2023-05-06 01:32:06

by Li Nan

Subject: [PATCH v2 4/4] md/raid10: optimize check_decay_read_errors()

From: Li Nan <[email protected]>

check_decay_read_errors() is used to handle rdev->read_errors. But
read_errors is inc and read after check_decay_read_errors() is invoked
in fix_read_error().

Put all operations of read_errors into check_decay_read_errors() and
clean up unnecessary atomic_read of read_errors.

Suggested-by: Yu Kuai <[email protected]>
Signed-off-by: Li Nan <[email protected]>
---
drivers/md/raid10.c | 66 ++++++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 31 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 4d615fcc6a50..79f94882227d 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2655,39 +2655,53 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
}

/*
- * Used by fix_read_error() to decay the per rdev read_errors.
+ * Used by fix_read_error() to decay the per rdev read_errors and check if
+ * read_error > max_read_errors.
* We halve the read error count for every hour that has elapsed
* since the last recorded read error.
*
*/
-static void check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev)
+static bool check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev)
{
- long cur_time_mon;
+ time64_t cur_time_mon = ktime_get_seconds();
unsigned long hours_since_last;
- unsigned int read_errors = atomic_read(&rdev->read_errors);
-
- cur_time_mon = ktime_get_seconds();
+ unsigned int read_errors;
+ unsigned int max_read_errors =
+ atomic_read(&mddev->max_corr_read_errors);

if (rdev->last_read_error == 0) {
/* first time we've seen a read error */
rdev->last_read_error = cur_time_mon;
- return;
- }
+ } else {
+ hours_since_last = (long)(cur_time_mon -
+ rdev->last_read_error) / 3600;

- hours_since_last = (long)(cur_time_mon -
- rdev->last_read_error) / 3600;
+ rdev->last_read_error = cur_time_mon;

- rdev->last_read_error = cur_time_mon;
+ /*
+ * if hours_since_last is > the number of bits in read_errors
+ * just set read errors to 0. We do this to avoid
+ * overflowing the shift of read_errors by hours_since_last.
+ */
+ read_errors = atomic_read(&rdev->read_errors);
+ if (hours_since_last >= 8 * sizeof(read_errors))
+ atomic_set(&rdev->read_errors, 0);
+ else
+ atomic_set(&rdev->read_errors,
+ read_errors >> hours_since_last);
+ }

- /*
- * if hours_since_last is > the number of bits in read_errors
- * just set read errors to 0. We do this to avoid
- * overflowing the shift of read_errors by hours_since_last.
- */
- if (hours_since_last >= 8 * sizeof(read_errors))
- atomic_set(&rdev->read_errors, 0);
- else
- atomic_set(&rdev->read_errors, read_errors >> hours_since_last);
+ read_errors = atomic_inc_return(&rdev->read_errors);
+ if (read_errors > max_read_errors) {
+ pr_notice("md/raid10:%s: %pg: Raid device exceeded read_error threshold [cur %u:max %u]\n",
+ mdname(mddev), rdev->bdev, read_errors, max_read_errors);
+ pr_notice("md/raid10:%s: %pg: Failing raid device\n",
+ mdname(mddev), rdev->bdev);
+ md_error(mddev, rdev);
+ return false;
+ }
+
+ return true;
}

static int r10_sync_page_io(struct md_rdev *rdev, sector_t sector,
@@ -2727,8 +2741,6 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10
int sect = 0; /* Offset from r10_bio->sector */
int sectors = r10_bio->sectors;
struct md_rdev *rdev;
- unsigned int max_read_errors =
- atomic_read(&mddev->max_corr_read_errors);
int d = r10_bio->devs[r10_bio->read_slot].devnum;

/* still own a reference to this rdev, so it cannot
@@ -2741,15 +2753,7 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10
more fix_read_error() attempts */
return;

- check_decay_read_errors(mddev, rdev);
- atomic_inc(&rdev->read_errors);
- if (atomic_read(&rdev->read_errors) > max_read_errors) {
- pr_notice("md/raid10:%s: %pg: Raid device exceeded read_error threshold [cur %u:max %u]\n",
- mdname(mddev), rdev->bdev,
- atomic_read(&rdev->read_errors), max_read_errors);
- pr_notice("md/raid10:%s: %pg: Failing raid device\n",
- mdname(mddev), rdev->bdev);
- md_error(mddev, rdev);
+ if (check_decay_read_errors(mddev, rdev)) {
r10_bio->devs[r10_bio->read_slot].bio = IO_BLOCKED;
return;
}
--
2.31.1

2023-05-06 02:21:11

by Yu Kuai

Subject: Re: [PATCH v2 4/4] md/raid10: optimize check_decay_read_errors()

Hi,

?? 2023/05/06 9:23, [email protected] д??:
> From: Li Nan <[email protected]>
>
> check_decay_read_errors() is used to handle rdev->read_errors. But
> read_errors is inc and read after check_decay_read_errors() is invoked
> in fix_read_error().
>
> Put all operations of read_errors into check_decay_read_errors() and
> clean up unnecessary atomic_read of read_errors.
>
> Suggested-by: Yu Kuai <[email protected]>
> Signed-off-by: Li Nan <[email protected]>
> ---
> drivers/md/raid10.c | 66 ++++++++++++++++++++++++---------------------
> 1 file changed, 35 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 4d615fcc6a50..79f94882227d 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -2655,39 +2655,53 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
> }
>
> /*
> - * Used by fix_read_error() to decay the per rdev read_errors.
> + * Used by fix_read_error() to decay the per rdev read_errors and check if
> + * read_error > max_read_errors.
> * We halve the read error count for every hour that has elapsed
> * since the last recorded read error.
> *
> */
> -static void check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev)
> +static bool check_decay_read_errors(struct mddev *mddev, struct md_rdev *rdev)
> {
> - long cur_time_mon;
> + time64_t cur_time_mon = ktime_get_seconds();
> unsigned long hours_since_last;
> - unsigned int read_errors = atomic_read(&rdev->read_errors);
> -
> - cur_time_mon = ktime_get_seconds();
> + unsigned int read_errors;
> + unsigned int max_read_errors =
> + atomic_read(&mddev->max_corr_read_errors);
>
> if (rdev->last_read_error == 0) {
> /* first time we've seen a read error */
> rdev->last_read_error = cur_time_mon;
> - return;
> - }

I prefer to use a goto tag here, so that following code doesn't need to
be changed. Other than that, this patch looks good to me.

Thanks,
Kuai
> + } else {
> + hours_since_last = (long)(cur_time_mon -
> + rdev->last_read_error) / 3600;
>
> - hours_since_last = (long)(cur_time_mon -
> - rdev->last_read_error) / 3600;
> + rdev->last_read_error = cur_time_mon;
>
> - rdev->last_read_error = cur_time_mon;
> + /*
> + * if hours_since_last is > the number of bits in read_errors
> + * just set read errors to 0. We do this to avoid
> + * overflowing the shift of read_errors by hours_since_last.
> + */
> + read_errors = atomic_read(&rdev->read_errors);
> + if (hours_since_last >= 8 * sizeof(read_errors))
> + atomic_set(&rdev->read_errors, 0);
> + else
> + atomic_set(&rdev->read_errors,
> + read_errors >> hours_since_last);
> + }
>
> - /*
> - * if hours_since_last is > the number of bits in read_errors
> - * just set read errors to 0. We do this to avoid
> - * overflowing the shift of read_errors by hours_since_last.
> - */
> - if (hours_since_last >= 8 * sizeof(read_errors))
> - atomic_set(&rdev->read_errors, 0);
> - else
> - atomic_set(&rdev->read_errors, read_errors >> hours_since_last);
> + read_errors = atomic_inc_return(&rdev->read_errors);
> + if (read_errors > max_read_errors) {
> + pr_notice("md/raid10:%s: %pg: Raid device exceeded read_error threshold [cur %u:max %u]\n",
> + mdname(mddev), rdev->bdev, read_errors, max_read_errors);
> + pr_notice("md/raid10:%s: %pg: Failing raid device\n",
> + mdname(mddev), rdev->bdev);
> + md_error(mddev, rdev);
> + return false;
> + }
> +
> + return true;
> }
>
> static int r10_sync_page_io(struct md_rdev *rdev, sector_t sector,
> @@ -2727,8 +2741,6 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10
> int sect = 0; /* Offset from r10_bio->sector */
> int sectors = r10_bio->sectors;
> struct md_rdev *rdev;
> - unsigned int max_read_errors =
> - atomic_read(&mddev->max_corr_read_errors);
> int d = r10_bio->devs[r10_bio->read_slot].devnum;
>
> /* still own a reference to this rdev, so it cannot
> @@ -2741,15 +2753,7 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10
> more fix_read_error() attempts */
> return;
>
> - check_decay_read_errors(mddev, rdev);
> - atomic_inc(&rdev->read_errors);
> - if (atomic_read(&rdev->read_errors) > max_read_errors) {
> - pr_notice("md/raid10:%s: %pg: Raid device exceeded read_error threshold [cur %u:max %u]\n",
> - mdname(mddev), rdev->bdev,
> - atomic_read(&rdev->read_errors), max_read_errors);
> - pr_notice("md/raid10:%s: %pg: Failing raid device\n",
> - mdname(mddev), rdev->bdev);
> - md_error(mddev, rdev);
> + if (check_decay_read_errors(mddev, rdev)) {
> r10_bio->devs[r10_bio->read_slot].bio = IO_BLOCKED;
> return;
> }
>