK_QUEUED_BIT, &work->flags);
 
                         work->worker = worker;
-                        spin_unlock_irq(&worker->lock);
 
                         work->func(work);
 
@@ -175,9 +329,13 @@ again_locked:
                          */
                         run_ordered_completions(worker->workers, work);
 
-                        spin_lock_irq(&worker->lock);
-                        check_idle_worker(worker);
+                        check_pending_worker_creates(worker);
+
                 }
+
+                spin_lock_irq(&worker->lock);
+                check_idle_worker(worker);
+
                 if (freezing(current)) {
                         worker->working = 0;
                         spin_unlock_irq(&worker->lock);
@@ -216,8 +374,10 @@ again_locked:
                                 spin_lock_irq(&worker->lock);
                                 set_current_state(TASK_INTERRUPTIBLE);
                                 if (!list_empty(&worker->pending) ||
-                                    !list_empty(&worker->prio_pending))
-                                        goto again_locked;
+                                    !list_empty(&worker->prio_pending)) {
+                                        spin_unlock_irq(&worker->lock);
+                                        goto again;
+                                }
 
                                 /*
                                  * this makes sure we get a wakeup when someone
@@ -226,8 +386,13 @@ again_locked:
                                 worker->working = 0;
                                 spin_unlock_irq(&worker->lock);
 
-                                if (!kthread_should_stop())
-                                        schedule();
+                                if (!kthread_should_stop()) {
+                                        schedule_timeout(HZ * 120);
+                                        if (!worker->working &&
+                                            try_worker_shutdown(worker)) {
+                                                return 0;
+                                        }
+                                }
                         }
                         __set_current_state(TASK_RUNNING);
                 }
@@ -242,41 +407,61 @@ int btrfs_stop_workers(struct btrfs_workers *workers)
 {
         struct list_head *cur;
         struct btrfs_worker_thread *worker;
+        int can_stop;
 
+        spin_lock_irq(&workers->lock);
         list_splice_init(&workers->idle_list, &workers->worker_list);
         while (!list_empty(&workers->worker_list)) {
                 cur = workers->worker_list.next;
                 worker = list_entry(cur, struct btrfs_worker_thread,
                                     worker_list);
-                kthread_stop(worker->task);
-                list_del(&worker->worker_list);
-                kfree(worker);
+
+                atomic_inc(&worker->refs);
+                workers->num_workers -= 1;
+                if (!list_empty(&worker->worker_list)) {
+                        list_del_init(&worker->worker_list);
+                        put_worker(worker);
+                        can_stop = 1;
+                } else
+                        can_stop = 0;
+                spin_unlock_irq(&workers->lock);
+                if (can_stop)
+                        kthread_stop(worker->task);
+                spin_lock_irq(&workers->lock);
+                put_worker(worker);
         }
+        spin_unlock_irq(&workers->lock);
         return 0;
 }
 
 /*
  * simple init on struct btrfs_workers
  */
-void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max)
+void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max,
+                        struct btrfs_workers *async_helper)
 {
         workers->num_workers = 0;
+        workers->num_workers_starting = 0;
         INIT_LIST_HEAD(&workers->worker_list);
         INIT_LIST_HEAD(&workers->idle_list);
         INIT_LIST_HEAD(&workers->order_list);
         INIT_LIST_HEAD(&workers->prio_order_list);
         spin_lock_init(&workers->lock);
+        spin_lock_init(&workers->order_lock);
         workers->max_workers = max;
         workers->idle_thresh = 32;
         workers->name = name;
         workers->ordered = 0;
+        workers->atomic_start_pending = 0;
+        workers->atomic_worker_start = async_helper;
 }
 
 /*
  * starts new worker threads.  This does not enforce the max worker
  * count in case you need to temporarily go past it.
  */
-int btrfs_start_workers(struct btrfs_workers *workers, int num_workers)
+static int __btrfs_start_workers(struct btrfs_workers *workers,
+                                 int num_workers)
 {
         struct btrfs_worker_thread *worker;
         int ret = 0;
@@ -293,7 +478,9 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers)
                 INIT_LIST_HEAD(&worker->prio_pending);
                 INIT_LIST_HEAD(&worker->worker_list);
                 spin_lock_init(&worker->lock);
+
                 atomic_set(&worker->num_pending, 0);
+                atomic_set(&worker->refs, 1);
                 worker->workers = workers;
                 worker->task = kthread_run(worker_loop, worker,
                                            "btrfs-%s-%d", workers->name,
@@ -303,11 +490,12 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers)
                         kfree(worker);
                         goto fail;
                 }
-
                 spin_lock_irq(&workers->lock);
                 list_add_tail(&worker->worker_list, &workers->idle_list);
                 worker->idle = 1;
                 workers->num_workers++;
+                workers->num_workers_starting--;
+                WARN_ON(workers->num_workers_starting < 0);
                 spin_unlock_irq(&workers->lock);
         }
         return 0;
@@ -316,6 +504,14 @@ fail:
         return ret;
 }
 
+int btrfs_start_workers(struct btrfs_workers *workers, int num_workers)
+{
+        spin_lock_irq(&workers->lock);
+        workers->num_workers_starting += num_workers;
+        spin_unlock_irq(&workers->lock);
+        return __btrfs_start_workers(workers, num_workers);
+}
+
 /*
  * run through the list and find a worker thread that doesn't have a lot
  * to do right now.  This can return null if we aren't yet at the thread
@@ -325,7 +521,10 @@ static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers)
 {
         struct btrfs_worker_thread *worker;
         struct list_head *next;
-        int enforce_min = workers->num_workers < workers->max_workers;
+        int enforce_min;
+
+        enforce_min = (workers->num_workers + workers->num_workers_starting) <
+                workers->max_workers;
 
         /*
          * if we find an idle thread, don't move it to the end of the
@@ -350,7 +549,6 @@ static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers)
          */
         next = workers->worker_list.next;
         worker = list_entry(next, struct btrfs_worker_thread, worker_list);
-        atomic_inc(&worker->num_pending);
         worker->sequence++;
 
         if (worker->sequence % workers->idle_thresh == 0)
@@ -367,35 +565,49 @@ static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers)
 {
         struct btrfs_worker_thread *worker;
         unsigned long flags;
+        struct list_head *fallback;
 
 again:
         spin_lock_irqsave(&workers->lock, flags);
         worker = next_worker(workers);
-        spin_unlock_irqrestore(&workers->lock, flags);
 
         if (!worker) {
-                spin_lock_irqsave(&workers->lock, flags);
-                if (workers->num_workers >= workers->max_workers) {
-                        struct list_head *fallback = NULL;
-                        /*
-                         * we have failed to find any workers, just
-                         * return the force one
-                         */
-                        if (!list_empty(&workers->worker_list))
-                                fallback = workers->worker_list.next;
-                        if (!list_empty(&workers->idle_list))
-                                fallback = workers->idle_list.next;
-                        BUG_ON(!fallback);
-                        worker = list_entry(fallback,
-                                  struct btrfs_worker_thread, worker_list);
-                        spin_unlock_irqrestore(&workers->lock, flags);
+                if (workers->num_workers + workers->num_workers_starting >=
+                    workers->max_workers) {
+                        goto fallback;
+                } else if (workers->atomic_worker_start) {
+                        workers->atomic_start_pending = 1;
+                        goto fallback;
                 } else {
+                        workers->num_workers_starting++;
                         spin_unlock_irqrestore(&workers->lock, flags);
                         /* we're below the limit, start another worker */
-                        btrfs_start_workers(workers, 1);
+                        __btrfs_start_workers(workers, 1);
                         goto again;
                 }
         }
+        goto found;
+
+fallback:
+        fallback = NULL;
+        /*
+         * we have failed to find any workers, just
+         * return the first one we can find.
+         */
+        if (!list_empty(&workers->worker_list))
+                fallback = workers->worker_list.next;
+        if (!list_empty(&workers->idle_list))
+                fallback = workers->idle_list.next;
+        BUG_ON(!fallback);
+        worker = list_entry(fallback,
+                  struct btrfs_worker_thread, worker_list);
+found:
+        /*
+         * this makes sure the worker doesn't exit before it is placed
+         * onto a busy/idle list
+         */
+        atomic_inc(&worker->num_pending);
+        spin_unlock_irqrestore(&workers->lock, flags);
         return worker;
 }
 
@@ -427,7 +639,7 @@ int btrfs_requeue_work(struct btrfs_work *work)
                 spin_lock(&worker->workers->lock);
                 worker->idle = 0;
                 list_move_tail(&worker->worker_list,
-                               &worker->workers->worker_list);
+                              &worker->workers->worker_list);
                 spin_unlock(&worker->workers->lock);
         }
         if (!worker->working) {
@@ -435,9 +647,9 @@ int btrfs_requeue_work(struct btrfs_work *work)
                 worker->working = 1;
         }
 
-        spin_unlock_irqrestore(&worker->lock, flags);
         if (wake)
                 wake_up_process(worker->task);
+        spin_unlock_irqrestore(&worker->lock, flags);
 out:
 
         return 0;
@@ -463,14 +675,18 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work)
 
         worker = find_worker(workers);
         if (workers->ordered) {
-                spin_lock_irqsave(&workers->lock, flags);
+                /*
+                 * you're not allowed to do ordered queues from an
+                 * interrupt handler
+                 */
+                spin_lock(&workers->order_lock);
                 if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags)) {
                         list_add_tail(&work->order_list,
                                       &workers->prio_order_list);
                 } else {
                         list_add_tail(&work->order_list, &workers->order_list);
                 }
-                spin_unlock_irqrestore(&workers->lock, flags);
+                spin_unlock(&workers->order_lock);
         } else {
                 INIT_LIST_HEAD(&work->order_list);
         }
@@ -481,7 +697,6 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work)
                 list_add_tail(&work->list, &worker->prio_pending);
         else
                 list_add_tail(&work->list, &worker->pending);
-        atomic_inc(&worker->num_pending);
         check_busy_worker(worker);
 
         /*
@@ -492,10 +707,10 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work)
                 wake = 1;
         worker->working = 1;
 
-        spin_unlock_irqrestore(&worker->lock, flags);
-
         if (wake)
                 wake_up_process(worker->task);
+        spin_unlock_irqrestore(&worker->lock, flags);
+
 out:
         return 0;
 }