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Commit ea015218 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

kernfs: Add support for always empty directories. 



Add a new function kernfs_create_empty_dir that can be used to create
directory that can not be modified.

Update the code to use make_empty_dir_inode when reporting a
permanently empty directory to the vfs.

Update the code to not allow adding to permanently empty directories.

Cc: stable@vger.kernel.org
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent eb6d38d5

fs/kernfs/dir.c

+37 −1
Original line number Diff line number Diff line
@@ -585,6 +585,9 @@ int kernfs_add_one(struct kernfs_node *kn) 
		goto out_unlock;



	ret = -ENOENT;

	if (parent->flags & KERNFS_EMPTY_DIR)

		goto out_unlock;



	if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))

		goto out_unlock;
@@ -776,6 +779,38 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent, 
	return ERR_PTR(rc);

}



/**

 * kernfs_create_empty_dir - create an always empty directory

 * @parent: parent in which to create a new directory

 * @name: name of the new directory

 *

 * Returns the created node on success, ERR_PTR() value on failure.

 */

struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,

					    const char *name)

{

	struct kernfs_node *kn;

	int rc;



	/* allocate */

	kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR, KERNFS_DIR);

	if (!kn)

		return ERR_PTR(-ENOMEM);



	kn->flags |= KERNFS_EMPTY_DIR;

	kn->dir.root = parent->dir.root;

	kn->ns = NULL;

	kn->priv = NULL;



	/* link in */

	rc = kernfs_add_one(kn);

	if (!rc)

		return kn;



	kernfs_put(kn);

	return ERR_PTR(rc);

}



static struct dentry *kernfs_iop_lookup(struct inode *dir,

					struct dentry *dentry,

					unsigned int flags)
@@ -1247,7 +1282,8 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent, 
	mutex_lock(&kernfs_mutex);



	error = -ENOENT;

	if (!kernfs_active(kn) || !kernfs_active(new_parent))

	if (!kernfs_active(kn) || !kernfs_active(new_parent) ||

	    (new_parent->flags & KERNFS_EMPTY_DIR))

		goto out;



	error = 0;

fs/kernfs/inode.c

+2 −0
Original line number Diff line number Diff line
@@ -296,6 +296,8 @@ static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) 
	case KERNFS_DIR:

		inode->i_op = &kernfs_dir_iops;

		inode->i_fop = &kernfs_dir_fops;

		if (kn->flags & KERNFS_EMPTY_DIR)

			make_empty_dir_inode(inode);

		break;

	case KERNFS_FILE:

		inode->i_size = kn->attr.size;

include/linux/kernfs.h

+3 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ enum kernfs_node_flag { 
	KERNFS_LOCKDEP		= 0x0100,

	KERNFS_SUICIDAL		= 0x0400,

	KERNFS_SUICIDED		= 0x0800,

	KERNFS_EMPTY_DIR	= 0x1000,

};



/* @flags for kernfs_create_root() */
@@ -285,6 +286,8 @@ void kernfs_destroy_root(struct kernfs_root *root); 
struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,

					 const char *name, umode_t mode,

					 void *priv, const void *ns);

struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,

					    const char *name);

struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,

					 const char *name,

					 umode_t mode, loff_t size,