[PATCH v2 07/11] md: change the type of nr_pending from atomic_t to percpu_ref

[tada keisuke]

This patch depends on patch 05.

Change the type of nr_pending from atomic_t to percpu_ref.
Additionally, temporarily switch from percpu mode to atomic mode.
This is to reduce the amount of changes from patches 8 to 10.
Patches 8 to 10 assume that nr_pending is run in percpu mode.
Finally, switch from atomic mode to percpu mode in patch 11.

Signed-off-by: Keisuke TADA <keisuke1.tada@xxxxxxxxxx>
Signed-off-by: Toshifumi OHTAKE <toshifumi.ootake@xxxxxxxxxx>
---
 drivers/md/md.c | 13 ++++++++++++-
 drivers/md/md.h | 18 +++++++++---------
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index d53ca23bacf7..7e6966e65d0d 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1002,6 +1002,7 @@ void md_rdev_clear(struct md_rdev *rdev)
 		put_page(rdev->bb_page);
 		rdev->bb_page = NULL;
 	}
+	percpu_ref_exit(&rdev->nr_pending);
 	badblocks_exit(&rdev->badblocks);
 }
 EXPORT_SYMBOL_GPL(md_rdev_clear);
@@ -3724,8 +3725,14 @@ static const struct kobj_type rdev_ktype = {
 	.default_groups	= rdev_default_groups,
 };
 
+static void percpu_wakeup_handle_req_pending(struct percpu_ref *ref)
+{
+}
+
 int md_rdev_init(struct md_rdev *rdev)
 {
+	int ret;
+
 	rdev->desc_nr = -1;
 	rdev->saved_raid_disk = -1;
 	rdev->raid_disk = -1;
@@ -3736,7 +3743,11 @@ int md_rdev_init(struct md_rdev *rdev)
 	rdev->last_read_error = 0;
 	rdev->sb_loaded = 0;
 	rdev->bb_page = NULL;
-	atomic_set(&rdev->nr_pending, 0);
+	ret = percpu_ref_init(&rdev->nr_pending, percpu_wakeup_handle_req_pending,
+		PERCPU_REF_ALLOW_REINIT, GFP_KERNEL);
+	WARN_ON(ret);
+	percpu_ref_switch_to_atomic_sync(&rdev->nr_pending);
+	nr_pending_dec(rdev);
 	atomic_set(&rdev->read_errors, 0);
 	atomic_set(&rdev->corrected_errors, 0);
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 783fec1f1445..ab09e312c9bb 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -107,10 +107,10 @@ struct md_rdev {
 					 */
 	};
 
-	atomic_t	nr_pending;	/* number of pending requests.
-					 * only maintained for arrays that
-					 * support hot removal
-					 */
+	struct percpu_ref	nr_pending;	/* number of pending requests.
+						 * only maintained for arrays that
+						 * support hot removal
+						 */
 	atomic_t	read_errors;	/* number of consecutive read errors that
 					 * we have tried to ignore.
 					 */
@@ -213,27 +213,27 @@ enum flag_bits {
 
 static inline void nr_pending_inc(struct md_rdev *rdev)
 {
-	atomic_inc(&rdev->nr_pending);
+	percpu_ref_get(&rdev->nr_pending);
 }
 
 static inline void nr_pending_dec(struct md_rdev *rdev)
 {
-	atomic_dec(&rdev->nr_pending);
+	percpu_ref_put(&rdev->nr_pending);
 }
 
 static inline bool nr_pending_is_zero(struct md_rdev *rdev)
 {
-	return atomic_read(&rdev->nr_pending) == 0;
+	return percpu_ref_is_zero(&rdev->nr_pending);
 }
 
 static inline bool nr_pending_is_not_zero(struct md_rdev *rdev)
 {
-	return atomic_read(&rdev->nr_pending) != 0;
+	return !percpu_ref_is_zero(&rdev->nr_pending);
 }
 
 static inline unsigned long nr_pending_read(struct md_rdev *rdev)
 {
-	return (unsigned long)atomic_read(&rdev->nr_pending);
+	return atomic_long_read(&rdev->nr_pending.data->count);
 }
 
 static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
-- 
2.34.1