md: Revert "md: Fix overflow in is_mddev_idle"

This reverts commit 3f9f231.

Using 64bit for 'sync_io' is unnecessary from the gendisk side. This
overflow will not cause any functional impact, except for a UBSAN
warning. Solving this overflow requires introducing additional
calculations and checks which are not necessary. So just keep using
32bit for 'sync_io'.

Signed-off-by: Li Nan <linan122@huawei.com>
Link: https://lore.kernel.org/r/20240507023103.781816-1-linan666@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/md.c

@@ -8577,7 +8577,7 @@ static int is_mddev_idle(struct mddev *mddev, int init)
 {
 	struct md_rdev *rdev;
 	int idle;
-	long long curr_events;
+	int curr_events;
 
 	idle = 1;
 	rcu_read_lock();
@@ -8587,9 +8587,8 @@ static int is_mddev_idle(struct mddev *mddev, int init)
 		if (!init && !blk_queue_io_stat(disk->queue))
 			continue;
 
-		curr_events =
-			(long long)part_stat_read_accum(disk->part0, sectors) -
-			atomic64_read(&disk->sync_io);
+		curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
+			      atomic_read(&disk->sync_io);
 		/* sync IO will cause sync_io to increase before the disk_stats
 		 * as sync_io is counted when a request starts, and
 		 * disk_stats is counted when it completes.

drivers/md/md.h

@@ -51,7 +51,7 @@ struct md_rdev {
 
 	sector_t sectors;		/* Device size (in 512bytes sectors) */
 	struct mddev *mddev;		/* RAID array if running */
-	long long last_events;		/* IO event timestamp */
+	int last_events;		/* IO event timestamp */
 
 	/*
 	 * If meta_bdev is non-NULL, it means that a separate device is
@@ -622,7 +622,7 @@ extern void mddev_unlock(struct mddev *mddev);
 static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
 {
 	if (blk_queue_io_stat(bdev->bd_disk->queue))
-		atomic64_add(nr_sectors, &bdev->bd_disk->sync_io);
+		atomic_add(nr_sectors, &bdev->bd_disk->sync_io);
 }
 
 static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)

include/linux/blkdev.h

@@ -172,7 +172,7 @@ struct gendisk {
 	struct list_head slave_bdevs;
 #endif
 	struct timer_rand_state *random;
-	atomic64_t sync_io;		/* RAID */
+	atomic_t sync_io;		/* RAID */
 	struct disk_events *ev;
 
 #ifdef CONFIG_BLK_DEV_ZONED