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ext4: optimize ext4_check_dir_entry() with unlikely() annotations

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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>
This commit is contained in:
Theodore Ts'o
2010-12-19 22:07:02 -05:00
parent b17b35ec13
commit cad3f00763
3 changed files with 32 additions and 25 deletions
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40
fs/ext4/dir.c
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@@ -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
*/