linux-kernel - Re: [PATCH v3] NFSv4.0: nfs4_do_fsinfo() should not do implicit lease renewals

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Date:   Mon, 30 Dec 2019 10:36:32 -0500
From:   Chuck Lever <chuck.lever@...cle.com>
To:     Robert Milkowski <rmilkowski@...il.com>
Cc:     Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] NFSv4.0: nfs4_do_fsinfo() should not do implicit lease
 renewals



> On Dec 30, 2019, at 10:20 AM, Robert Milkowski <rmilkowski@...il.com> wrote:
> 
> From: Robert Milkowski <rmilkowski@...il.com>
> 
> Currently, each time nfs4_do_fsinfo() is called it will do an implicit
> NFS4 lease renewal, which is not compliant with the NFS4 specification.
> This can result in a lease being expired by an NFS server.
> 
> Commit 83ca7f5ab31f ("NFS: Avoid PUTROOTFH when managing leases")
> introduced implicit client lease renewal in nfs4_do_fsinfo(),
> which can result in the NFSv4.0 lease to expire on a server side,
> and servers returning NFS4ERR_EXPIRED or NFS4ERR_STALE_CLIENTID.
> 
> This can easily be reproduced by frequently unmounting a sub-mount,
> then stat'ing it to get it mounted again, which will delay or even
> completely prevent client from sending RENEW operations if no other
> NFS operations are issued. Eventually nfs server will expire client's
> lease and return an error on file access or next RENEW.
> 
> This can also happen when a sub-mount is automatically unmounted
> due to inactivity (after nfs_mountpoint_expiry_timeout), then it is
> mounted again via stat(). This can result in a short window during
> which client's lease will expire on a server but not on a client.
> This specific case was observed on production systems.
> 
> This patch makes an explicit lease renewal instead of an implicit one,
> by adding RENEW to a compound operation issued by nfs4_do_fsinfo(),
> similarly to NFSv4.1 which adds SEQUENCE operation.
> 
> Fixes: 83ca7f5ab31f ("NFS: Avoid PUTROOTFH when managing leases")
> Signed-off-by: Robert Milkowski <rmilkowski@...il.com>

Reviewed-by: Chuck Lever <chuck.lever@...cle.com>


> ---
> fs/nfs/nfs4proc.c       |  4 ++++
> fs/nfs/nfs4xdr.c        | 13 +++++++++++--
> include/linux/nfs_xdr.h |  3 +++
> 3 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 76d3716..6d075f0 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -4998,12 +4998,16 @@ static int nfs4_proc_statfs(struct nfs_server *server, struct nfs_fh *fhandle, s
> static int _nfs4_do_fsinfo(struct nfs_server *server, struct nfs_fh *fhandle,
> 		struct nfs_fsinfo *fsinfo)
> {
> +	struct nfs_client *clp = server->nfs_client;
> 	struct nfs4_fsinfo_arg args = {
> 		.fh = fhandle,
> 		.bitmask = server->attr_bitmask,
> +		.clientid = clp->cl_clientid,
> +		.renew = nfs4_has_session(clp) ? 0 : 1,		/* append RENEW */
> 	};
> 	struct nfs4_fsinfo_res res = {
> 		.fsinfo = fsinfo,
> +		.renew = nfs4_has_session(clp) ? 0 : 1,
> 	};
> 	struct rpc_message msg = {
> 		.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_FSINFO],
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index 936c577..0ce9a10 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -555,11 +555,13 @@ static int decode_layoutget(struct xdr_stream *xdr, struct rpc_rqst *req,
> #define NFS4_enc_fsinfo_sz	(compound_encode_hdr_maxsz + \
> 				encode_sequence_maxsz + \
> 				encode_putfh_maxsz + \
> -				encode_fsinfo_maxsz)
> +				encode_fsinfo_maxsz + \
> +				encode_renew_maxsz)
> #define NFS4_dec_fsinfo_sz	(compound_decode_hdr_maxsz + \
> 				decode_sequence_maxsz + \
> 				decode_putfh_maxsz + \
> -				decode_fsinfo_maxsz)
> +				decode_fsinfo_maxsz + \
> +				decode_renew_maxsz)
> #define NFS4_enc_renew_sz	(compound_encode_hdr_maxsz + \
> 				encode_renew_maxsz)
> #define NFS4_dec_renew_sz	(compound_decode_hdr_maxsz + \
> @@ -2646,6 +2648,8 @@ static void nfs4_xdr_enc_fsinfo(struct rpc_rqst *req, struct xdr_stream *xdr,
> 	encode_sequence(xdr, &args->seq_args, &hdr);
> 	encode_putfh(xdr, args->fh, &hdr);
> 	encode_fsinfo(xdr, args->bitmask, &hdr);
> +	if (args->renew)
> +		encode_renew(xdr, args->clientid, &hdr);
> 	encode_nops(&hdr);
> }
> 
> @@ -6778,6 +6782,11 @@ static int nfs4_xdr_dec_fsinfo(struct rpc_rqst *req, struct xdr_stream *xdr,
> 		status = decode_putfh(xdr);
> 	if (!status)
> 		status = decode_fsinfo(xdr, res->fsinfo);
> +	if (status)
> +		goto out;
> +	if (res->renew)
> +		status = decode_renew(xdr);
> +out:
> 	return status;
> }
> 
> diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
> index 72d5695..49bd673 100644
> --- a/include/linux/nfs_xdr.h
> +++ b/include/linux/nfs_xdr.h
> @@ -1025,11 +1025,14 @@ struct nfs4_fsinfo_arg {
> 	struct nfs4_sequence_args	seq_args;
> 	const struct nfs_fh *		fh;
> 	const u32 *			bitmask;
> +	clientid4			clientid;
> +	unsigned char			renew:1;
> };
> 
> struct nfs4_fsinfo_res {
> 	struct nfs4_sequence_res	seq_res;
> 	struct nfs_fsinfo	       *fsinfo;
> +	unsigned char			renew:1;
> };
> 
> struct nfs4_getattr_arg {
> -- 
> 1.8.3.1
> 
> 

--
Chuck Lever