Re: [RFC PATCH] fs: introduce check for drop/inc_nlink

[cheng.lin130]

> On Fri, Oct 13, 2023 at 03:27:30PM +0800, cheng.lin130@xxxxxxxxxx wrote:
> > From: Cheng Lin <cheng.lin130@xxxxxxxxxx>
> >
> > Avoid inode nlink overflow or underflow.
> >
> > Signed-off-by: Cheng Lin <cheng.lin130@xxxxxxxxxx>
> > ---
> I'm very confused. There's no explanation why that's needed. As it
> stands it's not possible to provide a useful review.
> I'm not saying it's wrong. I just don't understand why and even if this
> should please show up in the commit message.
In an xfs issue, there was an nlink underflow of a directory inode. There
is a key information in the kernel messages, that is the WARN_ON from
drop_nlink(). However, VFS did not prevent the underflow. I'm not sure
if this behavior is inadvertent or specifically designed. As an abnormal
situation, perhaps prohibiting nlink overflow or underflow is a better way
to handle it.
Request for your comment.