Revert "Seperate read and write statistics of in_flight requests"

This reverts commit a9327cac440be4d8333bba975cbbf76045096275.

Corrado Zoccolo <czoccolo@gmail.com> reports:

"with 2.6.32-rc1 I started getting the following strange output from
"iostat -kx 2":
Linux 2.6.31bisect (et2) 	04/10/2009 	_i686_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          10,70    0,00    3,16   15,75    0,00   70,38

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda              18,22     0,00    0,67    0,01    14,77     0,02
43,94     0,01   10,53 39043915,03 2629219,87
sdb              60,89     9,68   50,79    3,04  1724,43    50,52
65,95     0,70   13,06 488437,47 2629219,87

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           2,72    0,00    0,74    0,00    0,00   96,53

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           6,68    0,00    0,99    0,00    0,00   92,33

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           4,40    0,00    0,73    1,47    0,00   93,40

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     4,00    0,00    3,00     0,00    28,00
18,67     0,06   19,50 333,33 100,00

Global values for service time and utilization are garbage. For
interval values, utilization is always 100%, and service time is
higher than normal.

I bisected it down to:
[a9327cac440be4d8333bba975cbbf76045096275] Seperate read and write
statistics of in_flight requests
and verified that reverting just that commit indeed solves the issue
on 2.6.32-rc1."

So until this is debugged, revert the bad commit.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

6 files changed, 19 insertions, 42 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index a8c7fbe52e24..81f34311659a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -70,7 +70,7 @@ static void drive_stat_acct(struct request *rq, int new_io)
                 part_stat_inc(cpu, part, merges[rw]);
         else {
                 part_round_stats(cpu, part);
-                part_inc_in_flight(part, rw);
+                part_inc_in_flight(part);
         }
 
         part_stat_unlock();
@@ -1032,7 +1032,7 @@ static void part_round_stats_single(int cpu, struct hd_struct *part,
 
         if (part->in_flight) {
                 __part_stat_add(cpu, part, time_in_queue,
-                                part_in_flight(part) * (now - part->stamp));
+                                part->in_flight * (now - part->stamp));
                 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
         }
         part->stamp = now;
@@ -1739,7 +1739,7 @@ static void blk_account_io_done(struct request *req)
                 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, rw);
+                part_dec_in_flight(part);
 
                 part_stat_unlock();
         }
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 99cb5cf1f447..b0de8574fdc8 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -351,7 +351,7 @@ static void blk_account_io_merge(struct request *req)
                 part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
 
                 part_round_stats(cpu, part);
-                part_dec_in_flight(part, rq_data_dir(req));
+                part_dec_in_flight(part);
 
                 part_stat_unlock();
         }
diff --git a/block/genhd.c b/block/genhd.c
index 517e4332cb37..5a0861da324d 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -869,7 +869,6 @@ static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
 static DEVICE_ATTR(alignment_offset, S_IRUGO, disk_alignment_offset_show, NULL);
 static DEVICE_ATTR(capability, S_IRUGO, disk_capability_show, NULL);
 static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
-static DEVICE_ATTR(inflight, S_IRUGO, part_inflight_show, NULL);
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 static struct device_attribute dev_attr_fail =
         __ATTR(make-it-fail, S_IRUGO|S_IWUSR, part_fail_show, part_fail_store);
@@ -889,7 +888,6 @@ static struct attribute *disk_attrs[] = {
         &dev_attr_alignment_offset.attr,
         &dev_attr_capability.attr,
         &dev_attr_stat.attr,
-        &dev_attr_inflight.attr,
 #ifdef CONFIG_FAIL_MAKE_REQUEST
         &dev_attr_fail.attr,
 #endif
@@ -1055,7 +1053,7 @@ static int diskstats_show(struct seq_file *seqf, void *v)
                            part_stat_read(hd, merges[1]),
                            (unsigned long long)part_stat_read(hd, sectors[1]),
                            jiffies_to_msecs(part_stat_read(hd, ticks[1])),
-                           part_in_flight(hd),
+                           hd->in_flight,
                            jiffies_to_msecs(part_stat_read(hd, io_ticks)),
                            jiffies_to_msecs(part_stat_read(hd, time_in_queue))
                         );
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 376f1ab48a24..23e76fe0d359 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -130,7 +130,7 @@ struct mapped_device {
         /*
          * A list of ios that arrived while we were suspended.
          */
-        atomic_t pending[2];
+        atomic_t pending;
         wait_queue_head_t wait;
         struct work_struct work;
         struct bio_list deferred;
@@ -453,14 +453,13 @@ static void start_io_acct(struct dm_io *io)
 {
         struct mapped_device *md = io->md;
         int cpu;
-        int rw = bio_data_dir(io->bio);
 
         io->start_time = jiffies;
 
         cpu = part_stat_lock();
         part_round_stats(cpu, &dm_disk(md)->part0);
         part_stat_unlock();
-        dm_disk(md)->part0.in_flight[rw] = atomic_inc_return(&md->pending[rw]);
+        dm_disk(md)->part0.in_flight = atomic_inc_return(&md->pending);
 }
 
 static void end_io_acct(struct dm_io *io)
@@ -480,9 +479,8 @@ static void end_io_acct(struct dm_io *io)
          * After this is decremented the bio must not be touched if it is
          * a barrier.
          */
-        dm_disk(md)->part0.in_flight[rw] = pending =
-                atomic_dec_return(&md->pending[rw]);
-        pending += atomic_read(&md->pending[rw^0x1]);
+        dm_disk(md)->part0.in_flight = pending =
+                atomic_dec_return(&md->pending);
 
         /* nudge anyone waiting on suspend queue */
         if (!pending)
@@ -1787,8 +1785,7 @@ static struct mapped_device *alloc_dev(int minor)
         if (!md->disk)
                 goto bad_disk;
 
-        atomic_set(&md->pending[0], 0);
-        atomic_set(&md->pending[1], 0);
+        atomic_set(&md->pending, 0);
         init_waitqueue_head(&md->wait);
         INIT_WORK(&md->work, dm_wq_work);
         init_waitqueue_head(&md->eventq);
@@ -2091,8 +2088,7 @@ static int dm_wait_for_completion(struct mapped_device *md, int interruptible)
                                 break;
                         }
                         spin_unlock_irqrestore(q->queue_lock, flags);
-                } else if (!atomic_read(&md->pending[0]) &&
-                                        !atomic_read(&md->pending[1]))
+                } else if (!atomic_read(&md->pending))
                         break;
 
                 if (interruptible == TASK_INTERRUPTIBLE &&
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 7b685e10cbad..f38fee0311a7 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -248,19 +248,11 @@ ssize_t part_stat_show(struct device *dev,
                 part_stat_read(p, merges[WRITE]),
                 (unsigned long long)part_stat_read(p, sectors[WRITE]),
                 jiffies_to_msecs(part_stat_read(p, ticks[WRITE])),
-                part_in_flight(p),
+                p->in_flight,
                 jiffies_to_msecs(part_stat_read(p, io_ticks)),
                 jiffies_to_msecs(part_stat_read(p, time_in_queue)));
 }
 
-ssize_t part_inflight_show(struct device *dev,
-                        struct device_attribute *attr, char *buf)
-{
-        struct hd_struct *p = dev_to_part(dev);
-
-        return sprintf(buf, "%8u %8u\n", p->in_flight[0], p->in_flight[1]);
-}
-
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 ssize_t part_fail_show(struct device *dev,
                        struct device_attribute *attr, char *buf)
@@ -289,7 +281,6 @@ static DEVICE_ATTR(start, S_IRUGO, part_start_show, NULL);
 static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
 static DEVICE_ATTR(alignment_offset, S_IRUGO, part_alignment_offset_show, NULL);
 static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
-static DEVICE_ATTR(inflight, S_IRUGO, part_inflight_show, NULL);
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 static struct device_attribute dev_attr_fail =
         __ATTR(make-it-fail, S_IRUGO|S_IWUSR, part_fail_show, part_fail_store);
@@ -301,7 +292,6 @@ static struct attribute *part_attrs[] = {
         &dev_attr_size.attr,
         &dev_attr_alignment_offset.attr,
         &dev_attr_stat.attr,
-        &dev_attr_inflight.attr,
 #ifdef CONFIG_FAIL_MAKE_REQUEST
         &dev_attr_fail.attr,
 #endif
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 297df45ffd0a..7beaa21b3880 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -98,7 +98,7 @@ struct hd_struct {
         int make_it_fail;
 #endif
         unsigned long stamp;
-        int in_flight[2];
+        int in_flight;
 #ifdef  CONFIG_SMP
         struct disk_stats *dkstats;
 #else
@@ -322,23 +322,18 @@ static inline void free_part_stats(struct hd_struct *part)
 #define part_stat_sub(cpu, gendiskp, field, subnd)                      \
         part_stat_add(cpu, gendiskp, field, -subnd)
 
-static inline void part_inc_in_flight(struct hd_struct *part, int rw)
+static inline void part_inc_in_flight(struct hd_struct *part)
 {
-        part->in_flight[rw]++;
+        part->in_flight++;
         if (part->partno)
-                part_to_disk(part)->part0.in_flight[rw]++;
+                part_to_disk(part)->part0.in_flight++;
 }
 
-static inline void part_dec_in_flight(struct hd_struct *part, int rw)
+static inline void part_dec_in_flight(struct hd_struct *part)
 {
-        part->in_flight[rw]--;
+        part->in_flight--;
         if (part->partno)
-                part_to_disk(part)->part0.in_flight[rw]--;
-}
-
-static inline int part_in_flight(struct hd_struct *part)
-{
-        return part->in_flight[0] + part->in_flight[1];
+                part_to_disk(part)->part0.in_flight--;
 }
 
 /* block/blk-core.c */
@@ -551,8 +546,6 @@ extern ssize_t part_size_show(struct device *dev,
                               struct device_attribute *attr, char *buf);
 extern ssize_t part_stat_show(struct device *dev,
                               struct device_attribute *attr, char *buf);
-extern ssize_t part_inflight_show(struct device *dev,
-                              struct device_attribute *attr, char *buf);
 #ifdef CONFIG_FAIL_MAKE_REQUEST
 extern ssize_t part_fail_show(struct device *dev,
                               struct device_attribute *attr, char *buf);