1 files changed, 78 insertions, 0 deletions

diff --git a/fs/btrfs/async-thread.h b/fs/btrfs/async-thread.h
new file mode 100644
index 000000000000..52fc9da0f9e7
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+++ b/fs/btrfs/async-thread.h
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+/*
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef __BTRFS_ASYNC_THREAD_
+#define __BTRFS_ASYNC_THREAD_
+
+struct btrfs_worker_thread;
+
+/*
+ * This is similar to a workqueue, but it is meant to spread the operations
+ * across all available cpus instead of just the CPU that was used to
+ * queue the work.  There is also some batching introduced to try and
+ * cut down on context switches.
+ *
+ * By default threads are added on demand up to 2 * the number of cpus.
+ * Changing struct btrfs_workers->max_workers is one way to prevent
+ * demand creation of kthreads.
+ *
+ * the basic model of these worker threads is to embed a btrfs_work
+ * structure in your own data struct, and use container_of in a
+ * work function to get back to your data struct.
+ */
+struct btrfs_work {
+        /*
+         * only func should be set to the function you want called
+         * your work struct is passed as the only arg
+         */
+        void (*func)(struct btrfs_work *work);
+
+        /*
+         * flags should be set to zero.  It is used to make sure the
+         * struct is only inserted once into the list.
+         */
+        unsigned long flags;
+
+        /* don't touch these */
+        struct btrfs_worker_thread *worker;
+        struct list_head list;
+};
+
+struct btrfs_workers {
+        /* current number of running workers */
+        int num_workers;
+
+        /* max number of workers allowed.  changed by btrfs_start_workers */
+        int max_workers;
+
+        /* list with all the work threads */
+        struct list_head worker_list;
+
+        /* the last worker thread to have something queued */
+        struct btrfs_worker_thread *last;
+
+        /* lock for finding the next worker thread to queue on */
+        spinlock_t lock;
+};
+
+int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work);
+int btrfs_start_workers(struct btrfs_workers *workers, int num_workers);
+int btrfs_stop_workers(struct btrfs_workers *workers);
+void btrfs_init_workers(struct btrfs_workers *workers, int max);
+int btrfs_requeue_work(struct btrfs_work *work);
+#endif