block: Fix list corruption of blk stats callback list

[sfrench/cifs-2.6.git] / block / blk-wbt.c

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 1aedb1f7ee0c7fde717d7701d3ee74cc90c21d17..b3b79149d3a0c61529983bb5e28e62f8c25d78a9 100644 (file)
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -255,8 +255,8 @@ static inline bool stat_sample_valid(struct blk_rq_stat *stat)
         * that it's writes impacting us, and not just some sole read on
         * a device that is in a lower power state.
         */
-       return stat[BLK_STAT_READ].nr_samples >= 1 &&
-               stat[BLK_STAT_WRITE].nr_samples >= RWB_MIN_WRITE_SAMPLES;
+       return (stat[READ].nr_samples >= 1 &&
+               stat[WRITE].nr_samples >= RWB_MIN_WRITE_SAMPLES);
 }
 
 static u64 rwb_sync_issue_lat(struct rq_wb *rwb)
@@ -277,7 +277,7 @@ enum {
        LAT_EXCEEDED,
 };
 
-static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
+static int latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
 {
        struct backing_dev_info *bdi = rwb->queue->backing_dev_info;
        u64 thislat;
@@ -293,7 +293,7 @@ static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
         */
        thislat = rwb_sync_issue_lat(rwb);
        if (thislat > rwb->cur_win_nsec ||
-           (thislat > rwb->min_lat_nsec && !stat[BLK_STAT_READ].nr_samples)) {
+           (thislat > rwb->min_lat_nsec && !stat[READ].nr_samples)) {
                trace_wbt_lat(bdi, thislat);
                return LAT_EXCEEDED;
        }
@@ -308,8 +308,8 @@ static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
                 * waited or still has writes in flights, consider us doing
                 * just writes as well.
                 */
-               if ((stat[BLK_STAT_WRITE].nr_samples && blk_stat_is_current(stat)) ||
-                   wb_recent_wait(rwb) || wbt_inflight(rwb))
+               if (stat[WRITE].nr_samples || wb_recent_wait(rwb) ||
+                   wbt_inflight(rwb))
                        return LAT_UNKNOWN_WRITES;
                return LAT_UNKNOWN;
        }
@@ -317,8 +317,8 @@ static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
        /*
         * If the 'min' latency exceeds our target, step down.
         */
-       if (stat[BLK_STAT_READ].min > rwb->min_lat_nsec) {
-               trace_wbt_lat(bdi, stat[BLK_STAT_READ].min);
+       if (stat[READ].min > rwb->min_lat_nsec) {
+               trace_wbt_lat(bdi, stat[READ].min);
                trace_wbt_stat(bdi, stat);
                return LAT_EXCEEDED;
        }
@@ -329,14 +329,6 @@ static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
        return LAT_OK;
 }
 
-static int latency_exceeded(struct rq_wb *rwb)
-{
-       struct blk_rq_stat stat[2];
-
-       blk_queue_stat_get(rwb->queue, stat);
-       return __latency_exceeded(rwb, stat);
-}
-
 static void rwb_trace_step(struct rq_wb *rwb, const char *msg)
 {
        struct backing_dev_info *bdi = rwb->queue->backing_dev_info;
@@ -355,7 +347,6 @@ static void scale_up(struct rq_wb *rwb)
 
        rwb->scale_step--;
        rwb->unknown_cnt = 0;
-       blk_stat_clear(rwb->queue);
 
        rwb->scaled_max = calc_wb_limits(rwb);
 
@@ -385,15 +376,12 @@ static void scale_down(struct rq_wb *rwb, bool hard_throttle)
 
        rwb->scaled_max = false;
        rwb->unknown_cnt = 0;
-       blk_stat_clear(rwb->queue);
        calc_wb_limits(rwb);
        rwb_trace_step(rwb, "step down");
 }
 
 static void rwb_arm_timer(struct rq_wb *rwb)
 {
-       unsigned long expires;
-
        if (rwb->scale_step > 0) {
                /*
                 * We should speed this up, using some variant of a fast
@@ -411,17 +399,16 @@ static void rwb_arm_timer(struct rq_wb *rwb)
                rwb->cur_win_nsec = rwb->win_nsec;
        }
 
-       expires = jiffies + nsecs_to_jiffies(rwb->cur_win_nsec);
-       mod_timer(&rwb->window_timer, expires);
+       blk_stat_activate_nsecs(rwb->cb, rwb->cur_win_nsec);
 }
 
-static void wb_timer_fn(unsigned long data)
+static void wb_timer_fn(struct blk_stat_callback *cb)
 {
-       struct rq_wb *rwb = (struct rq_wb *) data;
+       struct rq_wb *rwb = cb->data;
        unsigned int inflight = wbt_inflight(rwb);
        int status;
 
-       status = latency_exceeded(rwb);
+       status = latency_exceeded(rwb, cb->stat);
 
        trace_wbt_timer(rwb->queue->backing_dev_info, status, rwb->scale_step,
                        inflight);
@@ -614,7 +601,7 @@ enum wbt_flags wbt_wait(struct rq_wb *rwb, struct bio *bio, spinlock_t *lock)
 
        __wbt_wait(rwb, bio->bi_opf, lock);
 
-       if (!timer_pending(&rwb->window_timer))
+       if (!blk_stat_is_active(rwb->cb))
                rwb_arm_timer(rwb);
 
        if (current_is_kswapd())
@@ -666,19 +653,15 @@ void wbt_set_write_cache(struct rq_wb *rwb, bool write_cache_on)
                rwb->wc = write_cache_on;
 }
 
- /*
- * Disable wbt, if enabled by default. Only called from CFQ, if we have
- * cgroups enabled
+/*
+ * Disable wbt, if enabled by default. Only called from CFQ.
  */
 void wbt_disable_default(struct request_queue *q)
 {
        struct rq_wb *rwb = q->rq_wb;
 
-       if (rwb && rwb->enable_state == WBT_STATE_ON_DEFAULT) {
-               del_timer_sync(&rwb->window_timer);
-               rwb->win_nsec = rwb->min_lat_nsec = 0;
-               wbt_update_limits(rwb);
-       }
+       if (rwb && rwb->enable_state == WBT_STATE_ON_DEFAULT)
+               wbt_exit(q);
 }
 EXPORT_SYMBOL_GPL(wbt_disable_default);
 
@@ -699,24 +682,23 @@ int wbt_init(struct request_queue *q)
        struct rq_wb *rwb;
        int i;
 
-       /*
-        * For now, we depend on the stats window being larger than
-        * our monitoring window. Ensure that this isn't inadvertently
-        * violated.
-        */
-       BUILD_BUG_ON(RWB_WINDOW_NSEC > BLK_STAT_NSEC);
        BUILD_BUG_ON(WBT_NR_BITS > BLK_STAT_RES_BITS);
 
        rwb = kzalloc(sizeof(*rwb), GFP_KERNEL);
        if (!rwb)
                return -ENOMEM;
 
+       rwb->cb = blk_stat_alloc_callback(wb_timer_fn, blk_stat_rq_ddir, 2, rwb);
+       if (!rwb->cb) {
+               kfree(rwb);
+               return -ENOMEM;
+       }
+
        for (i = 0; i < WBT_NUM_RWQ; i++) {
                atomic_set(&rwb->rq_wait[i].inflight, 0);
                init_waitqueue_head(&rwb->rq_wait[i].wait);
        }
 
-       setup_timer(&rwb->window_timer, wb_timer_fn, (unsigned long) rwb);
        rwb->wc = 1;
        rwb->queue_depth = RWB_DEF_DEPTH;
        rwb->last_comp = rwb->last_issue = jiffies;
@@ -726,10 +708,10 @@ int wbt_init(struct request_queue *q)
        wbt_update_limits(rwb);
 
        /*
-        * Assign rwb, and turn on stats tracking for this queue
+        * Assign rwb and add the stats callback.
         */
        q->rq_wb = rwb;
-       blk_stat_enable(q);
+       blk_stat_add_callback(q, rwb->cb);
 
        rwb->min_lat_nsec = wbt_default_latency_nsec(q);
 
@@ -744,7 +726,8 @@ void wbt_exit(struct request_queue *q)
        struct rq_wb *rwb = q->rq_wb;
 
        if (rwb) {
-               del_timer_sync(&rwb->window_timer);
+               blk_stat_remove_callback(q, rwb->cb);
+               blk_stat_free_callback(rwb->cb);
                q->rq_wb = NULL;
                kfree(rwb);
        }