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>

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 */

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

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)