linux-kernel - Re: [PATCH v3 1/2] bio: limit bio max size

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Date:   Wed, 27 Jan 2021 01:03:16 +0000
From:   Damien Le Moal <Damien.LeMoal@....com>
To:     Changheun Lee <nanich.lee@...sung.com>
CC:     Johannes Thumshirn <Johannes.Thumshirn@....com>,
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Subject: Re: [PATCH v3 1/2] bio: limit bio max size

On 2021/01/27 9:36, Changheun Lee wrote:
>>> +
>>>  /**
>>>   * bio_reset - reinitialize a bio
>>>   * @bio:	bio to reset
>>> @@ -877,7 +892,7 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
>>>  		struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
>>>  
>>>  		if (page_is_mergeable(bv, page, len, off, same_page)) {
>>> -			if (bio->bi_iter.bi_size > UINT_MAX - len) {
>>> +			if (bio->bi_iter.bi_size > bio_max_size(bio) - len) {
>>>  				*same_page = false;
>>>  				return false;
>>>  			}
>>> diff --git a/include/linux/bio.h b/include/linux/bio.h
>>> index 1edda614f7ce..cdb134ca7bf5 100644
>>> --- a/include/linux/bio.h
>>> +++ b/include/linux/bio.h
>>> @@ -100,6 +100,8 @@ static inline void *bio_data(struct bio *bio)
>>>  	return NULL;
>>>  }
>>>  
>>> +extern unsigned int bio_max_size(struct bio *);
>>
>> No need for extern.
> 
> It's just for compile warning in my test environment.
> I'll remove it too. But I think compile warning could be in the other
> .c file which includes bio.h. Is it OK?

Hmmm... not having extern should not generate a compilation warning. There are
tons of functions declared without extern in header files in the kernel. What
compiler are you using ?


-- 
Damien Le Moal
Western Digital Research