linux-kernel - Re: [PATCH v1] ext4: move `ext4_count_free` to ext4.h so it can be easily inlined

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Message-ID: <20230424162413.hiimozuw44fhht4a@quack3>
Date:   Mon, 24 Apr 2023 18:24:13 +0200
From:   Jan Kara <jack@...e.cz>
To:     Noah Goldstein <goldstein.w.n@...il.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] ext4: move `ext4_count_free` to ext4.h so it can be
 easily inlined

On Thu 20-04-23 20:47:49, Noah Goldstein wrote:
> `ext4_count_free` is a one-line helper that is clearly better off
> being inlined. This saves a handful instructions in `vmlinux` on x86.
> 
> Instruction estimates use `wc -l` on `objdump`
> Before: 8539271
> After : 8539248
> 
> So saves roughly 20 instructions
> 
> Signed-off-by: Noah Goldstein <goldstein.w.n@...il.com>

Looks fine. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/bitmap.c | 5 -----
>  fs/ext4/ext4.h   | 6 +++++-
>  2 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ext4/bitmap.c b/fs/ext4/bitmap.c
> index f63e028c638c..c3cd2b878bbd 100644
> --- a/fs/ext4/bitmap.c
> +++ b/fs/ext4/bitmap.c
> @@ -11,11 +11,6 @@
>  #include <linux/buffer_head.h>
>  #include "ext4.h"
>  
> -unsigned int ext4_count_free(char *bitmap, unsigned int numchars)
> -{
> -	return numchars * BITS_PER_BYTE - memweight(bitmap, numchars);
> -}
> -
>  int ext4_inode_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,
>  				  struct ext4_group_desc *gdp,
>  				  struct buffer_head *bh, int sz)
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 08b29c289da4..6e1d3c175a70 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -2675,7 +2675,11 @@ struct mmpd_data {
>  # define NORET_AND	noreturn,
>  
>  /* bitmap.c */
> -extern unsigned int ext4_count_free(char *bitmap, unsigned numchars);
> +static inline unsigned int ext4_count_free(char *bitmap, unsigned int numchars)
> +{
> +	return numchars * BITS_PER_BYTE - memweight(bitmap, numchars);
> +}
> +
>  void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
>  				struct ext4_group_desc *gdp,
>  				struct buffer_head *bh, int sz);
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR