linux-kernel - Re: [PATCH] nfsd: delete unreachable confusing code in nfs4_open

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Message-ID: <419d4afc0fecb5cc87d1d0265642e6c99236e85e.camel@kernel.org>
Date: Mon, 29 Sep 2025 14:18:04 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Matvey Kovalev <matvey.kovalev@...ras.ru>, Chuck Lever
	 <chuck.lever@...cle.com>
Cc: 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,
 lvc-project@...uxtesting.org
Subject: Re: [PATCH] nfsd: delete unreachable confusing code in
 nfs4_open_delegation()

On Mon, 2025-09-29 at 20:35 +0300, Matvey Kovalev wrote:
> op_delegate_type is assigned OPEN_DELEGATE_NONE just before the if-block
> where condition specifies it not be equal to OPEN_DELEGATE_NONE. Compiler
> treats the block as unreachable and optimizes it out from the resulting
> executable.
> 
> In that aspect commit d08d32e6e5c0 ("nfsd4: return delegation immediately
> if lease fails") notably makes no difference.
> 
> Seems it's better to just drop this code instead of fiddling with memory
> barriers or atomics.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Matvey Kovalev <matvey.kovalev@...ras.ru>
> ---
>  fs/nfsd/nfs4state.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 88c347957da5b..debc6c8fef956 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -6284,11 +6284,6 @@ nfs4_open_delegation(struct svc_rqst *rqstp, struct nfsd4_open *open,
>  	return;
>  out_no_deleg:
>  	open->op_delegate_type = OPEN_DELEGATE_NONE;
> -	if (open->op_claim_type == NFS4_OPEN_CLAIM_PREVIOUS &&
> -	    open->op_delegate_type != OPEN_DELEGATE_NONE) {
> -		dprintk("NFSD: WARNING: refusing delegation reclaim\n");
> -		open->op_recall = true;
> -	}
>  
>  	/* 4.1 client asking for a delegation? */
>  	if (open->op_deleg_want)

Well spotted!

Reviewed-by: Jeff Layton <jlayton@...nel.org>