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Message-ID: <a30b00df8b40ca94d0ff243c0305f36c7cbafc43.camel@kernel.org>
Subject: Re: [PATCH v8 3/3] NFSD: add rpc_status netlink support
From: Jeff Layton <jlayton@kernel.org>
To: Lorenzo Bianconi <lorenzo@kernel.org>, linux-nfs@vger.kernel.org
Cc: lorenzo.bianconi@redhat.com, chuck.lever@oracle.com, neilb@suse.de, 
	netdev@vger.kernel.org
Date: Mon, 11 Dec 2023 13:56:08 -0500
In-Reply-To: <ac18892ea3f718c63f0a12e39aeaac812c081515.1694436263.git.lorenzo@kernel.org>
References: <cover.1694436263.git.lorenzo@kernel.org>
	 <ac18892ea3f718c63f0a12e39aeaac812c081515.1694436263.git.lorenzo@kernel.org>
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On Mon, 2023-09-11 at 14:49 +0200, Lorenzo Bianconi wrote:
> Introduce rpc_status netlink support for NFSD in order to dump pending
> RPC requests debugging information from userspace.
>=20
> Tested-by: Jeff Layton <jlayton@kernel.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  fs/nfsd/nfsctl.c           | 192 ++++++++++++++++++++++++++++++++++++-
>  fs/nfsd/nfsd.h             |  16 ++++
>  fs/nfsd/nfssvc.c           |  15 +++
>  fs/nfsd/state.h            |   2 -
>  include/linux/sunrpc/svc.h |   1 +
>  5 files changed, 222 insertions(+), 4 deletions(-)
>=20
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 1be66088849c..b862a759ea15 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -26,6 +26,7 @@
>  #include "pnfs.h"
>  #include "filecache.h"
>  #include "trace.h"
> +#include "nfs_netlink_gen.h"
> =20
>  /*
>   *	We have a single directory with several nodes in it.
> @@ -1497,17 +1498,199 @@ unsigned int nfsd_net_id;
> =20
>  int nfsd_server_nl_rpc_status_get_start(struct netlink_callback *cb)
>  {
> -	return 0;
> +	struct nfsd_net *nn =3D net_generic(sock_net(cb->skb->sk), nfsd_net_id)=
;
> +	int ret =3D -ENODEV;
> +
> +	mutex_lock(&nfsd_mutex);
> +	if (nn->nfsd_serv) {
> +		svc_get(nn->nfsd_serv);
> +		ret =3D 0;
> +	}
> +	mutex_unlock(&nfsd_mutex);
> +
> +	return ret;
>  }

I think there is a potential race above. Once you've dropped the
nfsd_mutex, there is no guarantee that the nn->nfsd_serv will still be
set when you come back to put the serv. That means that we could oops
when we hit the _done method below.

Is it possible to stash a pointer to the serv while we hold the
reference?

> =20
> -int nfsd_server_nl_rpc_status_get_done(struct netlink_callback *cb)
> +static int nfsd_genl_rpc_status_compose_msg(struct sk_buff *skb,
> +					    struct netlink_callback *cb,
> +					    struct nfsd_genl_rqstp *rqstp)
>  {
> +	void *hdr;
> +	int i;
> +
> +	hdr =3D genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq=
,
> +			  &nfsd_server_nl_family, NLM_F_MULTI,
> +			  NFSD_CMD_RPC_STATUS_GET);
> +	if (!hdr)
> +		return -ENOBUFS;
> +
> +	if (nla_put_be32(skb, NFSD_ATTR_RPC_STATUS_XID, rqstp->rq_xid) ||
> +	    nla_put_u32(skb, NFSD_ATTR_RPC_STATUS_FLAGS, rqstp->rq_flags) ||
> +	    nla_put_u32(skb, NFSD_ATTR_RPC_STATUS_PROG, rqstp->rq_prog) ||
> +	    nla_put_u32(skb, NFSD_ATTR_RPC_STATUS_PROC, rqstp->rq_proc) ||
> +	    nla_put_u8(skb, NFSD_ATTR_RPC_STATUS_VERSION, rqstp->rq_vers) ||
> +	    nla_put_s64(skb, NFSD_ATTR_RPC_STATUS_SERVICE_TIME,
> +			ktime_to_us(rqstp->rq_stime),
> +			NFSD_ATTR_RPC_STATUS_PAD))
> +		return -ENOBUFS;
> +
> +	switch (rqstp->saddr.sa_family) {
> +	case AF_INET: {
> +		const struct sockaddr_in *s_in, *d_in;
> +
> +		s_in =3D (const struct sockaddr_in *)&rqstp->saddr;
> +		d_in =3D (const struct sockaddr_in *)&rqstp->daddr;
> +		if (nla_put_in_addr(skb, NFSD_ATTR_RPC_STATUS_SADDR4,
> +				    s_in->sin_addr.s_addr) ||
> +		    nla_put_in_addr(skb, NFSD_ATTR_RPC_STATUS_DADDR4,
> +				    d_in->sin_addr.s_addr) ||
> +		    nla_put_be16(skb, NFSD_ATTR_RPC_STATUS_SPORT,
> +				 s_in->sin_port) ||
> +		    nla_put_be16(skb, NFSD_ATTR_RPC_STATUS_DPORT,
> +				 d_in->sin_port))
> +			return -ENOBUFS;
> +		break;
> +	}
> +	case AF_INET6: {
> +		const struct sockaddr_in6 *s_in, *d_in;
> +
> +		s_in =3D (const struct sockaddr_in6 *)&rqstp->saddr;
> +		d_in =3D (const struct sockaddr_in6 *)&rqstp->daddr;
> +		if (nla_put_in6_addr(skb, NFSD_ATTR_RPC_STATUS_SADDR6,
> +				     &s_in->sin6_addr) ||
> +		    nla_put_in6_addr(skb, NFSD_ATTR_RPC_STATUS_DADDR6,
> +				     &d_in->sin6_addr) ||
> +		    nla_put_be16(skb, NFSD_ATTR_RPC_STATUS_SPORT,
> +				 s_in->sin6_port) ||
> +		    nla_put_be16(skb, NFSD_ATTR_RPC_STATUS_DPORT,
> +				 d_in->sin6_port))
> +			return -ENOBUFS;
> +		break;
> +	}
> +	default:
> +		break;
> +	}
> +
> +	if (rqstp->opcnt) {
> +		struct nlattr *attr;
> +
> +		attr =3D nla_nest_start(skb, NFSD_ATTR_RPC_STATUS_COMPOND_OP);
> +		if (!attr)
> +			return -ENOBUFS;
> +
> +		for (i =3D 0; i < rqstp->opcnt; i++) {
> +			struct nlattr *op_attr;
> +
> +			op_attr =3D nla_nest_start(skb, i);
> +			if (!op_attr)
> +				return -ENOBUFS;
> +
> +			if (nla_put_u32(skb, NFSD_ATTR_RPC_STATUS_COMP_OP,
> +					rqstp->opnum[i]))
> +				return -ENOBUFS;
> +
> +			nla_nest_end(skb, op_attr);
> +		}
> +
> +		nla_nest_end(skb, attr);
> +	}
> +
> +	genlmsg_end(skb, hdr);
> +
>  	return 0;
>  }
> =20
>  int nfsd_server_nl_rpc_status_get_dumpit(struct sk_buff *skb,
>  					 struct netlink_callback *cb)
>  {
> +	struct nfsd_net *nn =3D net_generic(sock_net(skb->sk), nfsd_net_id);
> +	int i, ret, rqstp_index;
> +
> +	rcu_read_lock();
> +
> +	for (i =3D 0; i < nn->nfsd_serv->sv_nrpools; i++) {
> +		struct svc_rqst *rqstp;
> +
> +		if (i < cb->args[0]) /* already consumed */
> +			continue;
> +
> +		rqstp_index =3D 0;
> +		list_for_each_entry_rcu(rqstp,
> +				&nn->nfsd_serv->sv_pools[i].sp_all_threads,
> +				rq_all) {
> +			struct nfsd_genl_rqstp genl_rqstp;
> +			unsigned int status_counter;
> +
> +			if (rqstp_index++ < cb->args[1]) /* already consumed */
> +				continue;
> +			/*
> +			 * Acquire rq_status_counter before parsing the rqst
> +			 * fields. rq_status_counter is set to an odd value in
> +			 * order to notify the consumers the rqstp fields are
> +			 * meaningful.
> +			 */
> +			status_counter =3D
> +				smp_load_acquire(&rqstp->rq_status_counter);
> +			if (!(status_counter & 1))
> +				continue;
> +
> +			genl_rqstp.rq_xid =3D rqstp->rq_xid;
> +			genl_rqstp.rq_flags =3D rqstp->rq_flags;
> +			genl_rqstp.rq_vers =3D rqstp->rq_vers;
> +			genl_rqstp.rq_prog =3D rqstp->rq_prog;
> +			genl_rqstp.rq_proc =3D rqstp->rq_proc;
> +			genl_rqstp.rq_stime =3D rqstp->rq_stime;
> +			genl_rqstp.opcnt =3D 0;
> +			memcpy(&genl_rqstp.daddr, svc_daddr(rqstp),
> +			       sizeof(struct sockaddr));
> +			memcpy(&genl_rqstp.saddr, svc_addr(rqstp),
> +			       sizeof(struct sockaddr));
> +
> +#ifdef CONFIG_NFSD_V4
> +			if (rqstp->rq_vers =3D=3D NFS4_VERSION &&
> +			    rqstp->rq_proc =3D=3D NFSPROC4_COMPOUND) {
> +				/* NFSv4 compund */
> +				struct nfsd4_compoundargs *args;
> +				int j;
> +
> +				args =3D rqstp->rq_argp;
> +				genl_rqstp.opcnt =3D args->opcnt;
> +				for (j =3D 0; j < genl_rqstp.opcnt; j++)
> +					genl_rqstp.opnum[j] =3D
> +						args->ops[j].opnum;
> +			}
> +#endif /* CONFIG_NFSD_V4 */
> +
> +			/*
> +			 * Acquire rq_status_counter before reporting the rqst
> +			 * fields to the user.
> +			 */
> +			if (smp_load_acquire(&rqstp->rq_status_counter) !=3D
> +			    status_counter)
> +				continue;
> +
> +			ret =3D nfsd_genl_rpc_status_compose_msg(skb, cb,
> +							       &genl_rqstp);
> +			if (ret)
> +				goto out;
> +		}
> +	}
> +
> +	cb->args[0] =3D i;
> +	cb->args[1] =3D rqstp_index;
> +	ret =3D skb->len;
> +out:
> +	rcu_read_unlock();
> +
> +	return ret;
> +}
> +
> +int nfsd_server_nl_rpc_status_get_done(struct netlink_callback *cb)
> +{
> +	mutex_lock(&nfsd_mutex);
> +	nfsd_put(sock_net(cb->skb->sk));
> +	mutex_unlock(&nfsd_mutex);
> +
>  	return 0;
>  }
> =20

I think there is a potential race above. Once you've=20


> @@ -1605,6 +1788,10 @@ static int __init init_nfsd(void)
>  	retval =3D register_filesystem(&nfsd_fs_type);
>  	if (retval)
>  		goto out_free_all;
> +	retval =3D genl_register_family(&nfsd_server_nl_family);
> +	if (retval)
> +		goto out_free_all;
> +
>  	return 0;
>  out_free_all:
>  	nfsd4_destroy_laundry_wq();
> @@ -1629,6 +1816,7 @@ static int __init init_nfsd(void)
> =20
>  static void __exit exit_nfsd(void)
>  {
> +	genl_unregister_family(&nfsd_server_nl_family);
>  	unregister_filesystem(&nfsd_fs_type);
>  	nfsd4_destroy_laundry_wq();
>  	unregister_cld_notifier();
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 11c14faa6c67..d787bd38c053 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -62,6 +62,22 @@ struct readdir_cd {
>  	__be32			err;	/* 0, nfserr, or nfserr_eof */
>  };
> =20
> +/* Maximum number of operations per session compound */
> +#define NFSD_MAX_OPS_PER_COMPOUND	50
> +
> +struct nfsd_genl_rqstp {
> +	struct sockaddr daddr;
> +	struct sockaddr saddr;
> +	unsigned long rq_flags;
> +	ktime_t rq_stime;
> +	__be32 rq_xid;
> +	u32 rq_vers;
> +	u32 rq_prog;
> +	u32 rq_proc;
> +	/* NFSv4 compund */
> +	u32 opnum[NFSD_MAX_OPS_PER_COMPOUND];
> +	u16 opcnt;
> +};
> =20
>  extern struct svc_program	nfsd_program;
>  extern const struct svc_version	nfsd_version2, nfsd_version3, nfsd_versi=
on4;
> diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> index 1582af33e204..fad34a7325b3 100644
> --- a/fs/nfsd/nfssvc.c
> +++ b/fs/nfsd/nfssvc.c
> @@ -998,6 +998,15 @@ int nfsd_dispatch(struct svc_rqst *rqstp)
>  	if (!proc->pc_decode(rqstp, &rqstp->rq_arg_stream))
>  		goto out_decode_err;
> =20
> +	/*
> +	 * Release rq_status_counter setting it to an odd value after the rpc
> +	 * request has been properly parsed. rq_status_counter is used to
> +	 * notify the consumers if the rqstp fields are stable
> +	 * (rq_status_counter is odd) or not meaningful (rq_status_counter
> +	 * is even).
> +	 */
> +	smp_store_release(&rqstp->rq_status_counter, rqstp->rq_status_counter |=
 1);
> +
>  	rp =3D NULL;
>  	switch (nfsd_cache_lookup(rqstp, &rp)) {
>  	case RC_DOIT:
> @@ -1015,6 +1024,12 @@ int nfsd_dispatch(struct svc_rqst *rqstp)
>  	if (!proc->pc_encode(rqstp, &rqstp->rq_res_stream))
>  		goto out_encode_err;
> =20
> +	/*
> +	 * Release rq_status_counter setting it to an even value after the rpc
> +	 * request has been properly processed.
> +	 */
> +	smp_store_release(&rqstp->rq_status_counter, rqstp->rq_status_counter +=
 1);
> +
>  	nfsd_cache_update(rqstp, rp, rqstp->rq_cachetype, statp + 1);
>  out_cached_reply:
>  	return 1;
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index cbddcf484dba..41bdc913fa71 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -174,8 +174,6 @@ static inline struct nfs4_delegation *delegstateid(st=
ruct nfs4_stid *s)
> =20
>  /* Maximum number of slots per session. 160 is useful for long haul TCP =
*/
>  #define NFSD_MAX_SLOTS_PER_SESSION     160
> -/* Maximum number of operations per session compound */
> -#define NFSD_MAX_OPS_PER_COMPOUND	50
>  /* Maximum  session per slot cache size */
>  #define NFSD_SLOT_CACHE_SIZE		2048
>  /* Maximum number of NFSD_SLOT_CACHE_SIZE slots per session */
> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> index dbf5b21feafe..caa20defd255 100644
> --- a/include/linux/sunrpc/svc.h
> +++ b/include/linux/sunrpc/svc.h
> @@ -251,6 +251,7 @@ struct svc_rqst {
>  						 * net namespace
>  						 */
>  	void **			rq_lease_breaker; /* The v4 client breaking a lease */
> +	unsigned int		rq_status_counter; /* RPC processing counter */
>  };
> =20
>  /* bits for rq_flags */

--=20
Jeff Layton <jlayton@kernel.org>