linux-kernel - Re: [PATCH v5 01/10] nfsd: fix handling of delegated change attr in CB

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Message-ID: <83aad379-81fb-4e11-a462-e02fd536fda2@oracle.com>
Date: Sun, 19 Jan 2025 10:19:04 -0500
From: Chuck Lever <chuck.lever@...cle.com>
To: Jeff Layton <jlayton@...nel.org>
Cc: linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, Anna Schumaker <anna@...nel.org>,
        Trond Myklebust <trondmy@...nel.org>, Jonathan Corbet <corbet@....net>,
        Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
        Olga Kornievskaia <okorniev@...hat.com>, Neil Brown <neilb@...e.de>
Subject: Re: [PATCH v5 01/10] nfsd: fix handling of delegated change attr in
 CB_GETATTR

On 12/9/24 4:13 PM, Jeff Layton wrote:
> RFC8881, section 10.4.3 has some specific guidance as to how the
> delegated change attribute should be handled. We currently don't follow
> that guidance properly.
> 
> In particular, when the file is modified, the server always reports the
> initial change attribute + 1. Section 10.4.3 however indicates that it
> should be incremented on every GETATTR request from other clients.
> 
> Only request the change attribute until the file has been modified. If
> there is an outstanding delegation, then increment the cached change
> attribute on every GETATTR.
> 
> Signed-off-by: Jeff Layton <jlayton@...nel.org>

After review of LTS backport instructions in the candidate patches for
v6.14, this commit stuck out. Should it have a Fixes: or Cc: stable ?

How about

   Fixes: 6487a13b5c6b ("NFSD: add support for CB_GETATTR callback") ??


> ---
>   fs/nfsd/nfs4callback.c |  8 +++++---
>   fs/nfsd/nfs4xdr.c      | 15 +++++++++------
>   2 files changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> index 3877b53e429fd89899d7dc35086bee8bda6eed07..25acb8624b854f5d0d184efec660e1f72cad8885 100644
> --- a/fs/nfsd/nfs4callback.c
> +++ b/fs/nfsd/nfs4callback.c
> @@ -361,12 +361,14 @@ static void
>   encode_cb_getattr4args(struct xdr_stream *xdr, struct nfs4_cb_compound_hdr *hdr,
>   			struct nfs4_cb_fattr *fattr)
>   {
> -	struct nfs4_delegation *dp =
> -		container_of(fattr, struct nfs4_delegation, dl_cb_fattr);
> +	struct nfs4_delegation *dp = container_of(fattr, struct nfs4_delegation, dl_cb_fattr);
>   	struct knfsd_fh *fh = &dp->dl_stid.sc_file->fi_fhandle;
> +	struct nfs4_cb_fattr *ncf = &dp->dl_cb_fattr;
>   	u32 bmap[1];
>   
> -	bmap[0] = FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE;
> +	bmap[0] = FATTR4_WORD0_SIZE;
> +	if (!ncf->ncf_file_modified)
> +		bmap[0] |= FATTR4_WORD0_CHANGE;
>   
>   	encode_nfs_cb_opnum4(xdr, OP_CB_GETATTR);
>   	encode_nfs_fh4(xdr, fh);
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 53fac037611c05ff8ba2618f9e324a9cb54c3890..c8e8d3f0dff4bb5288186369aad821906e684db7 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2919,6 +2919,7 @@ struct nfsd4_fattr_args {
>   	struct kstat		stat;
>   	struct kstatfs		statfs;
>   	struct nfs4_acl		*acl;
> +	u64			change_attr;
>   #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
>   	void			*context;
>   	int			contextlen;
> @@ -3018,7 +3019,6 @@ static __be32 nfsd4_encode_fattr4_change(struct xdr_stream *xdr,
>   					 const struct nfsd4_fattr_args *args)
>   {
>   	const struct svc_export *exp = args->exp;
> -	u64 c;
>   
>   	if (unlikely(exp->ex_flags & NFSEXP_V4ROOT)) {
>   		u32 flush_time = convert_to_wallclock(exp->cd->flush_time);
> @@ -3029,9 +3029,7 @@ static __be32 nfsd4_encode_fattr4_change(struct xdr_stream *xdr,
>   			return nfserr_resource;
>   		return nfs_ok;
>   	}
> -
> -	c = nfsd4_change_attribute(&args->stat);
> -	return nfsd4_encode_changeid4(xdr, c);
> +	return nfsd4_encode_changeid4(xdr, args->change_attr);
>   }
>   
>   static __be32 nfsd4_encode_fattr4_size(struct xdr_stream *xdr,
> @@ -3556,11 +3554,16 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
>   	if (dp) {
>   		struct nfs4_cb_fattr *ncf = &dp->dl_cb_fattr;
>   
> -		if (ncf->ncf_file_modified)
> +		if (ncf->ncf_file_modified) {
> +			++ncf->ncf_initial_cinfo;
>   			args.stat.size = ncf->ncf_cur_fsize;
> -
> +		}
> +		args.change_attr = ncf->ncf_initial_cinfo;
>   		nfs4_put_stid(&dp->dl_stid);
> +	} else {
> +		args.change_attr = nfsd4_change_attribute(&args.stat);
>   	}
> +
>   	if (err)
>   		goto out_nfserr;
>   
> 


-- 
Chuck Lever