linux-kernel - [PATCH v2] ext4: move `ext4_count_free` to ext4.h so it can be easily inlined

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Message-Id: <20230424183141.2005976-1-goldstein.w.n@gmail.com>
Date:   Mon, 24 Apr 2023 13:31:41 -0500
From:   Noah Goldstein <goldstein.w.n@...il.com>
To:     linux-ext4@...r.kernel.org
Cc:     goldstein.w.n@...il.com, tytso@....edu, adilger.kernel@...ger.ca,
        linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [PATCH v2] ext4: move `ext4_count_free` to ext4.h so it can be easily inlined

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