linux-ext4 - [PATCH] ext4: optimize __ext4_check_dir

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Message-Id: <20191209004346.38526-1-tytso@mit.edu>
Date:   Sun,  8 Dec 2019 19:43:46 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:     "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH] ext4: optimize __ext4_check_dir_entry()

Make __ext4_check_dir_entry() a bit easier to understand, and reduce
the object size of the function by over 11%.

Signed-off-by: Theodore Ts'o <tytso@....edu>
---

As a follow-up to "ext4: check for directory entries too close to block end"

 fs/ext4/dir.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 6305d5ec25af..9f00fc0bf21d 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -72,6 +72,7 @@ int __ext4_check_dir_entry(const char *function, unsigned int line,
 	const char *error_msg = NULL;
 	const int rlen = ext4_rec_len_from_disk(de->rec_len,
 						dir->i_sb->s_blocksize);
+	const int next_offset = ((char *) de - buf) + rlen;
 
 	if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
 		error_msg = "rec_len is smaller than minimal";
@@ -79,13 +80,11 @@ int __ext4_check_dir_entry(const char *function, unsigned int line,
 		error_msg = "rec_len % 4 != 0";
 	else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
 		error_msg = "rec_len is too small for name_len";
-	else if (unlikely(((char *) de - buf) + rlen > size))
+	else if (unlikely(next_offset > size))
 		error_msg = "directory entry overrun";
-	else if (unlikely(((char *) de - buf) + rlen >
-			  size - EXT4_DIR_REC_LEN(1) &&
-			  ((char *) de - buf) + rlen != size)) {
+	else if (unlikely(next_offset > size - EXT4_DIR_REC_LEN(1) &&
+			  next_offset != size))
 		error_msg = "directory entry too close to block end";
-	}
 	else if (unlikely(le32_to_cpu(de->inode) >
 			le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
 		error_msg = "inode out of bounds";
-- 
2.23.0