linux-kernel - [PATCH v2 1/7] exfat: remove call ilog2() from exfat

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Date:   Tue, 13 Dec 2022 02:36:52 +0000
From:   "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>
To:     "sj1557.seo@...sung.com" <sj1557.seo@...sung.com>,
        "linkinjeon@...nel.org" <linkinjeon@...nel.org>
CC:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Andy.Wu@...y.com" <Andy.Wu@...y.com>,
        "Wataru.Aoyama@...y.com" <Wataru.Aoyama@...y.com>
Subject: [PATCH v2 1/7] exfat: remove call ilog2() from exfat_readdir()

There is no need to call ilog2() for the conversions between
cluster and dentry in exfat_readdir(), because these conversions
can be replaced with EXFAT_DEN_TO_CLU()/EXFAT_CLU_TO_DEN().

Code refinement, no functional changes.

Signed-off-by: Yuezhang Mo <Yuezhang.Mo@...y.com>
Reviewed-by: Andy Wu <Andy.Wu@...y.com>
Reviewed-by: Aoyama Wataru <wataru.aoyama@...y.com>
---
 fs/exfat/dir.c      |  9 ++++-----
 fs/exfat/exfat_fs.h | 10 ++++++++--
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index c05493fc9124..397ea2d98848 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -61,7 +61,7 @@ static void exfat_get_uniname_from_ext_entry(struct super_block *sb,
 /* read a directory entry from the opened directory */
 static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_entry *dir_entry)
 {
-	int i, dentries_per_clu, dentries_per_clu_bits = 0, num_ext;
+	int i, dentries_per_clu, num_ext;
 	unsigned int type, clu_offset, max_dentries;
 	struct exfat_chain dir, clu;
 	struct exfat_uni_name uni_name;
@@ -83,11 +83,10 @@ static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_ent
 			EXFAT_B_TO_CLU(i_size_read(inode), sbi), ei->flags);
 
 	dentries_per_clu = sbi->dentries_per_clu;
-	dentries_per_clu_bits = ilog2(dentries_per_clu);
 	max_dentries = (unsigned int)min_t(u64, MAX_EXFAT_DENTRIES,
-					   (u64)sbi->num_clusters << dentries_per_clu_bits);
+				(u64)EXFAT_CLU_TO_DEN(sbi->num_clusters, sbi));
 
-	clu_offset = dentry >> dentries_per_clu_bits;
+	clu_offset = EXFAT_DEN_TO_CLU(dentry, sbi);
 	exfat_chain_dup(&clu, &dir);
 
 	if (clu.flags == ALLOC_NO_FAT_CHAIN) {
@@ -162,7 +161,7 @@ static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_ent
 			dir_entry->entry = dentry;
 			brelse(bh);
 
-			ei->hint_bmap.off = dentry >> dentries_per_clu_bits;
+			ei->hint_bmap.off = EXFAT_DEN_TO_CLU(dentry, sbi);
 			ei->hint_bmap.clu = clu.dir;
 
 			*cpos = EXFAT_DEN_TO_B(dentry + 1 + num_ext);
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 324acc57d029..37e8af8042aa 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -101,11 +101,17 @@ enum {
 /*
  * helpers for block size to dentry size conversion.
  */
-#define EXFAT_B_TO_DEN_IDX(b, sbi)	\
-	((b) << ((sbi)->cluster_size_bits - DENTRY_SIZE_BITS))
 #define EXFAT_B_TO_DEN(b)		((b) >> DENTRY_SIZE_BITS)
 #define EXFAT_DEN_TO_B(b)		((b) << DENTRY_SIZE_BITS)
 
+/*
+ * helpers for cluster size to dentry size conversion.
+ */
+#define EXFAT_CLU_TO_DEN(clu, sbi)	\
+	((clu) << ((sbi)->cluster_size_bits - DENTRY_SIZE_BITS))
+#define EXFAT_DEN_TO_CLU(dentry, sbi)	\
+	((dentry) >> ((sbi)->cluster_size_bits - DENTRY_SIZE_BITS))
+
 /*
  * helpers for fat entry.
  */
-- 
2.25.1