ovl: treat special files like a regular fs

No sense in opening special files on the underlying layers, they work just
as well if opened on the overlay.

Side effect is that it's no longer possible to connect one side of a pipe
opened on overlayfs with the other side opened on the underlying layer.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/dir.c

@@ -537,7 +537,7 @@ static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 		goto out;
 
 	err = -ENOMEM;
-	inode = ovl_new_inode(dentry->d_sb, mode);
+	inode = ovl_new_inode(dentry->d_sb, mode, rdev);
 	if (!inode)
 		goto out_drop_write;
 

fs/overlayfs/inode.c

@@ -333,7 +333,7 @@ static const struct inode_operations ovl_symlink_inode_operations = {
 	.update_time	= ovl_update_time,
 };
 
-static void ovl_fill_inode(struct inode *inode, umode_t mode)
+static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
 {
 	inode->i_ino = get_next_ino();
 	inode->i_mode = mode;
@@ -342,8 +342,11 @@ static void ovl_fill_inode(struct inode *inode, umode_t mode)
 	inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
 #endif
 
-	mode &= S_IFMT;
-	switch (mode) {
+	switch (mode & S_IFMT) {
+	case S_IFREG:
+		inode->i_op = &ovl_file_inode_operations;
+		break;
+
 	case S_IFDIR:
 		inode->i_op = &ovl_dir_inode_operations;
 		inode->i_fop = &ovl_dir_operations;
@@ -354,26 +357,19 @@ static void ovl_fill_inode(struct inode *inode, umode_t mode)
 		break;
 
 	default:
-		WARN(1, "illegal file type: %i\n", mode);
-		/* Fall through */
-
-	case S_IFREG:
-	case S_IFSOCK:
-	case S_IFBLK:
-	case S_IFCHR:
-	case S_IFIFO:
 		inode->i_op = &ovl_file_inode_operations;
+		init_special_inode(inode, mode, rdev);
 		break;
 	}
 }
 
-struct inode *ovl_new_inode(struct super_block *sb, umode_t mode)
+struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
 {
 	struct inode *inode;
 
 	inode = new_inode(sb);
 	if (inode)
-		ovl_fill_inode(inode, mode);
+		ovl_fill_inode(inode, mode, rdev);
 
 	return inode;
 }
@@ -397,7 +393,7 @@ struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)
 	inode = iget5_locked(sb, (unsigned long) realinode,
 			     ovl_inode_test, ovl_inode_set, realinode);
 	if (inode && inode->i_state & I_NEW) {
-		ovl_fill_inode(inode, realinode->i_mode);
+		ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
 		set_nlink(inode, realinode->i_nlink);
 		unlock_new_inode(inode);
 	}

fs/overlayfs/overlayfs.h

@@ -195,7 +195,7 @@ int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags);
 int ovl_update_time(struct inode *inode, struct timespec *ts, int flags);
 bool ovl_is_private_xattr(const char *name);
 
-struct inode *ovl_new_inode(struct super_block *sb, umode_t mode);
+struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev);
 struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode);
 static inline void ovl_copyattr(struct inode *from, struct inode *to)
 {

fs/overlayfs/super.c

@@ -304,7 +304,7 @@ static struct dentry *ovl_d_real(struct dentry *dentry,
 {
 	struct dentry *real;
 
-	if (d_is_dir(dentry)) {
+	if (!d_is_reg(dentry)) {
 		if (!inode || inode == d_inode(dentry))
 			return dentry;
 		goto bug;
@@ -575,7 +575,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		if (upperdentry && !d_is_dir(upperdentry)) {
 			inode = ovl_get_inode(dentry->d_sb, realinode);
 		} else {
-			inode = ovl_new_inode(dentry->d_sb, realinode->i_mode);
+			inode = ovl_new_inode(dentry->d_sb, realinode->i_mode,
+					      realinode->i_rdev);
 			if (inode)
 				ovl_inode_init(inode, realinode, !!upperdentry);
 		}
@@ -1324,7 +1325,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_fs_info = ufs;
 	sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK;
 
-	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR));
+	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
 	if (!root_dentry)
 		goto out_free_oe;