Re: [PATCH 9/9] btrfs: clean up header members offsets in write helpers

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2021/5/26 上午1:08, David Sterba wrote:
> Move header offsetof() to the expression that calculates the address so
> it's part of get_eb_offset_in_page where the 2nd parameter is the member
> offset.
>
> Signed-off-by: David Sterba <dsterba@suse.com>

Indeed better than the original expression.

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu
> ---
>   fs/btrfs/extent_io.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 2b250c610562..2e924f60ea6f 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -6519,9 +6519,10 @@ void write_extent_buffer_chunk_tree_uuid(const struct extent_buffer *eb,
>   	char *kaddr;
>
>   	assert_eb_page_uptodate(eb, eb->pages[0]);
> -	kaddr = page_address(eb->pages[0]) + get_eb_offset_in_page(eb, 0);
> -	memcpy(kaddr + offsetof(struct btrfs_header, chunk_tree_uuid), srcv,
> -			BTRFS_FSID_SIZE);
> +	kaddr = page_address(eb->pages[0]) +
> +		get_eb_offset_in_page(eb, offsetof(struct btrfs_header,
> +						   chunk_tree_uuid));
> +	memcpy(kaddr, srcv, BTRFS_FSID_SIZE);
>   }
>
>   void write_extent_buffer_fsid(const struct extent_buffer *eb, const void *srcv)
> @@ -6529,9 +6530,9 @@ void write_extent_buffer_fsid(const struct extent_buffer *eb, const void *srcv)
>   	char *kaddr;
>
>   	assert_eb_page_uptodate(eb, eb->pages[0]);
> -	kaddr = page_address(eb->pages[0]) + get_eb_offset_in_page(eb, 0);
> -	memcpy(kaddr + offsetof(struct btrfs_header, fsid), srcv,
> -			BTRFS_FSID_SIZE);
> +	kaddr = page_address(eb->pages[0]) +
> +		get_eb_offset_in_page(eb, offsetof(struct btrfs_header, fsid));
> +	memcpy(kaddr, srcv, BTRFS_FSID_SIZE);
>   }
>
>   void write_extent_buffer(const struct extent_buffer *eb, const void *srcv,
>