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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Neil Brown <neilb@suse.de>, Lorenzo Bianconi <lorenzo@kernel.org>
CC:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
        Jeff Layton <jlayton@kernel.org>
Subject: Re: [PATCH v6 3/3] NFSD: add rpc_status entry in nfsd debug
 filesystem
Thread-Topic: [PATCH v6 3/3] NFSD: add rpc_status entry in nfsd debug
 filesystem
Thread-Index: AQHZy2ZFk8tcJXUTiE2sgxvjOkAuPK/joD+AgABaVICAASjegA==
Date:   Fri, 11 Aug 2023 14:07:21 +0000
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References: <cover.1691656474.git.lorenzo@kernel.org>
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> On Aug 10, 2023, at 4:24 PM, NeilBrown <neilb@suse.de> wrote:
>=20
> On Fri, 11 Aug 2023, Chuck Lever wrote:
>> On Thu, Aug 10, 2023 at 10:39:21AM +0200, Lorenzo Bianconi wrote:
>>> Introduce rpc_status entry in nfsd debug filesystem in order to dump
>>> pending RPC requests debugging information.
>>>=20
>>> Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=3D366
>>> Reviewed-by: NeilBrown <neilb@suse.de>
>>> Reviewed-by: Jeff Layton <jlayton@kernel.org>
>>> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
>>> ---
>>> fs/nfsd/nfs4proc.c         |   4 +-
>>> fs/nfsd/nfsctl.c           |   9 +++
>>> fs/nfsd/nfsd.h             |   7 ++
>>> fs/nfsd/nfssvc.c           | 140 +++++++++++++++++++++++++++++++++++++
>>> include/linux/sunrpc/svc.h |   1 +
>>> net/sunrpc/svc.c           |   2 +-
>>> 6 files changed, 159 insertions(+), 4 deletions(-)
>>>=20
>>> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
>>> index aa4f21f92deb..ff5a1dddc0ed 100644
>>> --- a/fs/nfsd/nfs4proc.c
>>> +++ b/fs/nfsd/nfs4proc.c
>>> @@ -2496,8 +2496,6 @@ static inline void nfsd4_increment_op_stats(u32 o=
pnum)
>>>=20
>>> static const struct nfsd4_operation nfsd4_ops[];
>>>=20
>>> -static const char *nfsd4_op_name(unsigned opnum);
>>> -
>>> /*
>>>  * Enforce NFSv4.1 COMPOUND ordering rules:
>>>  *
>>> @@ -3627,7 +3625,7 @@ void warn_on_nonidempotent_op(struct nfsd4_op *op=
)
>>> }
>>> }
>>>=20
>>> -static const char *nfsd4_op_name(unsigned opnum)
>>> +const char *nfsd4_op_name(unsigned int opnum)
>>> {
>>> if (opnum < ARRAY_SIZE(nfsd4_ops))
>>> return nfsd4_ops[opnum].op_name;
>>> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
>>> index dad88bff3b9e..83eb5c6d894e 100644
>>> --- a/fs/nfsd/nfsctl.c
>>> +++ b/fs/nfsd/nfsctl.c
>>> @@ -47,6 +47,7 @@ enum {
>>> NFSD_MaxBlkSize,
>>> NFSD_MaxConnections,
>>> NFSD_Filecache,
>>> + NFSD_Rpc_Status,
>>> /*
>>> * The below MUST come last.  Otherwise we leave a hole in nfsd_files[]
>>> * with !CONFIG_NFSD_V4 and simple_fill_super() goes oops
>>> @@ -195,6 +196,13 @@ static inline struct net *netns(struct file *file)
>>> return file_inode(file)->i_sb->s_fs_info;
>>> }
>>>=20
>>> +static const struct file_operations nfsd_rpc_status_operations =3D {
>>> + .open =3D nfsd_rpc_status_open,
>>> + .read =3D seq_read,
>>> + .llseek =3D seq_lseek,
>>> + .release =3D nfsd_stats_release,
>>> +};
>>> +
>>> /*
>>>  * write_unlock_ip - Release all locks used by a client
>>>  *
>>> @@ -1394,6 +1402,7 @@ static int nfsd_fill_super(struct super_block *sb=
, struct fs_context *fc)
>>> [NFSD_MaxBlkSize] =3D {"max_block_size", &transaction_ops, S_IWUSR|S_IR=
UGO},
>>> [NFSD_MaxConnections] =3D {"max_connections", &transaction_ops, S_IWUSR=
|S_IRUGO},
>>> [NFSD_Filecache] =3D {"filecache", &nfsd_file_cache_stats_fops, S_IRUGO=
},
>>> + [NFSD_Rpc_Status] =3D {"rpc_status", &nfsd_rpc_status_operations, S_I=
RUGO},
>>> #ifdef CONFIG_NFSD_V4
>>> [NFSD_Leasetime] =3D {"nfsv4leasetime", &transaction_ops, S_IWUSR|S_IRU=
SR},
>>> [NFSD_Gracetime] =3D {"nfsv4gracetime", &transaction_ops, S_IWUSR|S_IRU=
SR},
>>> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
>>> index 55b9d85ed71b..3e8a47b93fd4 100644
>>> --- a/fs/nfsd/nfsd.h
>>> +++ b/fs/nfsd/nfsd.h
>>> @@ -94,6 +94,7 @@ int nfsd_get_nrthreads(int n, int *, struct net *);
>>> int nfsd_set_nrthreads(int n, int *, struct net *);
>>> int nfsd_pool_stats_open(struct inode *, struct file *);
>>> int nfsd_stats_release(struct inode *, struct file *);
>>> +int nfsd_rpc_status_open(struct inode *inode, struct file *file);
>>> void nfsd_shutdown_threads(struct net *net);
>>>=20
>>> static inline void nfsd_put(struct net *net)
>>> @@ -511,12 +512,18 @@ extern void nfsd4_ssc_init_umount_work(struct nfs=
d_net *nn);
>>>=20
>>> extern void nfsd4_init_leases_net(struct nfsd_net *nn);
>>>=20
>>> +const char *nfsd4_op_name(unsigned int opnum);
>>> #else /* CONFIG_NFSD_V4 */
>>> static inline int nfsd4_is_junction(struct dentry *dentry)
>>> {
>>> return 0;
>>> }
>>>=20
>>> +static inline const char *nfsd4_op_name(unsigned int opnum)
>>> +{
>>> + return "unknown_operation";
>>> +}
>>> +
>>> static inline void nfsd4_init_leases_net(struct nfsd_net *nn) { };
>>>=20
>>> #define register_cld_notifier() 0
>>> diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
>>> index 460219030ce1..237be14d3a11 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;
>>> @@ -1101,3 +1116,128 @@ int nfsd_stats_release(struct inode *inode, str=
uct file *file)
>>> mutex_unlock(&nfsd_mutex);
>>> return ret;
>>> }
>>> +
>>> +static int nfsd_rpc_status_show(struct seq_file *m, void *v)
>>> +{
>>> + struct inode *inode =3D file_inode(m->file);
>>> + struct nfsd_net *nn =3D net_generic(inode->i_sb->s_fs_info, nfsd_net_=
id);
>>> + int i;
>>> +
>>> + seq_puts(m, "# XID FLAGS VERS PROC TIMESTAMP SADDR SPORT DADDR DPORT =
COMPOUND_OPS\n");
>>> +
>>> + rcu_read_lock();
>>> +
>>> + for (i =3D 0; i < nn->nfsd_serv->sv_nrpools; i++) {
>>> + struct svc_rqst *rqstp;
>>> +
>>> + list_for_each_entry_rcu(rqstp,
>>> + &nn->nfsd_serv->sv_pools[i].sp_all_threads,
>>> + rq_all) {
>>> + struct {
>>> + struct sockaddr daddr;
>>> + struct sockaddr saddr;
>>> + unsigned long rq_flags;
>>> + const char *pc_name;
>>> + ktime_t rq_stime;
>>> + __be32 rq_xid;
>>> + u32 rq_vers;
>>> + /* NFSv4 compund */
>>> + u32 opnum[NFSD_MAX_OPS_PER_COMPOUND];
>>> + } rqstp_info;
>>> + unsigned int status_counter;
>>> + char buf[RPC_MAX_ADDRBUFLEN];
>>> + int opcnt =3D 0;
>>> +
>>> + /*
>>> + * 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;
>>> +
>>> + rqstp_info.rq_xid =3D rqstp->rq_xid;
>>> + rqstp_info.rq_flags =3D rqstp->rq_flags;
>>> + rqstp_info.rq_vers =3D rqstp->rq_vers;
>>> + rqstp_info.pc_name =3D svc_proc_name(rqstp);
>>> + rqstp_info.rq_stime =3D rqstp->rq_stime;
>>> + memcpy(&rqstp_info.daddr, svc_daddr(rqstp),
>>> +       sizeof(struct sockaddr));
>>> + memcpy(&rqstp_info.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 =3D rqstp->rq_argp;
>>> + int j;
>>> +
>>> + opcnt =3D args->opcnt;
>>> + for (j =3D 0; j < opcnt; j++) {
>>> + struct nfsd4_op *op =3D &args->ops[j];
>>> +
>>> + rqstp_info.opnum[j] =3D op->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;
>>> +
>>> + seq_printf(m,
>>> +   "%04u %04ld NFSv%d %s %016lld",
>>> +   be32_to_cpu(rqstp_info.rq_xid),
>>=20
>> It's proper to display XIDs as 8-hexit hexadecimal values, as you
>> did before. "0x%08x" is the correct format, as that matches the
>> XID display format used by Wireshark and our tracepoints.
>>=20
>>=20
>>> +   rqstp_info.rq_flags,
>>=20
>> I didn't mean for you to change the flags format to decimal. I was
>> trying to point out that the content of this field will need to be
>> displayed symbolically if we care about an easy user experience.
>>=20
>> Let's stick with hex here. A clever user can read the bits directly
>> from that. All others should have a tool that parses this field and
>> prints the list of bits in it symbolically.
>>=20
>>=20
>>> +   rqstp_info.rq_vers,
>>> +   rqstp_info.pc_name,
>>> +   ktime_to_us(rqstp_info.rq_stime));
>>> + seq_printf(m, " %s",
>>> +   __svc_print_addr(&rqstp_info.saddr, buf,
>>> +    sizeof(buf), false));
>>> + seq_printf(m, " %s",
>>> +   __svc_print_addr(&rqstp_info.daddr, buf,
>>> +    sizeof(buf), false));
>>> + if (opcnt) {
>>> + int j;
>>> +
>>> + seq_puts(m, " ");
>>> + for (j =3D 0; j < opcnt; j++)
>>> + seq_printf(m, "%s%s",
>>> +   nfsd4_op_name(rqstp_info.opnum[j]),
>>> +   j =3D=3D opcnt - 1 ? "" : ":");
>>> + } else {
>>> + seq_puts(m, " -");
>>> + }
>>=20
>> This looks correct to me.
>>=20
>> I'm leaning towards moving this to a netlink API that can be
>> extended over time to handle other stats and also act as an NFSD
>> control plane, similar to other network subsystems.
>>=20
>> Any comments, complaints or rotten fruit from anyone?
>=20
> I think netlink is the best way forward.  'cat' is nice, but not
> necessary.  We have an established path for distributing tools for
> working with nfsd so we get easily get a suitable tool into the hands of
> our users.
>=20
> The only fruit I have relates to the name "rpc_status", and it probably
> over-ripe rather than rotten :-)
> In the context of RPC, "status" means the success/failure result of a
> request.  That is not what this file provides.  It is a list of active
> requests.  So maybe "active_rpc".
> One advantage of netlink is that the API is based on numbers, not names!

There won't be a file name with netlink, so right, it won't be an
issue.

Lorenzo, can you proceed with netlink instead of /proc/fs/nfsd?=20
Maybe start with a yaml spec file?


> NeilBrown
>=20
>=20
>>=20
>>=20
>>> + seq_puts(m, "\n");
>>> + }
>>> + }
>>> +
>>> + rcu_read_unlock();
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +/**
>>> + * nfsd_rpc_status_open - open routine for nfsd_rpc_status handler
>>> + * @inode: entry inode pointer.
>>> + * @file: entry file pointer.
>>> + *
>>> + * nfsd_rpc_status_open is the open routine for nfsd_rpc_status procfs=
 handler.
>>> + * nfsd_rpc_status dumps pending RPC requests info queued into nfs ser=
ver.
>>> + */
>>> +int nfsd_rpc_status_open(struct inode *inode, struct file *file)
>>> +{
>>> + int ret =3D nfsd_stats_open(inode);
>>> +
>>> + if (ret)
>>> + return ret;
>>> +
>>> + return single_open(file, nfsd_rpc_status_show, inode->i_private);
>>> +}
>>> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
>>> index 7838b37bcfa8..b49c0470b4fe 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 */
>>> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
>>> index af692bff44ab..83bee19df104 100644
>>> --- a/net/sunrpc/svc.c
>>> +++ b/net/sunrpc/svc.c
>>> @@ -1656,7 +1656,7 @@ const char *svc_proc_name(const struct svc_rqst *=
rqstp)
>>> return rqstp->rq_procinfo->pc_name;
>>> return "unknown";
>>> }
>>> -
>>> +EXPORT_SYMBOL_GPL(svc_proc_name);
>>>=20
>>> /**
>>>  * svc_encode_result_payload - mark a range of bytes as a result payloa=
d
>>> --=20
>>> 2.41.0
>>>=20
>>=20
>> --=20
>> Chuck Lever
>>=20
>=20

--
Chuck Lever