Re: [PATCH] xfs: introduce protection for drop nlink

[<cheng.lin130@zte.com.cn>]

> On Fri, Aug 25, 2023 at 10:56:27AM -0700, Darrick J. Wong wrote:
> > On Fri, Aug 25, 2023 at 05:09:20PM +0800, cheng.lin130@zte.com.cn wrote:
> > > > On Thu, Aug 24, 2023 at 03:43:52PM +0800, cheng.lin130@zte.com.cn wrote:
> > > >> From: Cheng Lin <cheng.lin130@zte.com.cn>
> > > >> An dir nlinks overflow which down form 0 to 0xffffffff, cause the
> > > >> directory to become unusable until the next xfs_repair run.
> > > > Hmmm.  How does this ever happen?
> > > > IMO, if it does happen, we need to fix whatever bug that causes it
> > > > to happen, not issue a warning and do nothing about the fact we
> > > > just hit a corrupt inode state...
> > > Yes, I'm very agree with your opinion. But I don't know how it happened,
> > > and how to reproduce it.
> >
> > Wait, is this the result of a customer problem?  Or static analysis?
It's a customer problem.

> >
> > > >> Introduce protection for drop nlink to reduce the impact of this.
> > > >> And produce a warning for directory nlink error during remove.
> > > >>
> > > >> Signed-off-by: Cheng Lin <cheng.lin130@zte.com.cn>
> > > >> ---
> > > >>  fs/xfs/xfs_inode.c | 16 +++++++++++++++-
> > > >>  1 file changed, 15 insertions(+), 1 deletion(-)
> > > >>
> > > >> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> > > >> index 9e62cc5..536dbe4 100644
> > > >> --- a/fs/xfs/xfs_inode.c
> > > >> +++ b/fs/xfs/xfs_inode.c
> > > >> @@ -919,6 +919,15 @@ STATIC int xfs_iunlink_remove(struct xfs_trans *tp, struct xfs_perag *pag,
> >
> > I'm not sure why your diff program thinks this hunk is from
> > xfs_iunlink_remove, seeing as the line numbers of the chunk point to
> > xfs_droplink.  Maybe that's what's going on in this part of the thread?
> Yes.
> I don't expect patches to be mangled like this - I generally
> take the hunk prefix to indicate what code is being modified when
> reading patches, not expecting that the hunk is modifying code over
> a thousand lines prior to the function in the prefix...
> So, yeah, something went very wrong with the generation of this
> patch...
> -Dave.
It may be a problem with the git version. After using 2.18.1 instead of 1.8.3.1,
the patch looks normal.

> --
> Dave Chinner
> david@fromorbit.com

> > > Wait a second - this code doesn't match an upstream kernel. What
> > > kernel did you make this patch against?
> > It's kernel mainline linux-6.5-rc7

> ....and what did you use to generate the patch?  git diff?
>
> --D
It's  git format-patch 
git version 1.8.3.1