[PATCH 2/3] block: convert wbt_wait() to use rq_qos_wait()

[Josef Bacik]

Now that we have rq_qos_wait() in place, convert wbt_wait() over to
using it with it's specific callbacks.

Signed-off-by: Josef Bacik <jo...@toxicpanda.com>
---
 block/blk-wbt.c | 65 ++++++++++-----------------------------------------------
 1 file changed, 11 insertions(+), 54 deletions(-)

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index d051ebfb4852..40207edd1d89 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -489,31 +489,21 @@ static inline unsigned int get_limit(struct rq_wb *rwb, 
unsigned long rw)
 }
 
 struct wbt_wait_data {
-       struct wait_queue_entry wq;
-       struct task_struct *task;
        struct rq_wb *rwb;
-       struct rq_wait *rqw;
+       enum wbt_flags wb_acct;
        unsigned long rw;
-       bool got_token;
 };
 
-static int wbt_wake_function(struct wait_queue_entry *curr, unsigned int mode,
-                            int wake_flags, void *key)
+static bool wbt_inflight_cb(struct rq_wait *rqw, void *private_data)
 {
-       struct wbt_wait_data *data = container_of(curr, struct wbt_wait_data,
-                                                       wq);
-
-       /*
-        * If we fail to get a budget, return -1 to interrupt the wake up
-        * loop in __wake_up_common.
-        */
-       if (!rq_wait_inc_below(data->rqw, get_limit(data->rwb, data->rw)))
-               return -1;
+       struct wbt_wait_data *data = private_data;
+       return rq_wait_inc_below(rqw, get_limit(data->rwb, data->rw));
+}
 
-       data->got_token = true;
-       list_del_init(&curr->entry);
-       wake_up_process(data->task);
-       return 1;
+static void wbt_cleanup_cb(struct rq_wait *rqw, void *private_data)
+{
+       struct wbt_wait_data *data = private_data;
+       wbt_rqw_done(data->rwb, rqw, data->wb_acct);
 }
 
 /*
@@ -525,45 +515,12 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags 
wb_acct,
 {
        struct rq_wait *rqw = get_rq_wait(rwb, wb_acct);
        struct wbt_wait_data data = {
-               .wq = {
-                       .func   = wbt_wake_function,
-                       .entry  = LIST_HEAD_INIT(data.wq.entry),
-               },
-               .task = current,
                .rwb = rwb,
-               .rqw = rqw,
+               .wb_acct = wb_acct,
                .rw = rw,
        };
-       bool has_sleeper;
-
-       has_sleeper = wq_has_sleeper(&rqw->wait);
-       if (!has_sleeper && rq_wait_inc_below(rqw, get_limit(rwb, rw)))
-               return;
-
-       prepare_to_wait_exclusive(&rqw->wait, &data.wq, TASK_UNINTERRUPTIBLE);
-       do {
-               if (data.got_token)
-                       break;
-
-               if (!has_sleeper &&
-                   rq_wait_inc_below(rqw, get_limit(rwb, rw))) {
-                       finish_wait(&rqw->wait, &data.wq);
-
-                       /*
-                        * We raced with wbt_wake_function() getting a token,
-                        * which means we now have two. Put our local token
-                        * and wake anyone else potentially waiting for one.
-                        */
-                       if (data.got_token)
-                               wbt_rqw_done(rwb, rqw, wb_acct);
-                       break;
-               }
-
-               io_schedule();
-               has_sleeper = false;
-       } while (1);
 
-       finish_wait(&rqw->wait, &data.wq);
+       rq_qos_wait(rqw, &data, wbt_inflight_cb, wbt_cleanup_cb);
 }
 
 static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio)
-- 
2.14.3