Re: [PATCH V3] block: no show partitions if partno corrupted

[Edward Adam Davis <eadavis@qq.com>]

On Tue, 14 Jan 2025 08:25:13 -0700, Jens Axboe wrote:
>> On Tue, 14 Jan 2025 08:02:15 -0700, Jens Axboe wrote:
>>>> diff --git a/block/genhd.c b/block/genhd.c
>>>> index 9130e163e191..3a9c36ad6bbd 100644
>>>> --- a/block/genhd.c
>>>> +++ b/block/genhd.c
>>>> @@ -890,6 +890,9 @@ static int show_partition(struct seq_file *seqf, void *v)
>>>>
>>>>  	rcu_read_lock();
>>>>  	xa_for_each(&sgp->part_tbl, idx, part) {
>>>> +		int partno = bdev_partno(part);
>>>> +
>>>> +		WARN_ON_ONCE(partno >= DISK_MAX_PARTS);
>>>>  		if (!bdev_nr_sectors(part))
>>>>  			continue;
>>>>  		seq_printf(seqf, "%4d  %7d %10llu %pg\n",
>>>
>>> Surely you still want to continue for that condition?
>> No.
>
>No?
>
>> But like following, ok?
>> diff --git a/block/genhd.c b/block/genhd.c
>> index 9130e163e191..142b13620f0c 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -890,7 +890,10 @@ static int show_partition(struct seq_file *seqf, void *v)
>>
>>         rcu_read_lock();
>>         xa_for_each(&sgp->part_tbl, idx, part) {
>> -               if (!bdev_nr_sectors(part))
>> +               int partno = bdev_partno(part);
>> +
>> +               WARN_ON_ONCE(partno >= DISK_MAX_PARTS);
>> +               if (!bdev_nr_sectors(part) || partno >= DISK_MAX_PARTS)
>>                         continue;
>>                 seq_printf(seqf, "%4d  %7d %10llu %pg\n",
>>                            MAJOR(part->bd_dev), MINOR(part->bd_dev),
>
>That's just silly...
I checked WARN_ON_ONCE(), and when the condition is met, the subsequent
WARN_ON_ONCE() will still return true, so adding it will not affect the
judgment of the condition.
It just issues a warning the first time the condition is met, and it will
still return true if the condition is true.
>
>	xa_for_each(&sgp->part_tbl, idx, part) {
>		int partno = bdev_partno(part);
>
>		if (!bdev_nr_sectors(part))
>			continue;
>		if (WARN_ON_ONCE(partno >= DISK_MAX_PARTS))
>			continue;
>
>		...
>	}

Edward