Commit 13b3086d authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
Browse files

sysfs: add sysfs_dirent->s_parent 



Add sysfs_dirent->s_parent.  With this patch, each sd points to and
holds a reference to its parent.  This allows walking sysfs tree
without referencing sd->s_dentry which can go away anytime if the user
doesn't control when it's deleted.

sd->s_parent is initialized and parent is referenced in
sysfs_attach_dirent().  Reference to parent is released when the sd is
released, so as long as reference to a sd is held, s_parent can be
followed.

dentry walk in sysfs_readdir() is convereted to s_parent walk.

This will be used to reimplement symlink such that it uses only
sysfs_dirent tree.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent a26cd722

fs/sysfs/dir.c

+23 −7
Original line number Diff line number Diff line
@@ -47,6 +47,11 @@ static void sysfs_free_ino(ino_t ino) 


void release_sysfs_dirent(struct sysfs_dirent * sd)

{

	struct sysfs_dirent *parent_sd;



 repeat:

	parent_sd = sd->s_parent;



	if (sd->s_type & SYSFS_KOBJ_LINK) {

		struct sysfs_symlink * sl = sd->s_element;

		kfree(sl->link_name);
@@ -56,6 +61,10 @@ void release_sysfs_dirent(struct sysfs_dirent * sd) 
	kfree(sd->s_iattr);

	sysfs_free_ino(sd->s_ino);

	kmem_cache_free(sysfs_dir_cachep, sd);



	sd = parent_sd;

	if (sd && atomic_dec_and_test(&sd->s_count))

		goto repeat;

}



static void sysfs_d_iput(struct dentry * dentry, struct inode * inode)
@@ -119,9 +128,11 @@ void sysfs_attach_dirent(struct sysfs_dirent *sd, 
		dentry->d_op = &sysfs_dentry_ops;

	}



	if (parent_sd)

	if (parent_sd) {

		sd->s_parent = sysfs_get(parent_sd);

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

	}

}



/*

 *
@@ -571,7 +582,10 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) 
			i++;

			/* fallthrough */

		case 1:

			ino = parent_ino(dentry);

			if (parent_sd->s_parent)

				ino = parent_sd->s_parent->s_ino;

			else

				ino = parent_sd->s_ino;

			if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)

				break;

			filp->f_pos++;
@@ -688,13 +702,13 @@ int sysfs_make_shadowed_dir(struct kobject *kobj, 


struct dentry *sysfs_create_shadow_dir(struct kobject *kobj)

{

	struct dentry *dir = kobj->dentry;

	struct inode *inode = dir->d_inode;

	struct dentry *parent = dir->d_parent;

	struct sysfs_dirent *parent_sd = parent->d_fsdata;

	struct dentry *shadow;

	struct sysfs_dirent *sd;

	struct dentry *parent, *dir, *shadow;

	struct inode *inode;



	dir = kobj->dentry;

	inode = dir->d_inode;

	parent = dir->d_parent;

	shadow = ERR_PTR(-EINVAL);

	if (!sysfs_is_shadowed_inode(inode))

		goto out;
@@ -706,6 +720,8 @@ struct dentry *sysfs_create_shadow_dir(struct kobject *kobj) 
	sd = sysfs_new_dirent(kobj, inode->i_mode, SYSFS_DIR);

	if (!sd)

		goto nomem;

	/* point to parent_sd but don't attach to it */

	sd->s_parent = sysfs_get(parent_sd);

	sysfs_attach_dirent(sd, NULL, shadow);



	d_instantiate(shadow, igrab(inode));

fs/sysfs/mount.c

+1 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 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_element	= NULL,

fs/sysfs/sysfs.h

+1 −0
Original line number Diff line number Diff line 
struct sysfs_dirent {

	atomic_t		s_count;

	struct sysfs_dirent	* s_parent;

	struct list_head	s_sibling;

	struct list_head	s_children;

	void 			* s_element;

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