linux-kernel - Re: [PATCH] btrfs: Fix csum_tree_block to avoid tripping on -Werror=array-bounds

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Message-ID: <20230529134423.GE575@twin.jikos.cz>
Date:   Mon, 29 May 2023 15:44:23 +0200
From:   David Sterba <dsterba@...e.cz>
To:     pengfuyuan <pengfuyuan@...inos.cn>
Cc:     dsterba@...e.cz, Qu Wenruo <quwenruo.btrfs@....com>,
        Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs: Fix csum_tree_block to avoid tripping on
 -Werror=array-bounds

On Mon, May 29, 2023 at 11:28:59AM +0800, pengfuyuan wrote:
> 
> On 2023/5/26 22:35, David Sterba wrote:
> > On Tue, May 23, 2023 at 09:32:12PM +0200, David Sterba wrote:
> >> On Tue, May 23, 2023 at 03:33:22PM +0800, Qu Wenruo wrote:
> >>> On 2023/5/23 15:09, pengfuyuan wrote:
> >>> Although even with such change, I'm still not sure if it's any better or
> >>> worse, as most of the calculation can still be bulky.
> > The final version is
> >
> > 	for (i = 1; i < num_pages && INLINE_EXTENT_BUFFER_PAGES > 1; i++)
> >
> > ie. 'INLINE_EXTENT_BUFFER_PAGES > 1' can be evaluated at compile time
> > and result in removing the for loop completely.
> >
> > Pengfuyuan, can you please do a build test that it does not report the
> > warning anymore? The diff is:
> >
> > --- a/fs/btrfs/disk-io.c
> > +++ b/fs/btrfs/disk-io.c
> > @@ -88,7 +88,6 @@ static void csum_tree_block(struct extent_buffer *buf, u8 *result)
> >          const int first_page_part = min_t(u32, PAGE_SIZE, fs_info->nodesize);
> >          SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
> >          char *kaddr;
> > -       int i;
> >   
> >          shash->tfm = fs_info->csum_shash;
> >          crypto_shash_init(shash);
> > @@ -96,7 +95,7 @@ static void csum_tree_block(struct extent_buffer *buf, u8 *result)
> >          crypto_shash_update(shash, kaddr + BTRFS_CSUM_SIZE,
> >                              first_page_part - BTRFS_CSUM_SIZE);
> >   
> > -       for (i = 1; i < num_pages; i++) {
> > +       for (int i = 1; i < num_pages && INLINE_EXTENT_BUFFER_PAGES > 1; i++) {
> >                  kaddr = page_address(buf->pages[i]);
> >                  crypto_shash_update(shash, kaddr, PAGE_SIZE);
> >          }
> > ---
> 
> I did a build test on the mips64 architecture, the compilation passed, 
> and it no longer reported warnings.

Thanks, patch added to misc-next.