block: move stats from disk to part0

Move stats related fields - stamp, in_flight, dkstats - from disk to
part0 and unify stat handling such that...

* part_stat_*() now updates part0 together if the specified partition
  is not part0.  ie. part_stat_*() are now essentially all_stat_*().

* {disk|all}_stat_*() are gone.

* part_round_stats() is updated similary.  It handles part0 stats
  automatically and disk_round_stats() is killed.

* part_{inc|dec}_in_fligh() is implemented which automatically updates
  part0 stats for parts other than part0.

* disk_map_sector_rcu() is updated to return part0 if no part matches.
  Combined with the above changes, this makes NULL special case
  handling in callers unnecessary.

* Separate stats show code paths for disk are collapsed into part
  stats show code paths.

* Rename disk_stat_lock/unlock() to part_stat_lock/unlock()

While at it, reposition stat handling macros a bit and add missing
parentheses around macro parameters.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 34 insertions, 50 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 505ec61067df..98138f002524 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -61,21 +61,17 @@ static void drive_stat_acct(struct request *rq, int new_io)
         if (!blk_fs_request(rq) || !rq->rq_disk)
                 return;
 
-        cpu = disk_stat_lock();
+        cpu = part_stat_lock();
         part = disk_map_sector_rcu(rq->rq_disk, rq->sector);
 
         if (!new_io)
-                all_stat_inc(cpu, rq->rq_disk, part, merges[rw], rq->sector);
+                part_stat_inc(cpu, part, merges[rw]);
         else {
-                disk_round_stats(cpu, rq->rq_disk);
-                rq->rq_disk->in_flight++;
-                if (part) {
-                        part_round_stats(cpu, part);
-                        part->in_flight++;
-                }
+                part_round_stats(cpu, part);
+                part_inc_in_flight(part);
         }
 
-        disk_stat_unlock();
+        part_stat_unlock();
 }
 
 void blk_queue_congestion_threshold(struct request_queue *q)
@@ -983,8 +979,22 @@ static inline void add_request(struct request_queue *q, struct request *req)
         __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
 }
 
-/*
- * disk_round_stats()   - Round off the performance stats on a struct
+static void part_round_stats_single(int cpu, struct hd_struct *part,
+                                    unsigned long now)
+{
+        if (now == part->stamp)
+                return;
+
+        if (part->in_flight) {
+                __part_stat_add(cpu, part, time_in_queue,
+                                part->in_flight * (now - part->stamp));
+                __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
+        }
+        part->stamp = now;
+}
+
+/**
+ * part_round_stats()   - Round off the performance stats on a struct
  * disk_stats.
  *
  * The average IO queue length and utilisation statistics are maintained
@@ -998,36 +1008,15 @@ static inline void add_request(struct request_queue *q, struct request *req)
  * /proc/diskstats.  This accounts immediately for all queue usage up to
  * the current jiffies and restarts the counters again.
  */
-void disk_round_stats(int cpu, struct gendisk *disk)
-{
-        unsigned long now = jiffies;
-
-        if (now == disk->stamp)
-                return;
-
-        if (disk->in_flight) {
-                disk_stat_add(cpu, disk, time_in_queue,
-                              disk->in_flight * (now - disk->stamp));
-                disk_stat_add(cpu, disk, io_ticks, (now - disk->stamp));
-        }
-        disk->stamp = now;
-}
-EXPORT_SYMBOL_GPL(disk_round_stats);
-
 void part_round_stats(int cpu, struct hd_struct *part)
 {
         unsigned long now = jiffies;
 
-        if (now == part->stamp)
-                return;
-
-        if (part->in_flight) {
-                part_stat_add(cpu, part, time_in_queue,
-                              part->in_flight * (now - part->stamp));
-                part_stat_add(cpu, part, io_ticks, (now - part->stamp));
-        }
-        part->stamp = now;
+        if (part->partno)
+                part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
+        part_round_stats_single(cpu, part, now);
 }
+EXPORT_SYMBOL_GPL(part_round_stats);
 
 /*
  * queue lock must be held
@@ -1567,11 +1556,10 @@ static int __end_that_request_first(struct request *req, int error,
                 struct hd_struct *part;
                 int cpu;
 
-                cpu = disk_stat_lock();
+                cpu = part_stat_lock();
                 part = disk_map_sector_rcu(req->rq_disk, req->sector);
-                all_stat_add(cpu, req->rq_disk, part, sectors[rw],
-                             nr_bytes >> 9, req->sector);
-                disk_stat_unlock();
+                part_stat_add(cpu, part, sectors[rw], nr_bytes >> 9);
+                part_stat_unlock();
         }
 
         total_bytes = bio_nbytes = 0;
@@ -1758,19 +1746,15 @@ static void end_that_request_last(struct request *req, int error)
                 struct hd_struct *part;
                 int cpu;
 
-                cpu = disk_stat_lock();
+                cpu = part_stat_lock();
                 part = disk_map_sector_rcu(disk, req->sector);
 
-                all_stat_inc(cpu, disk, part, ios[rw], req->sector);
-                all_stat_add(cpu, disk, part, ticks[rw], duration, req->sector);
-                disk_round_stats(cpu, disk);
-                disk->in_flight--;
-                if (part) {
-                        part_round_stats(cpu, part);
-                        part->in_flight--;
-                }
+                part_stat_inc(cpu, part, ios[rw]);
+                part_stat_add(cpu, part, ticks[rw], duration);
+                part_round_stats(cpu, part);
+                part_dec_in_flight(part);
 
-                disk_stat_unlock();
+                part_stat_unlock();
         }
 
         if (req->end_io)