linux-kernel - Re: [PATCH v2] nfsd: Use correct error code when decoding extents

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Message-ID: <lqssee7hdp5bkty34idm6s6xz2hfxpbkthzgqgopc72vbyzrdx@egvanmm3llrg>
Date: Thu, 12 Jun 2025 18:57:18 +0300
From: Sergey Bashirov <sergeybashirov@...il.com>
To: Chuck Lever <chuck.lever@...cle.com>, 
	Christoph Hellwig <hch@...radead.org>
Cc: Jeff Layton <jlayton@...nel.org>, NeilBrown <neil@...wn.name>, 
	Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>, 
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Konstantin Evtushenko <koevtushenko@...dex.com>
Subject: Re: [PATCH v2] nfsd: Use correct error code when decoding extents

On Thu, Jun 12, 2025 at 09:10:11AM -0400, Chuck Lever wrote:
> On 6/12/25 3:00 AM, Christoph Hellwig wrote:
> > On Wed, Jun 11, 2025 at 11:55:02PM +0300, Sergey Bashirov wrote:
> >>  	if (nr_iomaps < 0)
> >> -		return nfserrno(nr_iomaps);
> >> +		return cpu_to_be32(-nr_iomaps);
> >
> > This still feels like an odd calling convention.  Maybe we should just
> > change the calling convention to return the __be32 encoded nfs errno
> > and have a separate output argument for the number of iomaps?
> >
> > Chuck, any preference?
> >
>
> I thought of using an output argument. This calling convention is not
> uncommon in NFS code, and I recall that Linus might prefer avoiding
> output arguments?
>
> If I were writing fresh code, I think I would use an output argument
> instead of folding results of two different types into a function's
> return value.

In general, I am ok with either of these two approaches. But I agree
with Christoph that the solution with a separate output argument seems
more natural to me. Should I submit the v3 patch with a separate output
argument?

--
Sergey Bashirov