On Tue, Nov 30, 2021 at 6:56 PM Li Jinlin <lijinlin3@xxxxxxxxxx> wrote:
>
> The value of curr_events may be INT_MAX when mddev initializes IO event
> counters. Then, rdev->last_events will be set as INT_MAX.
> If all the rdevs of mddev are in this case,
> 'curr_events - rdev->last_events > 64' will always false, and
> is_mddev_idle() will always return 1, which may cause non-sync IO very
> slow.
>
> Fix by using atomic64_t type for sync_io, and using long type for
> curr_events/last_events.
>
> Signed-off-by: Li Jinlin <lijinlin3@xxxxxxxxxx>
> ---
> drivers/md/md.c | 6 +++---
> drivers/md/md.h | 4 ++--
> include/linux/genhd.h | 2 +-
> 3 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 5111ed966947..f47035838c43 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -8429,14 +8429,14 @@ static int is_mddev_idle(struct mddev *mddev, int init)
> {
> struct md_rdev *rdev;
> int idle;
> - int curr_events;
> + long curr_events;
>
> idle = 1;
> rcu_read_lock();
> rdev_for_each_rcu(rdev, mddev) {
> struct gendisk *disk = rdev->bdev->bd_disk;
> - curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
> - atomic_read(&disk->sync_io);
> + curr_events = (long)part_stat_read_accum(disk->part0, sectors) -
> + atomic64_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.
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 53ea7a6961de..3f8327c42b7b 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -50,7 +50,7 @@ struct md_rdev {
>
> sector_t sectors; /* Device size (in 512bytes sectors) */
> struct mddev *mddev; /* RAID array if running */
> - int last_events; /* IO event timestamp */
> + long last_events; /* IO event timestamp */
I think we need long long here to be safe on 32-bit systems.
Thanks,
Song
