btrfs: Add high priority workqueue support for btrfs_workqueue_struct

Add high priority function to btrfs_workqueue.

This is implemented by embedding a btrfs_workqueue into a
btrfs_workqueue and use some helper functions to differ the normal
priority wq and high priority wq.
So the high priority wq is completely independent from the normal
workqueue.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Tested-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>

2 files changed, 83 insertions, 13 deletions

diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 905de02e4386..193c84964db9 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -730,7 +730,7 @@ void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work)
         spin_unlock_irqrestore(&worker->lock, flags);
 }
 
-struct btrfs_workqueue_struct {
+struct __btrfs_workqueue_struct {
         struct workqueue_struct *normal_wq;
         /* List head pointing to ordered work list */
         struct list_head ordered_list;
@@ -739,6 +739,38 @@ struct btrfs_workqueue_struct {
         spinlock_t list_lock;
 };
 
+struct btrfs_workqueue_struct {
+        struct __btrfs_workqueue_struct *normal;
+        struct __btrfs_workqueue_struct *high;
+};
+
+static inline struct __btrfs_workqueue_struct
+*__btrfs_alloc_workqueue(char *name, int flags, int max_active)
+{
+        struct __btrfs_workqueue_struct *ret = kzalloc(sizeof(*ret), GFP_NOFS);
+
+        if (unlikely(!ret))
+                return NULL;
+
+        if (flags & WQ_HIGHPRI)
+                ret->normal_wq = alloc_workqueue("%s-%s-high", flags,
+                                                 max_active, "btrfs", name);
+        else
+                ret->normal_wq = alloc_workqueue("%s-%s", flags,
+                                                 max_active, "btrfs", name);
+        if (unlikely(!ret->normal_wq)) {
+                kfree(ret);
+                return NULL;
+        }
+
+        INIT_LIST_HEAD(&ret->ordered_list);
+        spin_lock_init(&ret->list_lock);
+        return ret;
+}
+
+static inline void
+__btrfs_destroy_workqueue(struct __btrfs_workqueue_struct *wq);
+
 struct btrfs_workqueue_struct *btrfs_alloc_workqueue(char *name,
                                                      int flags,
                                                      int max_active)
@@ -748,19 +780,25 @@ struct btrfs_workqueue_struct *btrfs_alloc_workqueue(char *name,
         if (unlikely(!ret))
                 return NULL;
 
-        ret->normal_wq = alloc_workqueue("%s-%s", flags, max_active,
-                                         "btrfs", name);
-        if (unlikely(!ret->normal_wq)) {
+        ret->normal = __btrfs_alloc_workqueue(name, flags & ~WQ_HIGHPRI,
+                                              max_active);
+        if (unlikely(!ret->normal)) {
                 kfree(ret);
                 return NULL;
         }
 
-        INIT_LIST_HEAD(&ret->ordered_list);
-        spin_lock_init(&ret->list_lock);
+        if (flags & WQ_HIGHPRI) {
+                ret->high = __btrfs_alloc_workqueue(name, flags, max_active);
+                if (unlikely(!ret->high)) {
+                        __btrfs_destroy_workqueue(ret->normal);
+                        kfree(ret);
+                        return NULL;
+                }
+        }
         return ret;
 }
 
-static void run_ordered_work(struct btrfs_workqueue_struct *wq)
+static void run_ordered_work(struct __btrfs_workqueue_struct *wq)
 {
         struct list_head *list = &wq->ordered_list;
         struct btrfs_work_struct *work;
@@ -804,7 +842,7 @@ static void run_ordered_work(struct btrfs_workqueue_struct *wq)
 static void normal_work_helper(struct work_struct *arg)
 {
         struct btrfs_work_struct *work;
-        struct btrfs_workqueue_struct *wq;
+        struct __btrfs_workqueue_struct *wq;
         int need_order = 0;
 
         work = container_of(arg, struct btrfs_work_struct, normal_work);
@@ -840,8 +878,8 @@ void btrfs_init_work(struct btrfs_work_struct *work,
         work->flags = 0;
 }
 
-void btrfs_queue_work(struct btrfs_workqueue_struct *wq,
-                      struct btrfs_work_struct *work)
+static inline void __btrfs_queue_work(struct __btrfs_workqueue_struct *wq,
+                                      struct btrfs_work_struct *work)
 {
         unsigned long flags;
 
@@ -854,13 +892,42 @@ void btrfs_queue_work(struct btrfs_workqueue_struct *wq,
         queue_work(wq->normal_wq, &work->normal_work);
 }
 
-void btrfs_destroy_workqueue(struct btrfs_workqueue_struct *wq)
+void btrfs_queue_work(struct btrfs_workqueue_struct *wq,
+                      struct btrfs_work_struct *work)
+{
+        struct __btrfs_workqueue_struct *dest_wq;
+
+        if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags) && wq->high)
+                dest_wq = wq->high;
+        else
+                dest_wq = wq->normal;
+        __btrfs_queue_work(dest_wq, work);
+}
+
+static inline void
+__btrfs_destroy_workqueue(struct __btrfs_workqueue_struct *wq)
 {
         destroy_workqueue(wq->normal_wq);
         kfree(wq);
 }
 
+void btrfs_destroy_workqueue(struct btrfs_workqueue_struct *wq)
+{
+        if (!wq)
+                return;
+        if (wq->high)
+                __btrfs_destroy_workqueue(wq->high);
+        __btrfs_destroy_workqueue(wq->normal);
+}
+
 void btrfs_workqueue_set_max(struct btrfs_workqueue_struct *wq, int max)
 {
-        workqueue_set_max_active(wq->normal_wq, max);
+        workqueue_set_max_active(wq->normal->normal_wq, max);
+        if (wq->high)
+                workqueue_set_max_active(wq->high->normal_wq, max);
+}
+
+void btrfs_set_work_high_priority(struct btrfs_work_struct *work)
+{
+        set_bit(WORK_HIGH_PRIO_BIT, &work->flags);
 }
diff --git a/fs/btrfs/async-thread.h b/fs/btrfs/async-thread.h
index 9d8da53f6dd9..fce623cfe3da 100644
--- a/fs/btrfs/async-thread.h
+++ b/fs/btrfs/async-thread.h
@@ -121,6 +121,8 @@ void btrfs_requeue_work(struct btrfs_work *work);
 void btrfs_set_work_high_prio(struct btrfs_work *work);
 
 struct btrfs_workqueue_struct;
+/* Internal use only */
+struct __btrfs_workqueue_struct;
 
 struct btrfs_work_struct {
         void (*func)(struct btrfs_work_struct *arg);
@@ -130,7 +132,7 @@ struct btrfs_work_struct {
         /* Don't touch things below */
         struct work_struct normal_work;
         struct list_head ordered_list;
-        struct btrfs_workqueue_struct *wq;
+        struct __btrfs_workqueue_struct *wq;
         unsigned long flags;
 };
 
@@ -145,4 +147,5 @@ void btrfs_queue_work(struct btrfs_workqueue_struct *wq,
                       struct btrfs_work_struct *work);
 void btrfs_destroy_workqueue(struct btrfs_workqueue_struct *wq);
 void btrfs_workqueue_set_max(struct btrfs_workqueue_struct *wq, int max);
+void btrfs_set_work_high_priority(struct btrfs_work_struct *work);
 #endif