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 <[email protected]>
---
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 */
sync_io
/*
* If meta_bdev is non-NULL, it means that a separate device is
@@ -551,7 +551,7 @@ extern void mddev_unlock(struct mddev *mddev);
static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
{
- atomic_add(nr_sectors, &bdev->bd_disk->sync_io);
+ atomic64_add(nr_sectors, &bdev->bd_disk->sync_io);
}
static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 74c410263113..efa7884de11b 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -150,7 +150,7 @@ struct gendisk {
struct list_head slave_bdevs;
#endif
struct timer_rand_state *random;
- atomic_t sync_io; /* RAID */
+ atomic64_t sync_io; /* RAID */
struct disk_events *ev;
#ifdef CONFIG_BLK_DEV_INTEGRITY
struct kobject integrity_kobj;
--
2.31.1
On Wed, Dec 01, 2021 at 11:27:12AM +0800, Li Jinlin wrote:
> 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);
And what makes you believe you might not have to go and change all other
drivers to address this as well?
> static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
> index 74c410263113..efa7884de11b 100644
> --- a/include/linux/genhd.h
> +++ b/include/linux/genhd.h
> @@ -150,7 +150,7 @@ struct gendisk {
> struct list_head slave_bdevs;
> #endif
> struct timer_rand_state *random;
> - atomic_t sync_io; /* RAID */
> + atomic64_t sync_io; /* RAID */
> struct disk_events *ev;
> #ifdef CONFIG_BLK_DEV_INTEGRITY
> struct kobject integrity_kobj;
> --
> 2.31.1
Luis
On 12/1/2021 9:50 PM, Luis Chamberlain wrote:
> On Wed, Dec 01, 2021 at 11:27:12AM +0800, Li Jinlin wrote:
>> 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);
>
> And what makes you believe you might not have to go and change all other
> drivers to address this as well?
The drdb driver also have same problem. I will resend this patch together with
the fix patch of drdb driver.
Thanks,
JinLin
>
>> static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
>> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
>> index 74c410263113..efa7884de11b 100644
>> --- a/include/linux/genhd.h
>> +++ b/include/linux/genhd.h
>> @@ -150,7 +150,7 @@ struct gendisk {
>> struct list_head slave_bdevs;
>> #endif
>> struct timer_rand_state *random;
>> - atomic_t sync_io; /* RAID */
>> + atomic64_t sync_io; /* RAID */
>> struct disk_events *ev;
>> #ifdef CONFIG_BLK_DEV_INTEGRITY
>> struct kobject integrity_kobj;
>> --
>> 2.31.1
>
> Luis
> .
>
On Tue, Nov 30, 2021 at 6:56 PM Li Jinlin <[email protected]> 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 <[email protected]>
> ---
> 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