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Date: Tue, 15 Sep 2026 08:39:22 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, cem@kernel.org, stable@vger.kernel.org,
	linux-xfs@vger.kernel.org
Subject: Re: [PATCH 6/6] xfs: check di_forkoff correctly in scrub
Message-ID: <20260915063922.GB13345@lst.de>
References: <178910161988.174887.8958318922224347752.stgit@frogsfrogsfrogs> <178910162147.174887.15828411239184280666.stgit@frogsfrogsfrogs> <20260911150745.GA26822@lst.de> <20260911155919.GG6265@frogsfrogsfrogs>
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On Fri, Sep 11, 2026 at 08:59:19AM -0700, Darrick J. Wong wrote:
> On Fri, Sep 11, 2026 at 05:07:45PM +0200, Christoph Hellwig wrote:
> > On Thu, Sep 10, 2026 at 10:54:58PM -0700, Darrick J. Wong wrote:
> > > The di_forkoff check in xchk_dinode is incorrect, according to LOLLM.
> > > XFS_DFORK_BOFF returns a byte count relative to the start of the literal
> > > area, not the start of the inode.  Therefore, this check won't flag
> > > di_forkoff values that are larger than the literal area but not the
> > > inode size itself.  Fix this check; sadly the old APTR code was correct.
> > 
> > The fi looks good, but I really which we could encapsulate this
> > magic >> 3 a bit better (here and elsewhere).
> 
> I /did/ think about adding a cleanup to do:
> 
> #define XFS_B_TO_FORKOFF(b)	((b) >> 3)
> #define XFS_FORKOFF_TO_B(f)	((f) << 3)
> 
> and then code like this:

That would be nice.  Especially with a comment explaining the odd
encoding a bit more.