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 <[email protected]>
---
Changelog:
v1->v2:
  None
v2->v3:
  None
v3->v4:
  - Implement high priority workqueue independently.
    Now high priority wq is implemented as a normal btrfs_workqueue,
    with independent ordering/thresholding mechanism.
    This fixed the problem that high priority wq and normal wq shared one
    ordered wq.
---
 fs/btrfs/async-thread.c | 89 +++++++++++++++++++++++++++++++++++++++++++------
 fs/btrfs/async-thread.h |  5 ++-
 2 files changed, 82 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index f05d57e..73b9f94 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -729,7 +729,7 @@ 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;
@@ -738,6 +738,38 @@ 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)
@@ -747,19 +779,25 @@ 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;
@@ -832,8 +870,8 @@ 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;
 
@@ -846,13 +884,42 @@ 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 1d16156..62cd19d 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
-- 
1.8.5.1

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