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Subject: Re: [PATCH 3/3] md/raid10: fix wrong setting of max_corr_read_errors
To:     linan666@huaweicloud.com, song@kernel.org, neilb@suse.de,
        Rob.Becker@riverbed.com
Cc:     linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
        linan122@huawei.com, yi.zhang@huawei.com, houtao1@huawei.com,
        yangerkun@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
References: <20230427085612.1346752-1-linan666@huaweicloud.com>
 <20230427085612.1346752-4-linan666@huaweicloud.com>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <686d8ef7-cbae-113c-fa48-e0c5dfa2f3d5@huaweicloud.com>
Date:   Thu, 27 Apr 2023 18:51:51 +0800
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Precedence: bulk

Hi,

?? 2023/04/27 16:56, linan666@huaweicloud.com д??:
> From: Li Nan <linan122@huawei.com>
> 
> max_corr_read_errors should not be negative number. Change it to
> unsigned int where use it.
> 
> Fixes: 1e50915fe0bb ("raid: improve MD/raid10 handling of correctable read errors.")
> Signed-off-by: Li Nan <linan122@huawei.com>
> ---
>   drivers/md/md.c     | 2 +-
>   drivers/md/raid10.c | 4 ++--
>   2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index faffbd042925..a365ed122960 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4484,7 +4484,7 @@ __ATTR_PREALLOC(array_state, S_IRUGO|S_IWUSR, array_state_show, array_state_stor
>   
>   static ssize_t
>   max_corrected_read_errors_show(struct mddev *mddev, char *page) {
> -	return sprintf(page, "%d\n",
> +	return sprintf(page, "%u\n",
>   		       atomic_read(&mddev->max_corr_read_errors));
>   }
>   
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 4fcfcb350d2b..28cdb2ae0e91 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -2727,7 +2727,7 @@ 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;
> -	int max_read_errors = atomic_read(&mddev->max_corr_read_errors);
> +	unsigned int max_read_errors = atomic_read(&mddev->max_corr_read_errors);

This line exceed 80 columns.
>   	int d = r10_bio->devs[r10_bio->read_slot].devnum;
>   
>   	/* still own a reference to this rdev, so it cannot
> @@ -2743,7 +2743,7 @@ static void fix_read_error(struct r10conf *conf, struct mddev *mddev, struct r10
>   	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 %d:max %d]\n",
> +		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",
> 

This is not critical, but I think it's better do some cleanup to fold
above code into check_decay_read_errors(), and rename it to
check_read_error():

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 7135cfaf75db..633aabfea452 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2636,18 +2636,17 @@ static void recovery_request_write(struct mddev 
*mddev, struct r10bio *r10_bio)
   * since the last recorded read error.
   *
   */
-static void check_decay_read_errors(struct mddev *mddev, struct md_rdev 
*rdev)
+static bool check_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;

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

         hours_since_last = (long)(cur_time_mon -
@@ -2660,10 +2659,26 @@ static void check_decay_read_errors(struct mddev 
*mddev, struct md_rdev *rdev)
          * 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);
+
+increase:
+       max_read_errors = atomic_read(&mddev->max_corr_read_errors);
+       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 true;
+       }
+
+       return false;
  }

  static int r10_sync_page_io(struct md_rdev *rdev, sector_t sector,
@@ -2703,7 +2718,6 @@ 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;
-       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
@@ -2716,15 +2730,7 @@ 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 %d:max %d]\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_read_errors(mddev, rdev)) {
                 r10_bio->devs[r10_bio->read_slot].bio = IO_BLOCKED;
                 return;
         }

Thanks,
Kuai