Commit 0c73f18b authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
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sysfs: use singly-linked list for sysfs_dirent tree 



Make sysfs_dirent use singly linked list for its tree structure.
sysfs_link_sibling() and sysfs_unlink_sibling() functions are added to
handle simpler cases.  It adds some complexity and cpu cycle overhead
but reduced memory footprint is worthwhile on big machines.

This change reduces the sizeof sysfs_dirent from 104 to 88 on 64bit
and from 60 to 52 on 32bit.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 8619f979

fs/sysfs/dir.c

+102 −44
Original line number Diff line number Diff line
@@ -21,6 +21,48 @@ spinlock_t kobj_sysfs_assoc_lock = SPIN_LOCK_UNLOCKED; 
static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED;

static DEFINE_IDA(sysfs_ino_ida);



/**

 *	sysfs_link_sibling - link sysfs_dirent into sibling list

 *	@sd: sysfs_dirent of interest

 *

 *	Link @sd into its sibling list which starts from

 *	sd->s_parent->s_children.

 *

 *	Locking:

 *	mutex_lock(sd->s_parent->dentry->d_inode->i_mutex)

 */

static void sysfs_link_sibling(struct sysfs_dirent *sd)

{

	struct sysfs_dirent *parent_sd = sd->s_parent;



	BUG_ON(sd->s_sibling);

	sd->s_sibling = parent_sd->s_children;

	parent_sd->s_children = sd;

}



/**

 *	sysfs_unlink_sibling - unlink sysfs_dirent from sibling list

 *	@sd: sysfs_dirent of interest

 *

 *	Unlink @sd from its sibling list which starts from

 *	sd->s_parent->s_children.

 *

 *	Locking:

 *	mutex_lock(sd->s_parent->dentry->d_inode->i_mutex)

 */

static void sysfs_unlink_sibling(struct sysfs_dirent *sd)

{

	struct sysfs_dirent **pos;



	for (pos = &sd->s_parent->s_children; *pos; pos = &(*pos)->s_sibling) {

		if (*pos == sd) {

			*pos = sd->s_sibling;

			sd->s_sibling = NULL;

			break;

		}

	}

}



/**

 *	sysfs_get_active - get an active reference to sysfs_dirent

 *	@sd: sysfs_dirent to get an active reference to
@@ -73,9 +115,9 @@ void sysfs_put_active(struct sysfs_dirent *sd) 
		return;



	/* atomic_dec_return() is a mb(), we'll always see the updated

	 * sd->s_sibling.next.

	 * sd->s_sibling.

	 */

	cmpl = (void *)sd->s_sibling.next;

	cmpl = (void *)sd->s_sibling;

	complete(cmpl);

}
@@ -129,18 +171,18 @@ void sysfs_deactivate(struct sysfs_dirent *sd) 
	DECLARE_COMPLETION_ONSTACK(wait);

	int v;



	BUG_ON(!list_empty(&sd->s_sibling));

	sd->s_sibling.next = (void *)&wait;

	BUG_ON(sd->s_sibling);

	sd->s_sibling = (void *)&wait;



	/* atomic_add_return() is a mb(), put_active() will always see

	 * the updated sd->s_sibling.next.

	 * the updated sd->s_sibling.

	 */

	v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active);



	if (v != SD_DEACTIVATED_BIAS)

		wait_for_completion(&wait);



	INIT_LIST_HEAD(&sd->s_sibling);

	sd->s_sibling = NULL;

}



static int sysfs_alloc_ino(ino_t *pino)
@@ -237,8 +279,6 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type) 
	atomic_set(&sd->s_count, 1);

	atomic_set(&sd->s_active, 0);

	atomic_set(&sd->s_event, 1);

	INIT_LIST_HEAD(&sd->s_children);

	INIT_LIST_HEAD(&sd->s_sibling);



	sd->s_name = name;

	sd->s_mode = mode;
@@ -273,7 +313,7 @@ void sysfs_attach_dirent(struct sysfs_dirent *sd, 


	if (parent_sd) {

		sd->s_parent = sysfs_get(parent_sd);

		list_add(&sd->s_sibling, &parent_sd->s_children);

		sysfs_link_sibling(sd);

	}

}
@@ -289,7 +329,7 @@ int sysfs_dirent_exist(struct sysfs_dirent *parent_sd, 
{

	struct sysfs_dirent * sd;



	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {

	for (sd = parent_sd->s_children; sd; sd = sd->s_sibling) {

		if (sd->s_type) {

			if (strcmp(sd->s_name, new))

				continue;
@@ -409,7 +449,7 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry, 
	struct inode *inode;

	int found = 0;



	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {

	for (sd = parent_sd->s_children; sd; sd = sd->s_sibling) {

		if ((sd->s_type & SYSFS_NOT_PINNED) &&

		    !strcmp(sd->s_name, dentry->d_name.name)) {

			found = 1;
@@ -458,7 +498,7 @@ static void remove_dir(struct dentry * d) 


	mutex_lock(&parent->d_inode->i_mutex);



 	list_del_init(&sd->s_sibling);

	sysfs_unlink_sibling(sd);



	pr_debug(" o %s removing done (%d)\n",d->d_name.name,

		 atomic_read(&d->d_count));
@@ -478,9 +518,9 @@ void sysfs_remove_subdir(struct dentry * d) 


static void __sysfs_remove_dir(struct dentry *dentry)

{

	LIST_HEAD(removed);

	struct sysfs_dirent *removed = NULL;

	struct sysfs_dirent *parent_sd;

	struct sysfs_dirent * sd, * tmp;

	struct sysfs_dirent **pos;



	if (!dentry)

		return;
@@ -488,15 +528,25 @@ static void __sysfs_remove_dir(struct dentry *dentry) 
	pr_debug("sysfs %s: removing dir\n",dentry->d_name.name);

	mutex_lock(&dentry->d_inode->i_mutex);

	parent_sd = dentry->d_fsdata;

	list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {

		if (!sd->s_type || !(sd->s_type & SYSFS_NOT_PINNED))

			continue;

		list_move(&sd->s_sibling, &removed);

	pos = &parent_sd->s_children;

	while (*pos) {

		struct sysfs_dirent *sd = *pos;



		if (sd->s_type && (sd->s_type & SYSFS_NOT_PINNED)) {

			*pos = sd->s_sibling;

			sd->s_sibling = removed;

			removed = sd;

		} else

			pos = &(*pos)->s_sibling;

	}

	mutex_unlock(&dentry->d_inode->i_mutex);



	list_for_each_entry_safe(sd, tmp, &removed, s_sibling) {

		list_del_init(&sd->s_sibling);

	while (removed) {

		struct sysfs_dirent *sd = removed;



		removed = sd->s_sibling;

		sd->s_sibling = NULL;



		sysfs_drop_dentry(sd);

		sysfs_deactivate(sd);

		sysfs_put(sd);
@@ -577,11 +627,11 @@ int sysfs_rename_dir(struct kobject * kobj, struct dentry *new_parent, 
	d_add(new_dentry, NULL);

	d_move(kobj->dentry, new_dentry);



	list_del_init(&sd->s_sibling);

	sysfs_unlink_sibling(sd);

	sysfs_get(parent_sd);

	sysfs_put(sd->s_parent);

	sd->s_parent = parent_sd;

	list_add(&sd->s_sibling, &parent_sd->s_children);

	sysfs_link_sibling(sd);



	error = 0;

	goto out_unlock;
@@ -633,11 +683,11 @@ again: 
	dput(new_dentry);



	/* Remove from old parent's list and insert into new parent's list. */

	list_del_init(&sd->s_sibling);

	sysfs_unlink_sibling(sd);

	sysfs_get(new_parent_sd);

	sysfs_put(sd->s_parent);

	sd->s_parent = new_parent_sd;

	list_add(&sd->s_sibling, &new_parent_sd->s_children);

	sysfs_link_sibling(sd);



out:

	mutex_unlock(&new_parent_dentry->d_inode->i_mutex);
@@ -668,7 +718,7 @@ static int sysfs_dir_close(struct inode *inode, struct file *file) 
	struct sysfs_dirent * cursor = file->private_data;



	mutex_lock(&dentry->d_inode->i_mutex);

	list_del_init(&cursor->s_sibling);

	sysfs_unlink_sibling(cursor);

	mutex_unlock(&dentry->d_inode->i_mutex);



	release_sysfs_dirent(cursor);
@@ -687,7 +737,7 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) 
	struct dentry *dentry = filp->f_path.dentry;

	struct sysfs_dirent * parent_sd = dentry->d_fsdata;

	struct sysfs_dirent *cursor = filp->private_data;

	struct list_head *p, *q = &cursor->s_sibling;

	struct sysfs_dirent **pos;

	ino_t ino;

	int i = filp->f_pos;
@@ -710,16 +760,21 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) 
			i++;

			/* fallthrough */

		default:

			pos = &parent_sd->s_children;

			while (*pos != cursor)

				pos = &(*pos)->s_sibling;



			/* unlink cursor */

			*pos = cursor->s_sibling;



			if (filp->f_pos == 2)

				list_move(q, &parent_sd->s_children);

				pos = &parent_sd->s_children;



			for (p=q->next; p!= &parent_sd->s_children; p=p->next) {

				struct sysfs_dirent *next;

			for ( ; *pos; pos = &(*pos)->s_sibling) {

				struct sysfs_dirent *next = *pos;

				const char * name;

				int len;



				next = list_entry(p, struct sysfs_dirent,

						   s_sibling);

				if (!next->s_type)

					continue;
@@ -729,12 +784,14 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) 


				if (filldir(dirent, name, len, filp->f_pos, ino,

						 dt_type(next)) < 0)

					return 0;

					break;



				list_move(q, p);

				p = q;

				filp->f_pos++;

			}



			/* put cursor back in */

			cursor->s_sibling = *pos;

			*pos = cursor;

	}

	return 0;

}
@@ -759,20 +816,21 @@ static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin) 
		if (file->f_pos >= 2) {

			struct sysfs_dirent *sd = dentry->d_fsdata;

			struct sysfs_dirent *cursor = file->private_data;

			struct list_head *p;

			struct sysfs_dirent **pos;

			loff_t n = file->f_pos - 2;



			list_del(&cursor->s_sibling);

			p = sd->s_children.next;

			while (n && p != &sd->s_children) {

				struct sysfs_dirent *next;

				next = list_entry(p, struct sysfs_dirent,

						   s_sibling);

			sysfs_unlink_sibling(cursor);



			pos = &sd->s_children;

			while (n && *pos) {

				struct sysfs_dirent *next = *pos;

				if (next->s_type)

					n--;

				p = p->next;

				pos = &(*pos)->s_sibling;

			}

			list_add_tail(&cursor->s_sibling, p);



			cursor->s_sibling = *pos;

			*pos = cursor;

		}

	}

	mutex_unlock(&dentry->d_inode->i_mutex);

fs/sysfs/inode.c

+7 −5
Original line number Diff line number Diff line
@@ -284,8 +284,8 @@ void sysfs_drop_dentry(struct sysfs_dirent *sd) 


int sysfs_hash_and_remove(struct dentry * dir, const char * name)

{

	struct sysfs_dirent * sd;

	struct sysfs_dirent * parent_sd;

	struct sysfs_dirent **pos, *sd;

	struct sysfs_dirent *parent_sd = dir->d_fsdata;

	int found = 0;



	if (!dir)
@@ -295,13 +295,15 @@ int sysfs_hash_and_remove(struct dentry * dir, const char * name) 
		/* no inode means this hasn't been made visible yet */

		return -ENOENT;



	parent_sd = dir->d_fsdata;

	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);

	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {

	for (pos = &parent_sd->s_children; *pos; pos = &(*pos)->s_sibling) {

		sd = *pos;



		if (!sd->s_type)

			continue;

		if (!strcmp(sd->s_name, name)) {

			list_del_init(&sd->s_sibling);

			*pos = sd->s_sibling;

			sd->s_sibling = NULL;

			found = 1;

			break;

		}

fs/sysfs/mount.c

+0 −3
Original line number Diff line number Diff line
@@ -26,11 +26,8 @@ static const struct super_operations sysfs_ops = { 


static struct sysfs_dirent sysfs_root = {

	.s_count	= ATOMIC_INIT(1),

	.s_sibling	= LIST_HEAD_INIT(sysfs_root.s_sibling),

	.s_children	= LIST_HEAD_INIT(sysfs_root.s_children),

	.s_type		= SYSFS_ROOT,

	.s_mode		= S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,

	.s_iattr	= NULL,

	.s_ino		= 1,

};

fs/sysfs/sysfs.h

+2 −2
Original line number Diff line number Diff line
@@ -23,8 +23,8 @@ struct sysfs_dirent { 
	atomic_t		s_count;

	atomic_t		s_active;

	struct sysfs_dirent	* s_parent;

	struct list_head	s_sibling;

	struct list_head	s_children;

	struct sysfs_dirent	* s_sibling;

	struct sysfs_dirent	* s_children;

	const char		* s_name;



	union {

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