Re: [PATCH] btrfs: reduce size and overhead of extent_map_block_end()

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

在 2024/7/24 00:46, fdmanana@kernel.org 写道:
> From: Filipe Manana <fdmanana@suse.com>
>
> At extent_map_block_end() we are calling the inline functions
> extent_map_block_start() and extent_map_block_len() multiple times, which
> results in expanding their code multiple times, increasing the compiled
> code size and repeating the computations those functions do.
>
> Improve this by caching their results in local variables.
>
> The size of the module before this change:
>
>     $ size fs/btrfs/btrfs.ko
>        text	   data	    bss	    dec	    hex	filename
>     1755770	 163800	  16920	1936490	 1d8c6a	fs/btrfs/btrfs.ko
>
> And after this change:
>
>     $ size fs/btrfs/btrfs.ko
>        text	   data	    bss	    dec	    hex	filename
>     1755656	 163800	  16920	1936376	 1d8bf8	fs/btrfs/btrfs.ko
>
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

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

Thanks,
Qu

> ---
>   fs/btrfs/extent_map.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
> index f85f0172b58b..806a8954b3d5 100644
> --- a/fs/btrfs/extent_map.c
> +++ b/fs/btrfs/extent_map.c
> @@ -192,10 +192,13 @@ static inline u64 extent_map_block_len(const struct extent_map *em)
>
>   static inline u64 extent_map_block_end(const struct extent_map *em)
>   {
> -	if (extent_map_block_start(em) + extent_map_block_len(em) <
> -	    extent_map_block_start(em))
> +	const u64 block_start = extent_map_block_start(em);
> +	const u64 block_end = block_start + extent_map_block_len(em);
> +
> +	if (block_end < block_start)
>   		return (u64)-1;
> -	return extent_map_block_start(em) + extent_map_block_len(em);
> +
> +	return block_end;
>   }
>
>   static bool can_merge_extent_map(const struct extent_map *em)