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

[pengfuyuan]

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.
> > Yeah I think the calculations would have to be conditional or keeping
> > some state. I'd like to keep the structure of the first page and the
> > rest.
> >
> > Possible ways is to add extra condition
> >
> > 	for (i = 1; i < num_pages && i < INLINE_EXTENT_BUFFER_PAGES; i++)
> 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.

Thank you very much and wish you a happy life.


Thanks.