Re: [PATCH 13/21] ext4: remove dead check in mb_buddy_mark_free

[Ojaswin Mujoo]

On Fri, Feb 10, 2023 at 03:48:17AM +0800, Kemeng Shi wrote:
> We always adjust first to even number and adjust last to odd number, so
> first == last will never happen. Remove this dead check.
> 
> Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
> ---
>  fs/ext4/mballoc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index bdabe0d81d4a..0fdbf16ac180 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -1718,7 +1718,8 @@ static void mb_buddy_mark_free(struct ext4_buddy *e4b, int first, int last)
>  			break;
>  		order++;
>  
> -		if (first == last || !(buddy2 = mb_find_buddy(e4b, order, &max))) {
> +		buddy2 = mb_find_buddy(e4b, order, &max);
> +		if (!buddy2) {
>  			mb_clear_bits(buddy, first, last - first + 1);
>  			e4b->bd_info->bb_counters[order - 1] += last - first + 1;
>  			break;
> -- 
> 2.30.0
> 
Okay, so I checked the code and seems like you are right. There is can't be any
scenario where (first == last) after the calls to mb_buddy_adjust_border().

However, I'm a bit hesitant to give my Reviewed by since buddy algo is still a
bit confusing to me and I might be missing some weird edge case.  Maybe someone
can help double check this.