Re: [PATCH] NFSD: add rpc_status entry in nfsd debug filesystem

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> On Mon, 2023-07-10 at 18:16 +0200, Lorenzo Bianconi wrote:
> > Introduce rpc_status entry in nfsd debug filesystem in order to dump
> > pending RPC requests debugging information.
> > 
> > Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=366
> > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > ---
> > Changes since RFCv1:
> > - riduce time holding nfsd_mutex bumping svc_serv refcoung in
> >   nfsd_rpc_status_open()
> > - dump rqstp->rq_stime
> > - add missing kdoc for nfsd_rpc_status_open()
> > ---
> >  fs/nfsd/nfs4proc.c |  4 +--
> >  fs/nfsd/nfsctl.c   | 10 ++++++
> >  fs/nfsd/nfsd.h     |  2 ++
> >  fs/nfsd/nfssvc.c   | 88 ++++++++++++++++++++++++++++++++++++++++++++++
> >  net/sunrpc/svc.c   |  2 +-
> >  5 files changed, 102 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > index 5ae670807449..a4dd1ef104c3 100644
> > --- a/fs/nfsd/nfs4proc.c
> > +++ b/fs/nfsd/nfs4proc.c
> > @@ -2452,8 +2452,6 @@ static inline void nfsd4_increment_op_stats(u32 opnum)
> >  
> >  static const struct nfsd4_operation nfsd4_ops[];
> >  
> > -static const char *nfsd4_op_name(unsigned opnum);
> > -
> >  /*
> >   * Enforce NFSv4.1 COMPOUND ordering rules:
> >   *
> > @@ -3583,7 +3581,7 @@ void warn_on_nonidempotent_op(struct nfsd4_op *op)
> >  	}
> >  }
> >  
> > -static const char *nfsd4_op_name(unsigned opnum)
> > +const char *nfsd4_op_name(unsigned 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 1b8b1aab9a15..629b4296e7c6 100644
> > --- a/fs/nfsd/nfsctl.c
> > +++ b/fs/nfsd/nfsctl.c
> > @@ -57,6 +57,8 @@ enum {
> >  	NFSD_RecoveryDir,
> >  	NFSD_V4EndGrace,
> >  #endif
> > +	NFSD_Rpc_Status,
> > +
> >  	NFSD_MaxReserved
> >  };
> >  
> > @@ -195,6 +197,13 @@ static inline struct net *netns(struct file *file)
> >  	return file_inode(file)->i_sb->s_fs_info;
> >  }
> >  
> > +static const struct file_operations nfsd_rpc_status_operations = {
> > +	.open		= nfsd_rpc_status_open,
> > +	.read		= seq_read,
> > +	.llseek		= seq_lseek,
> > +	.release	= nfsd_pool_stats_release,
> > +};
> > +
> >  /*
> >   * write_unlock_ip - Release all locks used by a client
> >   *
> > @@ -1400,6 +1409,7 @@ static int nfsd_fill_super(struct super_block *sb, struct fs_context *fc)
> >  		[NFSD_RecoveryDir] = {"nfsv4recoverydir", &transaction_ops, S_IWUSR|S_IRUSR},
> >  		[NFSD_V4EndGrace] = {"v4_end_grace", &transaction_ops, S_IWUSR|S_IRUGO},
> >  #endif
> > +		[NFSD_Rpc_Status] = {"rpc_status", &nfsd_rpc_status_operations, S_IRUGO},
> >  		/* last one */ {""}
> >  	};
> >  
> > diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> > index d88498f8b275..75a3e1d55bc8 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_pool_stats_release(struct inode *, struct file *);
> > +int		nfsd_rpc_status_open(struct inode *inode, struct file *file);
> >  void		nfsd_shutdown_threads(struct net *net);
> >  
> >  void		nfsd_put(struct net *net);
> > @@ -506,6 +507,7 @@ extern void nfsd4_ssc_init_umount_work(struct nfsd_net *nn);
> >  
> >  extern void nfsd4_init_leases_net(struct nfsd_net *nn);
> >  
> > +const char *nfsd4_op_name(unsigned opnum);
> >  #else /* CONFIG_NFSD_V4 */
> >  static inline int nfsd4_is_junction(struct dentry *dentry)
> >  {
> > diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> > index 2154fa63c5f2..ef1eb8b1c5bf 100644
> > --- a/fs/nfsd/nfssvc.c
> > +++ b/fs/nfsd/nfssvc.c
> > @@ -1147,3 +1147,91 @@ int nfsd_pool_stats_release(struct inode *inode, struct file *file)
> >  	mutex_unlock(&nfsd_mutex);
> >  	return ret;
> >  }
> > +
> > +static int nfsd_rpc_status_show(struct seq_file *m, void *v)
> > +{
> > +	struct inode *inode = file_inode(m->file);
> > +	struct nfsd_net *nn = net_generic(inode->i_sb->s_fs_info, nfsd_net_id);
> > +	int i;
> > +
> > +	rcu_read_lock();
> > +
> 
> Much nicer without all of the heavyweight locking, I think!
> 
> > +	for (i = 0; i < nn->nfsd_serv->sv_nrpools; i++) {
> > +		struct svc_rqst *rqstp;
> > +
> > +		seq_puts(m, "XID        | FLAGS      | PROG       |");
> > +		seq_puts(m, " VERS       | PROC\t| TS(us)\t   |");
> > +		seq_puts(m, " REMOTE - LOCAL IP ADDR");
> > +		seq_puts(m, "\t\t\t\t\t\t\t\t   | NFS4 COMPOUND OPS\n");
> 
> It may be best to just eliminate the header, or at the very least, only
> print it once by moving it outside of the for loop.

ack, right. I will just get rid of it.

> 
> > +		list_for_each_entry_rcu(rqstp,
> > +				&nn->nfsd_serv->sv_pools[i].sp_all_threads,
> > +				rq_all) {
> > +			if (!test_bit(RQ_BUSY, &rqstp->rq_flags))
> > +				continue;
> > +
> > +			seq_printf(m,
> > +				   "0x%08x | 0x%08lx | 0x%08x | NFSv%d      |"
> > +				   " %s\t| %016lld |",
> 
> I'd definitely get rid of the '|' delimiters. I think that it'd be best
> to just separate the fields by single spaces, as that will be simpler
> for scripts to parse. There are plenty of examples in the kernel that do
> that (/proc/locks, /proc/self/mountstats, etc.).

ack, I will fix it.

> 
> We can always write a simple shell or python script for nfs-utils that
> parses and pretty-prints the fields.

ack, I will do.

> 
> > +				   be32_to_cpu(rqstp->rq_xid), rqstp->rq_flags,
> > +				   rqstp->rq_prog, rqstp->rq_vers,
> > +				   svc_proc_name(rqstp),
> > +				   ktime_to_us(rqstp->rq_stime));
> > +
> > +			if (rqstp->rq_addr.ss_family == AF_INET) {
> > +				seq_printf(m, " %pI4 - %pI4\t\t\t\t\t\t\t   |",
> > +					   &((struct sockaddr_in *)&rqstp->rq_addr)->sin_addr,
> > +					   &((struct sockaddr_in *)&rqstp->rq_daddr)->sin_addr);
> > +			} else if (rqstp->rq_addr.ss_family == AF_INET6) {
> > +				seq_printf(m, " %pI6 - %pI6 |",
> > +					   &((struct sockaddr_in6 *)&rqstp->rq_addr)->sin6_addr,
> > +					   &((struct sockaddr_in6 *)&rqstp->rq_daddr)->sin6_addr);
> > +			} else {
> > +				seq_printf(m, " Unknown address family: %hu\n",
> 
> ...and if we're going to go for something machine-parseable, maybe just
> print this as "unknown:%hu". Also, I don't think you want the extra
> newline here.

ack, I will fix it.

Regards,
Lorenzo

> 
> > +					   rqstp->rq_addr.ss_family);
> > +				continue;
> > +			}
> > +#ifdef CONFIG_NFSD_V4
> > +			if (rqstp->rq_vers == NFS4_VERSION &&
> > +			    rqstp->rq_proc == NFSPROC4_COMPOUND) {
> > +				/* NFSv4 compund */
> > +				struct nfsd4_compoundargs *args = rqstp->rq_argp;
> > +				struct nfsd4_compoundres *resp = rqstp->rq_resp;
> > +
> > +				while (resp->opcnt < args->opcnt) {
> > +					struct nfsd4_op *op = &args->ops[resp->opcnt++];
> > +
> > +					seq_printf(m, " %s", nfsd4_op_name(op->opnum));
> > +				}
> > +			}
> > +#endif /* CONFIG_NFSD_V4 */
> > +			seq_puts(m, "\n");
> > +		}
> > +	}
> > +
> > +	rcu_read_unlock();
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * nfsd_rpc_status_open - Atomically copy a write verifier
> > + * @inode: entry inode pointer.
> > + * @file: entry file pointer.
> > + *
> > + * This routine dumps pending RPC requests info queued into nfs server.
> > + */
> > +int nfsd_rpc_status_open(struct inode *inode, struct file *file)
> > +{
> > +	struct nfsd_net *nn = net_generic(inode->i_sb->s_fs_info, nfsd_net_id);
> > +
> > +	mutex_lock(&nfsd_mutex);
> > +	if (!nn->nfsd_serv) {
> > +		mutex_unlock(&nfsd_mutex);
> > +		return -ENODEV;
> > +	}
> > +
> > +	svc_get(nn->nfsd_serv);
> > +	mutex_unlock(&nfsd_mutex);
> > +
> > +	return single_open(file, nfsd_rpc_status_show, inode->i_private);
> > +}
> > diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> > index 587811a002c9..44eac83b35a1 100644
> > --- a/net/sunrpc/svc.c
> > +++ b/net/sunrpc/svc.c
> > @@ -1629,7 +1629,7 @@ const char *svc_proc_name(const struct svc_rqst *rqstp)
> >  		return rqstp->rq_procinfo->pc_name;
> >  	return "unknown";
> >  }
> > -
> > +EXPORT_SYMBOL_GPL(svc_proc_name);
> >  
> >  /**
> >   * svc_encode_result_payload - mark a range of bytes as a result payload
> 
> -- 
> Jeff Layton <jlayton@kernel.org>

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