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Message-ID: <5d9bbb599569ce29f16e4e0eef6b291eda0f375b.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: Tue, 12 Dec 2023 07:07:37 -0500
In-Reply-To: <a30b00df8b40ca94d0ff243c0305f36c7cbafc43.camel@kernel.org>
References: <cover.1694436263.git.lorenzo@kernel.org>
	 <ac18892ea3f718c63f0a12e39aeaac812c081515.1694436263.git.lorenzo@kernel.org>
	 <a30b00df8b40ca94d0ff243c0305f36c7cbafc43.camel@kernel.org>
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On Mon, 2023-12-11 at 13:56 -0500, Jeff Layton wrote:
> 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_i=
d);
> > +	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;
> >  }
>=20
> 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.
>=20
> Is it possible to stash a pointer to the serv while we hold the
> reference?
>=20

Actually, it looks like Neil may have already fixed this in the series
he sent on Oct 29th. See:

    [PATCH 3/5] nfsd: hold nfsd_mutex across entire netlink operation

Another reason to go ahead and get that series in...

> > =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_s=
eq,
> > +			  &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
>=20
> I think there is a potential race above. Once you've=20
>=20
>=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_ver=
sion4;
> > 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 rp=
c
> > +	 * 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(=
struct nfs4_stid *s)
> > =20
> >  /* Maximum number of slots per session. 160 is useful for long haul TC=
P */
> >  #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

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