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Date: Sun, 19 Dec 2010 22:16:40 -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() 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@....edu>
---
fs/ext4/dir.c | 42 ++++++++++++++++++++++++------------------
fs/ext4/ext4.h | 3 ++-
fs/ext4/namei.c | 14 +++++++-------
3 files changed, 33 insertions(+), 26 deletions(-)
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 @@ 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
*/
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 17baecb..49f1cea 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1639,7 +1639,8 @@ extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *,
struct ext4_dir_entry_2 *,
struct buffer_head *, unsigned int);
#define ext4_check_dir_entry(dir, de, bh, offset) \
- __ext4_check_dir_entry(__func__, __LINE__, (dir), (de), (bh), (offset))
+ unlikely(__ext4_check_dir_entry(__func__, __LINE__, (dir), (de), \
+ (bh), (offset)))
extern int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
__u32 minor_hash,
struct ext4_dir_entry_2 *dirent);
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 2030864..e275464 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -581,9 +581,9 @@ static int htree_dirblock_to_tree(struct file *dir_file,
dir->i_sb->s_blocksize -
EXT4_DIR_REC_LEN(0));
for (; de < top; de = ext4_next_entry(de, dir->i_sb->s_blocksize)) {
- if (!ext4_check_dir_entry(dir, de, bh,
- (block<<EXT4_BLOCK_SIZE_BITS(dir->i_sb))
- +((char *)de - bh->b_data))) {
+ if (ext4_check_dir_entry(dir, de, bh,
+ (block<<EXT4_BLOCK_SIZE_BITS(dir->i_sb))
+ + ((char *)de - bh->b_data))) {
/* On error, skip the f_pos to the next block. */
dir_file->f_pos = (dir_file->f_pos |
(dir->i_sb->s_blocksize - 1)) + 1;
@@ -820,7 +820,7 @@ static inline int search_dirblock(struct buffer_head *bh,
if ((char *) de + namelen <= dlimit &&
ext4_match (namelen, name, de)) {
/* found a match - just to be sure, do a full check */
- if (!ext4_check_dir_entry(dir, de, bh, offset))
+ if (ext4_check_dir_entry(dir, de, bh, offset))
return -1;
*res_dir = de;
return 1;
@@ -1269,7 +1269,7 @@ static int add_dirent_to_buf(handle_t *handle, struct dentry *dentry,
de = (struct ext4_dir_entry_2 *)bh->b_data;
top = bh->b_data + blocksize - reclen;
while ((char *) de <= top) {
- if (!ext4_check_dir_entry(dir, de, bh, offset))
+ if (ext4_check_dir_entry(dir, de, bh, offset))
return -EIO;
if (ext4_match(namelen, name, de))
return -EEXIST;
@@ -1636,7 +1636,7 @@ static int ext4_delete_entry(handle_t *handle,
pde = NULL;
de = (struct ext4_dir_entry_2 *) bh->b_data;
while (i < bh->b_size) {
- if (!ext4_check_dir_entry(dir, de, bh, i))
+ if (ext4_check_dir_entry(dir, de, bh, i))
return -EIO;
if (de == de_del) {
BUFFER_TRACE(bh, "get_write_access");
@@ -1919,7 +1919,7 @@ static int empty_dir(struct inode *inode)
}
de = (struct ext4_dir_entry_2 *) bh->b_data;
}
- if (!ext4_check_dir_entry(inode, de, bh, offset)) {
+ if (ext4_check_dir_entry(inode, de, bh, offset)) {
de = (struct ext4_dir_entry_2 *)(bh->b_data +
sb->s_blocksize);
offset = (offset | (sb->s_blocksize - 1)) + 1;
--
1.7.3.1
--
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