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Date: Mon, 5 Oct 2026 15:13:46 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Carlos Maiolino <cem@kernel.org>,
	Jens Axboe <axboe@kernel.dk>,
	Christian Brauner <brauner@kernel.org>, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 17/21] xfs: verify data checksums during media
 verification
Message-ID: <20261005131346.GE26805@lst.de>
References: <20260924100032.2733101-1-hch@lst.de> <20260924100032.2733101-18-hch@lst.de> <20260929011936.GY2705364@frogsfrogsfrogs>
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On Mon, Sep 28, 2026 at 06:19:36PM -0700, Darrick J. Wong wrote:
> > +xfs_submit_verify_bio_csum(
> 
> What's the return value convention here?  1 for media error, 0 for
> success, or negative errno if we failed to issue the read?

Yeah:

/* returns 0 for success, 1 for media error, or -errno for other errors */


> > +	bno = xfs_daddr_to_rtb(mp, *daddr);
> > +	end = xfs_daddr_to_rtb(mp, *daddr + *bbcount);
> 
> It occurs to me that xfs_daddr_to_rtb rounds its argument down.  So if
> you pass in daddr==0 and bbcount==2, you'll get bno==end==0 and do no
> verification.  I would hope that callers won't pass in parameters like
> that, but who knows?
> 
> So I think this should be:
> 
> 	end = xfs_daddr_to_rtb(mp,
> 			*daddr + *bbcount + XFS_FSB_TO_BB(mp, 1) - 1);
> 
> Which I admit is a bit gross.

Not too horrible.  We should also check for a 0 len after rounding in
case nothing is left.