ext4: optimize ext4_check_dir_entry() with unlikely() annotations

This function gets called a lot for large directories, and the answer
is almost always "no, no, there's no problem".  This means using
unlikely() is a good thing.

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

1 files changed, 23 insertions, 17 deletions

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index ece76fb6a40c..bd5d74d06399 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -60,7 +60,11 @@ static unsigned char get_dtype(struct super_block *sb, int filetype)
         return (ext4_filetype_table[filetype]);
 }
 
-
+/*
+ * Return 0 if the directory entry is OK, and 1 if there is a problem
+ *
+ * Note: this is the opposite of what ext2 and ext3 historically returned...
+ */
 int __ext4_check_dir_entry(const char *function, unsigned int line,
                            struct inode *dir,
                            struct ext4_dir_entry_2 *de,
@@ -71,26 +75,28 @@ int __ext4_check_dir_entry(const char *function, unsigned int line,
         const int rlen = ext4_rec_len_from_disk(de->rec_len,
                                                 dir->i_sb->s_blocksize);
 
-        if (rlen < EXT4_DIR_REC_LEN(1))
+        if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
                 error_msg = "rec_len is smaller than minimal";
-        else if (rlen % 4 != 0)
+        else if (unlikely(rlen % 4 != 0))
                 error_msg = "rec_len % 4 != 0";
-        else if (rlen < EXT4_DIR_REC_LEN(de->name_len))
+        else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
                 error_msg = "rec_len is too small for name_len";
-        else if (((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)
+        else if (unlikely(((char *) de - bh->b_data) + rlen >
+                          dir->i_sb->s_blocksize))
                 error_msg = "directory entry across blocks";
-        else if (le32_to_cpu(de->inode) >
-                        le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count))
+        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";
+        else
+                return 0;
 
-        if (error_msg != NULL)
-                ext4_error_inode(dir, function, line, bh->b_blocknr,
-                        "bad entry in directory: %s - "
-                        "offset=%u(%u), inode=%u, rec_len=%d, name_len=%d",
-                        error_msg, (unsigned) (offset%bh->b_size), offset,
-                        le32_to_cpu(de->inode),
-                        rlen, de->name_len);
-        return error_msg == NULL ? 1 : 0;
+        ext4_error_inode(dir, function, line, bh->b_blocknr,
+                         "bad entry in directory: %s - "
+                         "offset=%u(%u), inode=%u, rec_len=%d, name_len=%d",
+                         error_msg, (unsigned) (offset%bh->b_size), offset,
+                         le32_to_cpu(de->inode),
+                         rlen, de->name_len);
+        return 1;
 }
 
 static int ext4_readdir(struct file *filp,
@@ -194,8 +200,8 @@ revalidate:
                 while (!error && filp->f_pos < inode->i_size
                        && offset < sb->s_blocksize) {
                         de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
-                        if (!ext4_check_dir_entry(inode, de,
-                                                  bh, offset)) {
+                        if (ext4_check_dir_entry(inode, de,
+                                                 bh, offset)) {
                                 /*
                                  * On error, skip the f_pos to the next block
                                  */