iget: introduce a function to register iget failure

Introduce a function to register failure in an inode construction path. This
includes marking the inode under construction as bad, unlocking it and
releasing it.

Signed-off-by: David Howells <[e-mail]>
Acked-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/filesystems/porting

···
 test and set for you.
 
 e.g.
-       inode = iget_locked(sb, ino);
-       if (inode->i_state & I_NEW) {
-               read_inode_from_disk(inode);
-               unlock_new_inode(inode);
-       }
+	inode = iget_locked(sb, ino);
+	if (inode->i_state & I_NEW) {
+		err = read_inode_from_disk(inode);
+		if (err < 0) {
+			iget_failed(inode);
+			return err;
+		}
+		unlock_new_inode(inode);
+	}
+
+Note that if the process of setting up a new inode fails, then iget_failed()
+should be called on the inode to render it dead, and an appropriate error
+should be passed back to the caller.
 
 ---
 [recommended]

fs/bad_inode.c

···
 }
 
 EXPORT_SYMBOL(is_bad_inode);
+
+/**
+ * iget_failed - Mark an under-construction inode as dead and release it
+ * @inode: The inode to discard
+ *
+ * Mark an under-construction inode as dead and release it.
+ */
+void iget_failed(struct inode *inode)
+{
+	make_bad_inode(inode);
+	unlock_new_inode(inode);
+	iput(inode);
+}
+EXPORT_SYMBOL(iget_failed);

include/linux/fs.h

···
 }
 
 extern void __iget(struct inode * inode);
+extern void iget_failed(struct inode *);
 extern void clear_inode(struct inode *);
 extern void destroy_inode(struct inode *);
 extern struct inode *new_inode(struct super_block *);