ovl: store ovl_entry in inode->i_private for all inodes

Previously this was only done for directory inodes.  Doing so for all
inodes makes for a nice cleanup in ovl_permission at zero cost.

Inodes are not shared for hard links on the overlay, so this works fine.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/inode.c

@@ -109,31 +109,12 @@ static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
 
 int ovl_permission(struct inode *inode, int mask)
 {
-	struct ovl_entry *oe;
-	struct dentry *alias = NULL;
-	struct inode *realinode;
-	struct dentry *realdentry;
+	struct ovl_entry *oe = inode->i_private;
 	bool is_upper;
+	struct dentry *realdentry = ovl_entry_real(oe, &is_upper);
+	struct inode *realinode;
 	int err;
 
-	if (S_ISDIR(inode->i_mode)) {
-		oe = inode->i_private;
-	} else if (mask & MAY_NOT_BLOCK) {
-		return -ECHILD;
-	} else {
-		/*
-		 * For non-directories find an alias and get the info
-		 * from there.
-		 */
-		alias = d_find_any_alias(inode);
-		if (WARN_ON(!alias))
-			return -ENOENT;
-
-		oe = alias->d_fsdata;
-	}
-
-	realdentry = ovl_entry_real(oe, &is_upper);
-
 	if (ovl_is_default_permissions(inode)) {
 		struct kstat stat;
 		struct path realpath = { .dentry = realdentry };
@@ -145,26 +126,23 @@ int ovl_permission(struct inode *inode, int mask)
 
 		err = vfs_getattr(&realpath, &stat);
 		if (err)
-			goto out_dput;
+			return err;
 
-		err = -ESTALE;
 		if ((stat.mode ^ inode->i_mode) & S_IFMT)
-			goto out_dput;
+			return -ESTALE;
 
 		inode->i_mode = stat.mode;
 		inode->i_uid = stat.uid;
 		inode->i_gid = stat.gid;
 
-		err = generic_permission(inode, mask);
-		goto out_dput;
+		return generic_permission(inode, mask);
 	}
 
 	/* Careful in RCU walk mode */
-	realinode = ACCESS_ONCE(realdentry->d_inode);
+	realinode = d_inode_rcu(realdentry);
 	if (!realinode) {
 		WARN_ON(!(mask & MAY_NOT_BLOCK));
-		err = -ENOENT;
-		goto out_dput;
+		return -ENOENT;
 	}
 
 	if (mask & MAY_WRITE) {
@@ -183,16 +161,12 @@ int ovl_permission(struct inode *inode, int mask)
 		 * constructed return EROFS to prevent modification of
 		 * upper layer.
 		 */
-		err = -EROFS;
 		if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
 		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
-			goto out_dput;
+			return -EROFS;
 	}
 
-	err = __inode_permission(realinode, mask);
-out_dput:
-	dput(alias);
-	return err;
+	return __inode_permission(realinode, mask);
 }
 
 static const char *ovl_get_link(struct dentry *dentry,
@@ -405,11 +379,11 @@ struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
 	inode->i_ino = get_next_ino();
 	inode->i_mode = mode;
 	inode->i_flags |= S_NOATIME | S_NOCMTIME;
+	inode->i_private = oe;
 
 	mode &= S_IFMT;
 	switch (mode) {
 	case S_IFDIR:
-		inode->i_private = oe;
 		inode->i_op = &ovl_dir_inode_operations;
 		inode->i_fop = &ovl_dir_operations;
 		break;