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Commit f702ba0f authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: Don't use 'struct dentry' for internal lookups 



This is a port of a patch from Linus which fixes a 200+ byte stack
usage problem in ext4_get_parent().

It's more efficient to pass down only the actual parts of the dentry
that matter: the parent inode and the name, instead of allocating a
struct dentry on the stack.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 914258bf

fs/ext4/namei.c

+33 −35
Original line number Diff line number Diff line
@@ -159,7 +159,7 @@ static void dx_set_count(struct dx_entry *entries, unsigned value); 
static void dx_set_limit(struct dx_entry *entries, unsigned value);

static unsigned dx_root_limit(struct inode *dir, unsigned infosize);

static unsigned dx_node_limit(struct inode *dir);

static struct dx_frame *dx_probe(struct dentry *dentry,

static struct dx_frame *dx_probe(const struct qstr *d_name,

				 struct inode *dir,

				 struct dx_hash_info *hinfo,

				 struct dx_frame *frame,
@@ -177,8 +177,10 @@ static int ext4_htree_next_block(struct inode *dir, __u32 hash, 
				 struct dx_frame *frame,

				 struct dx_frame *frames,

				 __u32 *start_hash);

static struct buffer_head * ext4_dx_find_entry(struct dentry *dentry,

		       struct ext4_dir_entry_2 **res_dir, int *err);

static struct buffer_head * ext4_dx_find_entry(struct inode *dir,

		const struct qstr *d_name,

		struct ext4_dir_entry_2 **res_dir,

		int *err);

static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,

			     struct inode *inode);
@@ -345,7 +347,7 @@ struct stats dx_show_entries(struct dx_hash_info *hinfo, struct inode *dir, 
 * back to userspace.

 */

static struct dx_frame *

dx_probe(struct dentry *dentry, struct inode *dir,

dx_probe(const struct qstr *d_name, struct inode *dir,

	 struct dx_hash_info *hinfo, struct dx_frame *frame_in, int *err)

{

	unsigned count, indirect;
@@ -356,8 +358,6 @@ dx_probe(struct dentry *dentry, struct inode *dir, 
	u32 hash;



	frame->bh = NULL;

	if (dentry)

		dir = dentry->d_parent->d_inode;

	if (!(bh = ext4_bread (NULL,dir, 0, 0, err)))

		goto fail;

	root = (struct dx_root *) bh->b_data;
@@ -373,8 +373,8 @@ dx_probe(struct dentry *dentry, struct inode *dir, 
	}

	hinfo->hash_version = root->info.hash_version;

	hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;

	if (dentry)

		ext4fs_dirhash(dentry->d_name.name, dentry->d_name.len, hinfo);

	if (d_name)

		ext4fs_dirhash(d_name->name, d_name->len, hinfo);

	hash = hinfo->hash;



	if (root->info.unused_flags & 1) {
@@ -649,7 +649,7 @@ int ext4_htree_fill_tree(struct file *dir_file, __u32 start_hash, 
	}

	hinfo.hash = start_hash;

	hinfo.minor_hash = 0;

	frame = dx_probe(NULL, dir_file->f_path.dentry->d_inode, &hinfo, frames, &err);

	frame = dx_probe(NULL, dir, &hinfo, frames, &err);

	if (!frame)

		return err;
@@ -805,15 +805,15 @@ static inline int ext4_match (int len, const char * const name, 
 */

static inline int search_dirblock(struct buffer_head *bh,

				  struct inode *dir,

				  struct dentry *dentry,

				  const struct qstr *d_name,

				  unsigned long offset,

				  struct ext4_dir_entry_2 ** res_dir)

{

	struct ext4_dir_entry_2 * de;

	char * dlimit;

	int de_len;

	const char *name = dentry->d_name.name;

	int namelen = dentry->d_name.len;

	const char *name = d_name->name;

	int namelen = d_name->len;



	de = (struct ext4_dir_entry_2 *) bh->b_data;

	dlimit = bh->b_data + dir->i_sb->s_blocksize;
@@ -852,7 +852,8 @@ static inline int search_dirblock(struct buffer_head *bh, 
 * The returned buffer_head has ->b_count elevated.  The caller is expected

 * to brelse() it when appropriate.

 */

static struct buffer_head * ext4_find_entry (struct dentry *dentry,

static struct buffer_head * ext4_find_entry (struct inode *dir,

					const struct qstr *d_name,

					struct ext4_dir_entry_2 ** res_dir)

{

	struct super_block *sb;
@@ -866,16 +867,15 @@ static struct buffer_head * ext4_find_entry (struct dentry *dentry, 
	int num = 0;

	ext4_lblk_t  nblocks;

	int i, err;

	struct inode *dir = dentry->d_parent->d_inode;

	int namelen;



	*res_dir = NULL;

	sb = dir->i_sb;

	namelen = dentry->d_name.len;

	namelen = d_name->len;

	if (namelen > EXT4_NAME_LEN)

		return NULL;

	if (is_dx(dir)) {

		bh = ext4_dx_find_entry(dentry, res_dir, &err);

		bh = ext4_dx_find_entry(dir, d_name, res_dir, &err);

		/*

		 * On success, or if the error was file not found,

		 * return.  Otherwise, fall back to doing a search the
@@ -928,7 +928,7 @@ restart: 
			brelse(bh);

			goto next;

		}

		i = search_dirblock(bh, dir, dentry,

		i = search_dirblock(bh, dir, d_name,

			    block << EXT4_BLOCK_SIZE_BITS(sb), res_dir);

		if (i == 1) {

			EXT4_I(dir)->i_dir_start_lookup = block;
@@ -962,7 +962,7 @@ cleanup_and_exit: 
	return ret;

}



static struct buffer_head * ext4_dx_find_entry(struct dentry *dentry,

static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct qstr *d_name,

		       struct ext4_dir_entry_2 **res_dir, int *err)

{

	struct super_block * sb;
@@ -973,14 +973,13 @@ static struct buffer_head * ext4_dx_find_entry(struct dentry *dentry, 
	struct buffer_head *bh;

	ext4_lblk_t block;

	int retval;

	int namelen = dentry->d_name.len;

	const u8 *name = dentry->d_name.name;

	struct inode *dir = dentry->d_parent->d_inode;

	int namelen = d_name->len;

	const u8 *name = d_name->name;



	sb = dir->i_sb;

	/* NFS may look up ".." - look at dx_root directory block */

	if (namelen > 2 || name[0] != '.'||(name[1] != '.' && name[1] != '\0')){

		if (!(frame = dx_probe(dentry, NULL, &hinfo, frames, err)))

		if (!(frame = dx_probe(d_name, dir, &hinfo, frames, err)))

			return NULL;

	} else {

		frame = frames;
@@ -1041,7 +1040,7 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, stru 
	if (dentry->d_name.len > EXT4_NAME_LEN)

		return ERR_PTR(-ENAMETOOLONG);



	bh = ext4_find_entry(dentry, &de);

	bh = ext4_find_entry(dir, &dentry->d_name, &de);

	inode = NULL;

	if (bh) {

		unsigned long ino = le32_to_cpu(de->inode);
@@ -1064,15 +1063,14 @@ struct dentry *ext4_get_parent(struct dentry *child) 
	unsigned long ino;

	struct dentry *parent;

	struct inode *inode;

	struct dentry dotdot;

	static const struct qstr dotdot = {

		.name = "..",

		.len = 2,

	};

	struct ext4_dir_entry_2 * de;

	struct buffer_head *bh;



	dotdot.d_name.name = "..";

	dotdot.d_name.len = 2;

	dotdot.d_parent = child; /* confusing, isn't it! */



	bh = ext4_find_entry(&dotdot, &de);

	bh = ext4_find_entry(child->d_inode, &dotdot, &de);

	inode = NULL;

	if (!bh)

		return ERR_PTR(-ENOENT);
@@ -1508,7 +1506,7 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry, 
	struct ext4_dir_entry_2 *de;

	int err;



	frame = dx_probe(dentry, NULL, &hinfo, frames, &err);

	frame = dx_probe(&dentry->d_name, dir, &hinfo, frames, &err);

	if (!frame)

		return err;

	entries = frame->entries;
@@ -2089,7 +2087,7 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry) 
		return PTR_ERR(handle);



	retval = -ENOENT;

	bh = ext4_find_entry(dentry, &de);

	bh = ext4_find_entry(dir, &dentry->d_name, &de);

	if (!bh)

		goto end_rmdir;
@@ -2151,7 +2149,7 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry) 
		handle->h_sync = 1;



	retval = -ENOENT;

	bh = ext4_find_entry(dentry, &de);

	bh = ext4_find_entry(dir, &dentry->d_name, &de);

	if (!bh)

		goto end_unlink;
@@ -2312,7 +2310,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, 
	if (IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir))

		handle->h_sync = 1;



	old_bh = ext4_find_entry(old_dentry, &old_de);

	old_bh = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de);

	/*

	 *  Check for inode number is _not_ due to possible IO errors.

	 *  We might rmdir the source, keep it as pwd of some process
@@ -2325,7 +2323,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, 
		goto end_rename;



	new_inode = new_dentry->d_inode;

	new_bh = ext4_find_entry(new_dentry, &new_de);

	new_bh = ext4_find_entry(new_dir, &new_dentry->d_name, &new_de);

	if (new_bh) {

		if (!new_inode) {

			brelse(new_bh);
@@ -2392,7 +2390,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, 
		struct buffer_head *old_bh2;

		struct ext4_dir_entry_2 *old_de2;



		old_bh2 = ext4_find_entry(old_dentry, &old_de2);

		old_bh2 = ext4_find_entry(old_dir, &old_dentry->d_name, &old_de2);

		if (old_bh2) {

			retval = ext4_delete_entry(handle, old_dir,

						   old_de2, old_bh2);