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Commit cad3f007 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

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: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent b17b35ec

fs/ext4/dir.c

+23 −17
Original line number Diff line number Diff line
@@ -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;

	return 1;

}



static int ext4_readdir(struct file *filp,
@@ -194,7 +200,7 @@ static int ext4_readdir(struct file *filp, 
		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,

			if (ext4_check_dir_entry(inode, de,

						 bh, offset)) {

				/*

				 * On error, skip the f_pos to the next block

fs/ext4/ext4.h

+2 −1
Original line number Diff line number Diff line
@@ -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);

fs/ext4/namei.c

+7 −7
Original line number Diff line number Diff line
@@ -581,7 +581,7 @@ 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,

		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. */
@@ -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;