On 4/18/21 10:49 PM, Changheun Lee wrote:
>>> @@ -167,6 +168,7 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto
>>> max_sectors = round_down(max_sectors,
>>> limits->logical_block_size >> SECTOR_SHIFT);
>>> limits->max_sectors = max_sectors;
>>> + limits->bio_max_bytes = max_sectors << SECTOR_SHIFT;
>>>
>>> q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9);
>>> }
>>
>> Can the new shift operation overflow? If so, how about using
>> check_shl_overflow()?
>
> Actually, overflow might be not heppen in case of physical device.
> But I modified as below. feedback about this.
>
> @@ -168,6 +169,9 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto
> limits->logical_block_size >> SECTOR_SHIFT);
> limits->max_sectors = max_sectors;
>
> + limits->bio_max_bytes = check_shl_overflow(max_sectors, SECTOR_SHIFT,
> + &limits->bio_max_bytes) ? UINT_MAX : max_sectors << SECTOR_SHIFT;
> +
> q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9);
> }
> EXPORT_SYMBOL(blk_queue_max_hw_sectors);
If no overflow occurs, check_shl_overflow() stores the result in the
memory location the third argument points at. So the above expression
can be simplified into the following:
if (check_shl_overflow(max_sectors, SECTOR_SHIFT, &limits->bio_max_bytes)) {
limits->bio_max_bytes = UINT_MAX;
}
>>> diff --git a/include/linux/bio.h b/include/linux/bio.h
>>> index d0246c92a6e8..e5add63da3af 100644
>>> --- a/include/linux/bio.h
>>> +++ b/include/linux/bio.h
>>> @@ -106,6 +106,8 @@ static inline void *bio_data(struct bio *bio)
>>> return NULL;
>>> }
>>>
>>> +extern unsigned int bio_max_size(struct bio *bio);
>>
>> You may want to define bio_max_size() as an inline function in bio.h
>> such that no additional function calls are introduced in the hot path.
>
> I tried, but it is not easy. because request_queue structure of blkdev.h
> should be referred in bio.h. I think it's not good to apply as a inline function.
Please don't worry about this. Inlining bio_max_size() is not a big
concern to me.
Thanks,
Bart.
