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

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Date:   Wed, 27 Jan 2021 14:22:57 +0900
From:   Changheun Lee <nanich.lee@...sung.com>
To:     damien.lemoal@....com
Cc:     Johannes.Thumshirn@....com, asml.silence@...il.com,
        axboe@...nel.dk, jisoo2146.oh@...sung.com, junho89.kim@...sung.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        ming.lei@...hat.com, mj0123.lee@...sung.com,
        nanich.lee@...sung.com, osandov@...com, patchwork-bot@...nel.org,
        seunghwan.hyun@...sung.com, sookwan7.kim@...sung.com,
        tj@...nel.org, tom.leiming@...il.com, woosung2.lee@...sung.com,
        yt0928.kim@...sung.com
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 ?
> 

Compiler imformation is below.

CROSS_COMPILE: android/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/bin/aarch64-linux-android-
CC: android/prebuilts/clang/host/linux-x86/clang-r383902/bin/clang
CLANG_TRIPLE: android/prebuilts/clang/host/linux-x86/clang-r383902/bin/aarch64-linux-gnu-
CROSS_COMPILE_COMPAT: android/prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9/bin/arm-linux-androideabi-


> 
> -- 
> Damien Le Moal
> Western Digital Research
> 

---
Changheun Lee
Samsung Electronics