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-rw-r--r--fs/btrfs/async-thread.c81
1 files changed, 73 insertions, 8 deletions
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 282ca085c2fb..c0861e781cdb 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -64,6 +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.
*/
@@ -118,11 +163,13 @@ static void check_pending_worker_creates(struct btrfs_worker_thread *worker)
goto out;
workers->atomic_start_pending = 0;
- if (workers->num_workers >= workers->max_workers)
+ if (workers->num_workers + workers->num_workers_starting >=
+ workers->max_workers)
goto out;
+ workers->num_workers_starting += 1;
spin_unlock_irqrestore(&workers->lock, flags);
- btrfs_start_workers(workers, 1);
+ start_new_worker(workers);
return;
out:
@@ -390,9 +437,11 @@ int btrfs_stop_workers(struct btrfs_workers *workers)
/*
* 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);
@@ -404,14 +453,15 @@ void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max)
workers->name = name;
workers->ordered = 0;
workers->atomic_start_pending = 0;
- workers->atomic_worker_start = 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;
@@ -444,6 +494,8 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers)
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;
@@ -452,6 +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
@@ -461,7 +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
@@ -509,15 +572,17 @@ again:
worker = next_worker(workers);
if (!worker) {
- if (workers->num_workers >= workers->max_workers) {
+ 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;
}
}