get rid of kern_path_parent()

all callers want the same thing, actually - a kinda-sorta analog of
kern_path_create().  I.e. they want parent vfsmount/dentry (with
->i_mutex held, to make sure the child dentry is still their child)
+ the child dentry.

Signed-off-by Al Viro <viro@zeniv.linux.org.uk>

Change-Id: I58cc7b0a087646516db9af69962447d27fb3ee8b

drivers/base/devtmpfs.c

@@ -227,33 +227,24 @@ static int handle_create(const char *nodename, umode_t mode, struct device *dev)
 
 static int dev_rmdir(const char *name)
 {
-	struct nameidata nd;
+	struct path parent;
 	struct dentry *dentry;
 	int err;
 
-	err = kern_path_parent(name, &nd);
+	dentry = kern_path_locked(name, &parent);
-	if (err)
+	if (IS_ERR(dentry))
-		return err;
+		return PTR_ERR(dentry);
-
+	if (dentry->d_inode) {
-	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+		if (dentry->d_inode->i_private == &thread)
-	dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
+			err = vfs_rmdir(parent.dentry->d_inode, dentry);
-	if (!IS_ERR(dentry)) {
+		else
-		if (dentry->d_inode) {
+			err = -EPERM;
-			if (dentry->d_inode->i_private == &thread)
-				err = vfs_rmdir(nd.path.dentry->d_inode,
-						dentry);
-			else
-				err = -EPERM;
-		} else {
-			err = -ENOENT;
-		}
-		dput(dentry);
 	} else {
-		err = PTR_ERR(dentry);
+		err = -ENOENT;
 	}
-
+	dput(dentry);
-	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+	mutex_unlock(&parent.dentry->d_inode->i_mutex);
-	path_put(&nd.path);
+	path_put(&parent);
 	return err;
 }
 
@@ -305,50 +296,43 @@ static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *sta
 
 static int handle_remove(const char *nodename, struct device *dev)
 {
-	struct nameidata nd;
+	struct path parent;
 	struct dentry *dentry;
-	struct kstat stat;
 	int deleted = 1;
 	int err;
 
-	err = kern_path_parent(nodename, &nd);
+	dentry = kern_path_locked(nodename, &parent);
-	if (err)
+	if (IS_ERR(dentry))
-		return err;
+		return PTR_ERR(dentry);
 
-	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+	if (dentry->d_inode) {
-	dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
+		struct kstat stat;
-	if (!IS_ERR(dentry)) {
+		err = vfs_getattr(parent.mnt, dentry, &stat);
-		if (dentry->d_inode) {
+		if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
-			err = vfs_getattr(nd.path.mnt, dentry, &stat);
+			struct iattr newattrs;
-			if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
+			/*
-				struct iattr newattrs;
+			 * before unlinking this node, reset permissions
-				/*
+			 * of possible references like hardlinks
-				 * before unlinking this node, reset permissions
+			 */
-				 * of possible references like hardlinks
+			newattrs.ia_uid = 0;
-				 */
+			newattrs.ia_gid = 0;
-				newattrs.ia_uid = 0;
+			newattrs.ia_mode = stat.mode & ~0777;
-				newattrs.ia_gid = 0;
+			newattrs.ia_valid =
-				newattrs.ia_mode = stat.mode & ~0777;
+				ATTR_UID|ATTR_GID|ATTR_MODE;
-				newattrs.ia_valid =
+			mutex_lock(&dentry->d_inode->i_mutex);
-					ATTR_UID|ATTR_GID|ATTR_MODE;
+			notify_change(dentry, &newattrs);
-				mutex_lock(&dentry->d_inode->i_mutex);
+			mutex_unlock(&dentry->d_inode->i_mutex);
-				notify_change(dentry, &newattrs);
+			err = vfs_unlink(parent.dentry->d_inode, dentry);
-				mutex_unlock(&dentry->d_inode->i_mutex);
+			if (!err || err == -ENOENT)
-				err = vfs_unlink(nd.path.dentry->d_inode,
+				deleted = 1;
-						 dentry);
-				if (!err || err == -ENOENT)
-					deleted = 1;
-			}
-		} else {
-			err = -ENOENT;
 		}
-		dput(dentry);
 	} else {
-		err = PTR_ERR(dentry);
+		err = -ENOENT;
 	}
-	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+	dput(dentry);
+	mutex_unlock(&parent.dentry->d_inode->i_mutex);
 
-	path_put(&nd.path);
+	path_put(&parent);
 	if (deleted && strchr(nodename, '/'))
 		delete_path(nodename);
 	return err;

fs/namei.c

@@ -1808,9 +1808,27 @@ static int do_path_lookup(int dfd, const char *name,
 	return retval;
 }
 
-int kern_path_parent(const char *name, struct nameidata *nd)
+/* does lookup, returns the object with parent locked */
+struct dentry *kern_path_locked(const char *name, struct path *path)
 {
-	return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
+	struct nameidata nd;
+	struct dentry *d;
+	int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd);
+	if (err)
+		return ERR_PTR(err);
+	if (nd.last_type != LAST_NORM) {
+		path_put(&nd.path);
+		return ERR_PTR(-EINVAL);
+	}
+	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+	d = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
+	if (IS_ERR(d)) {
+		mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+		path_put(&nd.path);
+		return d;
+	}
+	*path = nd.path;
+	return d;
 }
 
 int kern_path(const char *name, unsigned int flags, struct path *path)

include/linux/namei.h

@@ -78,7 +78,7 @@ extern int kern_path(const char *, unsigned, struct path *);
 
 extern struct dentry *kern_path_create(int, const char *, struct path *, int);
 extern struct dentry *user_path_create(int, const char __user *, struct path *, int);
-extern int kern_path_parent(const char *, struct nameidata *);
+extern struct dentry *kern_path_locked(const char *, struct path *);
 extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
 			   const char *, unsigned int, struct path *);
 

kernel/audit_watch.c

@@ -355,34 +355,15 @@ static void audit_remove_parent_watches(struct audit_parent *parent)
 /* Get path information necessary for adding watches. */
 static int audit_get_nd(struct audit_watch *watch, struct path *parent)
 {
-	struct nameidata nd;
+	struct dentry *d = kern_path_locked(watch->path, parent);
-	struct dentry *d;
+	if (IS_ERR(d))
-	int err;
-
-	err = kern_path_parent(watch->path, &nd);
-	if (err)
-		return err;
-
-	if (nd.last_type != LAST_NORM) {
-		path_put(&nd.path);
-		return -EINVAL;
-	}
-
-	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
-	d = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
-	if (IS_ERR(d)) {
-		mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
-		path_put(&nd.path);
 		return PTR_ERR(d);
-	}
+	mutex_unlock(&parent->dentry->d_inode->i_mutex);
 	if (d->d_inode) {
 		/* update watch filter fields */
 		watch->dev = d->d_inode->i_sb->s_dev;
 		watch->ino = d->d_inode->i_ino;
 	}
-	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
-
-	*parent = nd.path;
 	dput(d);
 	return 0;
 }