[PATCH -next] raid10: fix leak of io accounting

[PATCH -next] raid10: fix leak of io accounting

[Yu Kuai]

From: Yu Kuai <yukuai3@huawei.com>

handle_read_error() will resumit r10_bio by raid10_read_request(), which
will call bio_start_io_acct() again, while bio_end_io_acct() will only
be called once.

Fix the problem by don't account io again from handle_read_error().

Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 drivers/md/raid10.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 6c66357f92f5..4f8edb6ea3e2 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1173,7 +1173,7 @@ static bool regular_request_wait(struct mddev *mddev, struct r10conf *conf,
 }
 
 static void raid10_read_request(struct mddev *mddev, struct bio *bio,
-				struct r10bio *r10_bio)
+				struct r10bio *r10_bio, bool handle_error)
 {
 	struct r10conf *conf = mddev->private;
 	struct bio *read_bio;
@@ -1244,7 +1244,7 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
 	}
 	slot = r10_bio->read_slot;
 
-	if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
+	if (!handle_error && blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
 		r10_bio->start_time = bio_start_io_acct(bio);
 	read_bio = bio_alloc_clone(rdev->bdev, bio, gfp, &mddev->bio_set);
 
@@ -1578,7 +1578,7 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
 			conf->geo.raid_disks);
 
 	if (bio_data_dir(bio) == READ)
-		raid10_read_request(mddev, bio, r10_bio);
+		raid10_read_request(mddev, bio, r10_bio, false);
 	else
 		raid10_write_request(mddev, bio, r10_bio);
 }
@@ -2980,7 +2980,7 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
 	rdev_dec_pending(rdev, mddev);
 	allow_barrier(conf);
 	r10_bio->state = 0;
-	raid10_read_request(mddev, r10_bio->master_bio, r10_bio);
+	raid10_read_request(mddev, r10_bio->master_bio, r10_bio, true);
 }
 
 static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)
-- 
2.31.1

Re: [PATCH -next] raid10: fix leak of io accounting

[Guoqing Jiang]

Hi,

What do you mean 'leak' here?

On 3/4/23 15:01, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
>
> handle_read_error() will resumit r10_bio by raid10_read_request(), which
> will call bio_start_io_acct() again, while bio_end_io_acct() will only
> be called once.
>
> Fix the problem by don't account io again from handle_read_error().

My understanding is it caused inaccurate io stats for bio which had a read
error.

> Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
>   drivers/md/raid10.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 6c66357f92f5..4f8edb6ea3e2 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -1173,7 +1173,7 @@ static bool regular_request_wait(struct mddev *mddev, struct r10conf *conf,
>   }
>   
>   static void raid10_read_request(struct mddev *mddev, struct bio *bio,
> -				struct r10bio *r10_bio)
> +				struct r10bio *r10_bio, bool handle_error)
>   {
>   	struct r10conf *conf = mddev->private;
>   	struct bio *read_bio;
> @@ -1244,7 +1244,7 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
>   	}
>   	slot = r10_bio->read_slot;
>   
> -	if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
> +	if (!handle_error && blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
>   		r10_bio->start_time = bio_start_io_acct(bio);

I think a simpler way is just check R10BIO_ReadError here.

Thanks,
Guoqing

Re: [PATCH -next] raid10: fix leak of io accounting

[Yu Kuai]

Hi,

在 2023/03/09 14:36, Guoqing Jiang 写道:
> Hi,
> 
> What do you mean 'leak' here?

I try to mean that inflight counting is leaked, because it's increased
twice for one io.
> 
> On 3/4/23 15:01, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> handle_read_error() will resumit r10_bio by raid10_read_request(), which
>> will call bio_start_io_acct() again, while bio_end_io_acct() will only
>> be called once.
>>
>> Fix the problem by don't account io again from handle_read_error().
> 
> My understanding is it caused inaccurate io stats for bio which had a read
> error.
> 
>> Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>> ---
>>   drivers/md/raid10.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
>> index 6c66357f92f5..4f8edb6ea3e2 100644
>> --- a/drivers/md/raid10.c
>> +++ b/drivers/md/raid10.c
>> @@ -1173,7 +1173,7 @@ static bool regular_request_wait(struct mddev 
>> *mddev, struct r10conf *conf,
>>   }
>>   static void raid10_read_request(struct mddev *mddev, struct bio *bio,
>> -                struct r10bio *r10_bio)
>> +                struct r10bio *r10_bio, bool handle_error)
>>   {
>>       struct r10conf *conf = mddev->private;
>>       struct bio *read_bio;
>> @@ -1244,7 +1244,7 @@ static void raid10_read_request(struct mddev 
>> *mddev, struct bio *bio,
>>       }
>>       slot = r10_bio->read_slot;
>> -    if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
>> +    if (!handle_error && 
>> blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
>>           r10_bio->start_time = bio_start_io_acct(bio);
> 
> I think a simpler way is just check R10BIO_ReadError here.

No, I'm afraid this is incorrect because handle_read_error clears the
state before resubmiting the r10bio.

Thanks,
Kuai
> 
> Thanks,
> Guoqing
> .
> 

Re: [PATCH -next] raid10: fix leak of io accounting

[Guoqing Jiang]

On 3/9/23 14:56, Yu Kuai wrote:
> Hi,
>
> 在 2023/03/09 14:36, Guoqing Jiang 写道:
>> Hi,
>>
>> What do you mean 'leak' here?
>
> I try to mean that inflight counting is leaked, because it's increased
> twice for one io.

How about change the subject to something like?

'md/raid10: Don't call bio_start_io_acct twice for bio which experienced 
read error'

>
>>
>> On 3/4/23 15:01, Yu Kuai wrote:
>>> From: Yu Kuai <yukuai3@huawei.com>
>>>
>>> handle_read_error() will resumit r10_bio by raid10_read_request(), 
>>> which
>>> will call bio_start_io_acct() again, while bio_end_io_acct() will only
>>> be called once.
>>>
>>> Fix the problem by don't account io again from handle_read_error().
>>
>> My understanding is it caused inaccurate io stats for bio which had a 
>> read
>> error.
>>
>>> Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
>>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>>> ---
>>>   drivers/md/raid10.c | 8 ++++----
>>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
>>> index 6c66357f92f5..4f8edb6ea3e2 100644
>>> --- a/drivers/md/raid10.c
>>> +++ b/drivers/md/raid10.c
>>> @@ -1173,7 +1173,7 @@ static bool regular_request_wait(struct mddev 
>>> *mddev, struct r10conf *conf,
>>>   }
>>>   static void raid10_read_request(struct mddev *mddev, struct bio *bio,
>>> -                struct r10bio *r10_bio)
>>> +                struct r10bio *r10_bio, bool handle_error)
>>>   {
>>>       struct r10conf *conf = mddev->private;
>>>       struct bio *read_bio;
>>> @@ -1244,7 +1244,7 @@ static void raid10_read_request(struct mddev 
>>> *mddev, struct bio *bio,
>>>       }
>>>       slot = r10_bio->read_slot;
>>> -    if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
>>> +    if (!handle_error && 
>>> blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
>>>           r10_bio->start_time = bio_start_io_acct(bio);
>>
>> I think a simpler way is just check R10BIO_ReadError here.
>
> No, I'm afraid this is incorrect because handle_read_error clears the
> state before resubmiting the r10bio.

Right,

Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>

Thanks,
Guoqing

Re: [PATCH -next] raid10: fix leak of io accounting

[Yu Kuai]

Hi,

在 2023/03/09 15:27, Guoqing Jiang 写道:
> 
> 
> On 3/9/23 14:56, Yu Kuai wrote:
>> Hi,
>>
>> 在 2023/03/09 14:36, Guoqing Jiang 写道:
>>> Hi,
>>>
>>> What do you mean 'leak' here?
>>
>> I try to mean that inflight counting is leaked, because it's increased
>> twice for one io.
> 
> How about change the subject to something like?
> 
> 'md/raid10: Don't call bio_start_io_acct twice for bio which experienced 
> read error'
> 
Of course, I'll change that in v2.

>>
>>>
>>> On 3/4/23 15:01, Yu Kuai wrote:
>>>> From: Yu Kuai <yukuai3@huawei.com>
>>>>
>>>> handle_read_error() will resumit r10_bio by raid10_read_request(), 
>>>> which
>>>> will call bio_start_io_acct() again, while bio_end_io_acct() will only
>>>> be called once.
>>>>
>>>> Fix the problem by don't account io again from handle_read_error().
>>>
>>> My understanding is it caused inaccurate io stats for bio which had a 
>>> read
>>> error.
>>>
>>>> Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
>>>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>>>> ---
>>>>   drivers/md/raid10.c | 8 ++++----
>>>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
>>>> index 6c66357f92f5..4f8edb6ea3e2 100644
>>>> --- a/drivers/md/raid10.c
>>>> +++ b/drivers/md/raid10.c
>>>> @@ -1173,7 +1173,7 @@ static bool regular_request_wait(struct mddev 
>>>> *mddev, struct r10conf *conf,
>>>>   }
>>>>   static void raid10_read_request(struct mddev *mddev, struct bio *bio,
>>>> -                struct r10bio *r10_bio)
>>>> +                struct r10bio *r10_bio, bool handle_error)
>>>>   {
>>>>       struct r10conf *conf = mddev->private;
>>>>       struct bio *read_bio;
>>>> @@ -1244,7 +1244,7 @@ static void raid10_read_request(struct mddev 
>>>> *mddev, struct bio *bio,
>>>>       }
>>>>       slot = r10_bio->read_slot;
>>>> -    if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
>>>> +    if (!handle_error && 
>>>> blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
>>>>           r10_bio->start_time = bio_start_io_acct(bio);
>>>
>>> I think a simpler way is just check R10BIO_ReadError here.
>>
>> No, I'm afraid this is incorrect because handle_read_error clears the
>> state before resubmiting the r10bio.
> 
> Right,
> 
> Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>

Thanks for the review.
Kuai
> 
> Thanks,
> Guoqing
> .
>