linux-kernel - Re: [PATCH v2 3/4] md/raid10: fix wrong setting of max_corr_read

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Message-ID: <5db8b619-7eac-79be-10e4-1292a44b943b@huaweicloud.com>
Date:   Sat, 13 May 2023 10:21:39 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Song Liu <song@...nel.org>, Yu Kuai <yukuai1@...weicloud.com>
Cc:     linan666@...weicloud.com, neilb@...e.de, Rob.Becker@...erbed.com,
        linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        linan122@...wei.com, yi.zhang@...wei.com, houtao1@...wei.com,
        yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2 3/4] md/raid10: fix wrong setting of
 max_corr_read_errors

Hi,

在 2023/05/13 9:08, Song Liu 写道:
> On Fri, May 5, 2023 at 7:02 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>>
>> Hi,
>>
>> 在 2023/05/06 9:23, linan666@...weicloud.com 写道:
>>> From: Li Nan <linan122@...wei.com>
>>>
>>> max_corr_read_errors should not be negative number. Change it to
>>> unsigned int where use it.
>>>
>>
>> Looks good, feel free to add:
>>
>> Reviewed-by: Yu Kuai <yukuai3@...wei.com>
>>
>>> Fixes: 1e50915fe0bb ("raid: improve MD/raid10 handling of correctable read errors.")
>>> Signed-off-by: Li Nan <linan122@...wei.com>
> 
> Hmm.. Does the current code break in any cases?

The problem is that somewhere use unsigned value, and somewhere use
signed value, and I thinsk the only functional change is in
fix_read_error(), if max_read_errors is negative, the judgement will
always pass before this patch:

if (atomic_read(&rdev->read_errors) > max_read_errors)

Thanks,
Kuai
> 
> Thanks,
> Song
> 
>>> ---
>>>    drivers/md/md.c     | 2 +-
>>>    drivers/md/raid10.c | 5 +++--
>>>    2 files changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>>> index fd5c3babcd6d..4a1e566d6bdc 100644
>>> --- a/drivers/md/md.c
>>> +++ b/drivers/md/md.c
>>> @@ -4486,7 +4486,7 @@ __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..4d615fcc6a50 100644
>>> --- a/drivers/md/raid10.c
>>> +++ b/drivers/md/raid10.c
>>> @@ -2727,7 +2727,8 @@ 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);
>>>        int d = r10_bio->devs[r10_bio->read_slot].devnum;
>>>
>>>        /* still own a reference to this rdev, so it cannot
>>> @@ -2743,7 +2744,7 @@ 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",
>>>
>>
> .
>