block: fix non-atomic access to genhd inflight structures

After the stack plugging introduction, these are called lockless.
Ensure that the counters are updated atomically.

Signed-off-by: Shaohua Li<shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

3 files changed, 12 insertions, 10 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 88820704a191..0cf68b478878 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -477,7 +477,8 @@ static void start_io_acct(struct dm_io *io)
         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]);
+        atomic_set(&dm_disk(md)->part0.in_flight[rw],
+                atomic_inc_return(&md->pending[rw]));
 }
 
 static void end_io_acct(struct dm_io *io)
@@ -497,8 +498,8 @@ static void end_io_acct(struct dm_io *io)
          * After this is decremented the bio must not be touched if it is
          * a flush.
          */
-        dm_disk(md)->part0.in_flight[rw] = pending =
-                atomic_dec_return(&md->pending[rw]);
+        pending = atomic_dec_return(&md->pending[rw]);
+        atomic_set(&dm_disk(md)->part0.in_flight[rw], pending);
         pending += atomic_read(&md->pending[rw^0x1]);
 
         /* nudge anyone waiting on suspend queue */
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 9c21119512b9..ac546975031f 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -290,7 +290,8 @@ ssize_t part_inflight_show(struct device *dev,
 {
         struct hd_struct *p = dev_to_part(dev);
 
-        return sprintf(buf, "%8u %8u\n", p->in_flight[0], p->in_flight[1]);
+        return sprintf(buf, "%8u %8u\n", atomic_read(&p->in_flight[0]),
+                atomic_read(&p->in_flight[1]));
 }
 
 #ifdef CONFIG_FAIL_MAKE_REQUEST
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index c0d5f6945c1e..d764a426e9fd 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -109,7 +109,7 @@ struct hd_struct {
         int make_it_fail;
 #endif
         unsigned long stamp;
-        int in_flight[2];
+        atomic_t in_flight[2];
 #ifdef  CONFIG_SMP
         struct disk_stats __percpu *dkstats;
 #else
@@ -370,21 +370,21 @@ static inline void free_part_stats(struct hd_struct *part)
 
 static inline void part_inc_in_flight(struct hd_struct *part, int rw)
 {
-        part->in_flight[rw]++;
+        atomic_inc(&part->in_flight[rw]);
         if (part->partno)
-                part_to_disk(part)->part0.in_flight[rw]++;
+                atomic_inc(&part_to_disk(part)->part0.in_flight[rw]);
 }
 
 static inline void part_dec_in_flight(struct hd_struct *part, int rw)
 {
-        part->in_flight[rw]--;
+        atomic_dec(&part->in_flight[rw]);
         if (part->partno)
-                part_to_disk(part)->part0.in_flight[rw]--;
+                atomic_dec(&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];
+        return atomic_read(&part->in_flight[0]) + atomic_read(&part->in_flight[1]);
 }
 
 static inline struct partition_meta_info *alloc_part_info(struct gendisk *disk)