Re: [dm-devel] [PATCH v2 07/10] block: use sectors_to_npage() and PAGE_SECTORS to clean up code

[Leizhen (ThunderTown)]

On 2020/5/15 12:19, Matthew Wilcox wrote:
> On Thu, May 07, 2020 at 03:50:57PM +0800, Zhen Lei wrote:
>> +++ b/block/blk-settings.c
>> @@ -150,7 +150,7 @@ void blk_queue_max_hw_sectors(struct request_queue *q, 
>> unsigned int max_hw_secto
>>      unsigned int max_sectors;
>>  
>>      if ((max_hw_sectors << 9) < PAGE_SIZE) {
>> -            max_hw_sectors = 1 << (PAGE_SHIFT - 9);
>> +            max_hw_sectors = PAGE_SECTORS;
> 
> Surely this should be:
> 
>       if (max_hw_sectors < PAGE_SECTORS) {
>               max_hw_sectors = PAGE_SECTORS;
> 
> ... no?

I've noticed this place before. "(max_hw_sectors << 9) < PAGE_SIZE" can also 
make sure
that max_hw_sectors is not too large, that means (max_hw_sectors << 9) may 
overflow.

> 
>> -    page = read_mapping_page(mapping,
>> -                    (pgoff_t)(n >> (PAGE_SHIFT - 9)), NULL);
>> +    page = read_mapping_page(mapping, (pgoff_t)sectors_to_npage(n), NULL);
> 
> ... again, get the type right, and you won't need the cast.
OK, I'll consider it.

> 
> 
> .
> 

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