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

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Date:   Mon, 24 Apr 2023 13:32:20 -0500
From:   Noah Goldstein <goldstein.w.n@...il.com>
To:     Jan Kara <jack@...e.cz>
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 Mon, Apr 24, 2023 at 11:24 AM Jan Kara <jack@...e.cz> wrote:
>
> 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>
>
Done, thank you.

>                                                                 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