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>
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index ece76fb..bd5d74d 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -60,7 +60,11 @@
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 @@
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 @@
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
*/