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[PATCH v2 3/9] block: WARN if bdev inflight counter is negative

Yu Kuai posted 9 patches 7 months, 3 weeks ago
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[PATCH v2 3/9] block: WARN if bdev inflight counter is negative
Posted by Yu Kuai 7 months, 3 weeks ago 
From: Yu Kuai <yukuai3@huawei.com>

Which means there is a BUG for related bio-based disk driver, or blk-mq
for rq-based disk, it's better not to hide the BUG.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 block/genhd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index f671d9ee00c4..d158c25237b6 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -136,9 +136,9 @@ static void part_in_flight_rw(struct block_device *part,
 		inflight[0] += part_stat_local_read_cpu(part, in_flight[0], cpu);
 		inflight[1] += part_stat_local_read_cpu(part, in_flight[1], cpu);
 	}
-	if ((int)inflight[0] < 0)
+	if (WARN_ON_ONCE((int)inflight[0] < 0))
 		inflight[0] = 0;
-	if ((int)inflight[1] < 0)
+	if (WARN_ON_ONCE((int)inflight[1] < 0))
 		inflight[1] = 0;
 }
 
-- 
2.39.2
Re: [PATCH v2 3/9] block: WARN if bdev inflight counter is negative
Posted by Hannes Reinecke 7 months, 3 weeks ago 
On 4/27/25 10:29, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> Which means there is a BUG for related bio-based disk driver, or blk-mq
> for rq-based disk, it's better not to hide the BUG.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
>   block/genhd.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
Please make 'BUG' lowercase.

Otherwise:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
Re: [PATCH v2 3/9] block: WARN if bdev inflight counter is negative
Posted by John Garry 7 months, 3 weeks ago 
On 27/04/2025 09:29, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> Which means there is a BUG

nit: to me, BUG means symbol BUG(), and not a software bug (which I 
think that you mean)

> for related bio-based disk driver, or blk-mq
> for rq-based disk, it's better not to hide the BUG.

AFICS, this check was not present for mq, so is it really required now? 
I suppose that the code is simpler to always have the check. I find it 
an odd check to begin with...

> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
>   block/genhd.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index f671d9ee00c4..d158c25237b6 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -136,9 +136,9 @@ static void part_in_flight_rw(struct block_device *part,
>   		inflight[0] += part_stat_local_read_cpu(part, in_flight[0], cpu);
>   		inflight[1] += part_stat_local_read_cpu(part, in_flight[1], cpu);
>   	}
> -	if ((int)inflight[0] < 0)
> +	if (WARN_ON_ONCE((int)inflight[0] < 0))
>   		inflight[0] = 0;
> -	if ((int)inflight[1] < 0)
> +	if (WARN_ON_ONCE((int)inflight[1] < 0))
>   		inflight[1] = 0;
>   }
>
Re: [PATCH v2 3/9] block: WARN if bdev inflight counter is negative
Posted by Yu Kuai 7 months, 3 weeks ago 
Hi,

在 2025/04/28 22:06, John Garry 写道:
> On 27/04/2025 09:29, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> Which means there is a BUG
> 
> nit: to me, BUG means symbol BUG(), and not a software bug (which I 
> think that you mean)

Actually, I mean the bio-based disk driver or blk-mq messed up the IO
accounting, IO done is more than IO start, and this is a bug.
> 
>> for related bio-based disk driver, or blk-mq
>> for rq-based disk, it's better not to hide the BUG.
> 
> AFICS, this check was not present for mq, so is it really required now? 
> I suppose that the code is simpler to always have the check. I find it 
> an odd check to begin with...

This check do present for mq, for example, diskstats_show() and
update_io_ticks().

Thanks,
Kuai

> 
>>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>> ---
>>   block/genhd.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/genhd.c b/block/genhd.c
>> index f671d9ee00c4..d158c25237b6 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -136,9 +136,9 @@ static void part_in_flight_rw(struct block_device 
>> *part,
>>           inflight[0] += part_stat_local_read_cpu(part, in_flight[0], 
>> cpu);
>>           inflight[1] += part_stat_local_read_cpu(part, in_flight[1], 
>> cpu);
>>       }
>> -    if ((int)inflight[0] < 0)
>> +    if (WARN_ON_ONCE((int)inflight[0] < 0))
>>           inflight[0] = 0;
>> -    if ((int)inflight[1] < 0)
>> +    if (WARN_ON_ONCE((int)inflight[1] < 0))
>>           inflight[1] = 0;
>>   }
> 
> 
> .
>
Re: [PATCH v2 3/9] block: WARN if bdev inflight counter is negative
Posted by John Garry 7 months, 3 weeks ago 
On 29/04/2025 02:43, Yu Kuai wrote:
> accounting, IO done is more than IO start, and this is a bug.
>>
>>> for related bio-based disk driver, or blk-mq
>>> for rq-based disk, it's better not to hide the BUG.
>>
>> AFICS, this check was not present for mq, so is it really required 
>> now? I suppose that the code is simpler to always have the check. I 
>> find it an odd check to begin with...
> 
> This check do present for mq, for example, diskstats_show() and
> update_io_ticks().

ok, I just noticed this in part_inflight_show() -> 
blk_mq_in_flight_rw(), which didn't have such a check. I think that is 
because we expect the tagset iter to provide a sane count value.

Thanks,
John
Re: [PATCH v2 3/9] block: WARN if bdev inflight counter is negative
Posted by Christoph Hellwig 7 months, 3 weeks ago 
Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Patchew 2.1-devel-b67e4c2

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