Re: [PATCH nfs-utils] nfsstat: display NFSv4 callback operation statistics

On 6/18/26 1:24 PM, Jeff Layton wrote:
> The kernel now maintains per-operation call counts for the NFSv4
> backchannel (callback) operations it sends to clients, and exports them
> through the server-stats netlink dump as a new proc4cb-ops nested
> attribute (one server-proc-entry per callback opcode, OP_CB_GETATTR
> through OP_CB_OFFLOAD).
> 
> Add a "Server nfs v4 callback operations" section to nfsstat that
> reports these counts. The data is only available over netlink -- the
> /proc interface exposes nothing equivalent (only the single
> wdeleg_getattr line, which corresponds to CB_GETATTR) -- so the section
> is displayed solely when the stats were fetched via netlink. This is
> detected by srvproc4cbinfo[0] being non-zero, which the netlink handler
> sets from the entry count and the /proc parsers never touch.
> 
> The counters are indexed directly by RFC 8881 callback opcode, so the
> name array carries placeholders for the unassigned opcodes 0-2 to keep
> the array index aligned with the opcode value, mirroring the kernel's
> cb_counter layout.
> 
> Signed-off-by: Jeff Layton <[email protected]>
> ---
> After the most recent review, we decided to add server side callback
> counts as a new feature for nfsstat. See the kernel patches here:
> 
> https://lore.kernel.org/linux-nfs/20260618-exportd-netlink-v5-0-e9aef947af3d-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org/
Committed... (tag: nfs-utils-2-9-2-rc5)

steved.> ---
>   support/include/nfsd_netlink.h |  1 +
>   utils/nfsstat/nfsstat.c        | 46 +++++++++++++++++++++++++++++++++++++++---
>   2 files changed, 44 insertions(+), 3 deletions(-)
> 
> diff --git a/support/include/nfsd_netlink.h b/support/include/nfsd_netlink.h
> index 3d076d173b1d..87da1d0bb21e 100644
> --- a/support/include/nfsd_netlink.h
> +++ b/support/include/nfsd_netlink.h
> @@ -254,6 +254,7 @@ enum {
>   	NFSD_A_SERVER_STATS_PROC3_OPS,
>   	NFSD_A_SERVER_STATS_PROC4_OPS,
>   	NFSD_A_SERVER_STATS_PROC4OPS_OPS,
> +	NFSD_A_SERVER_STATS_PROC4CB_OPS,
>   
>   	__NFSD_A_SERVER_STATS_MAX,
>   	NFSD_A_SERVER_STATS_MAX = (__NFSD_A_SERVER_STATS_MAX - 1)
> diff --git a/utils/nfsstat/nfsstat.c b/utils/nfsstat/nfsstat.c
> index f09e1d6a447f..6717be502a82 100644
> --- a/utils/nfsstat/nfsstat.c
> +++ b/utils/nfsstat/nfsstat.c
> @@ -44,6 +44,8 @@ enum {
>   	SRVPROC4_SZ = 2,
>   	CLTPROC4_SZ = 59,
>   	SRVPROC4OPS_SZ = 71,
> +	SRVPROC4CB_SZ = 16,	/* indexed by callback opcode; OP_CB_OFFLOAD == 15 */
> +	SRVPROC4CB_FIRST = 3,	/* first assigned callback opcode, OP_CB_GETATTR */
>   };
>   
>   static unsigned int	srvproc2info[SRVPROC2_SZ+2],
> @@ -60,6 +62,8 @@ static unsigned int	cltproc4info[CLTPROC4_SZ+2],
>   			cltproc4info_old[CLTPROC4_SZ+2];	/* NFSv4 call counts ([0] == 49) */
>   static unsigned int	srvproc4opsinfo[SRVPROC4OPS_SZ+2],
>   			srvproc4opsinfo_old[SRVPROC4OPS_SZ+2];	/* NFSv4 call counts ([0] == 59) */
> +static unsigned int	srvproc4cbinfo[SRVPROC4CB_SZ+2],
> +			srvproc4cbinfo_old[SRVPROC4CB_SZ+2];	/* NFSv4 callback op counts (netlink only, [0] == 16) */
>   static unsigned int	srvnetinfo[5], srvnetinfo_old[5];	/* 0  # of received packets
>   								 * 1  UDP packets
>   								 * 2  TCP packets
> @@ -207,6 +211,19 @@ static const char *     nfssrvproc4opname[SRVPROC4OPS_SZ] = {
>   	"write_same",
>   };
>   
> +/*
> + * NFSv4 callback (backchannel) operations, indexed directly by RFC 8881
> + * callback opcode.  Opcodes 0-2 are not assigned, so the first three slots
> + * are placeholders to keep the array index aligned with the opcode value;
> + * display starts at SRVPROC4CB_FIRST and never prints them.
> + */
> +static const char *	nfssrvproc4cbname[SRVPROC4CB_SZ] = {
> +	"op0-unused",	"op1-unused",	"op2-unused",	"cb_getattr",
> +	"cb_recall",	"cb_layoutrecall", "cb_notify",	"cb_push_deleg",
> +	"cb_recall_any","cb_recall_obj","cb_recall_slot", "cb_sequence",
> +	"cb_wants_cancel", "cb_notify_lock", "cb_notify_devid", "cb_offload",
> +};
> +
>   #define LABEL_srvnet		"Server packet stats:\n"
>   #define LABEL_srvrpc		"Server rpc stats:\n"
>   #define LABEL_srvrc		"Server reply cache:\n"
> @@ -217,6 +234,7 @@ static const char *     nfssrvproc4opname[SRVPROC4OPS_SZ] = {
>   #define LABEL_srvproc3		"Server nfs v3:\n"
>   #define LABEL_srvproc4		"Server nfs v4:\n"
>   #define LABEL_srvproc4ops	"Server nfs v4 operations:\n"
> +#define LABEL_srvproc4cb	"Server nfs v4 callback operations:\n"
>   #define LABEL_cltnet		"Client packet stats:\n"
>   #define LABEL_cltrpc		"Client rpc stats:\n"
>   #define LABEL_cltproc2		"Client nfs v2:\n"
> @@ -250,6 +268,7 @@ typedef struct statinfo {
>   					SRV(proc3,s),\
>   					SRV(proc4,s), \
>   					SRV(proc4ops,s),\
> +					SRV(proc4cb,s),\
>   					{ NULL, NULL, 0, NULL }\
>   				}
>   #define DECLARE_CLT(n, s...)  	static statinfo n##s[] = { \
> @@ -683,14 +702,24 @@ print_server_stats(int opt_prt)
>   					nfssrvproc4name, srvproc4info + 1,
>   					sizeof(nfssrvproc4name)/sizeof(char *));
>   				print_callstats(LABEL_srvproc4ops,
> -					nfssrvproc4opname, srvproc4opsinfo + 1,
> +					nfssrvproc4opname, srvproc4opsinfo + 1,
>   					sizeof(nfssrvproc4opname)/sizeof(char *));
> +				/*
> +				 * Callback op counts are only available via
> +				 * netlink; srvproc4cbinfo[0] is left zero when
> +				 * stats come from /proc.
> +				 */
> +				if (srvproc4cbinfo[0])
> +					print_callstats(LABEL_srvproc4cb,
> +						nfssrvproc4cbname + SRVPROC4CB_FIRST,
> +						srvproc4cbinfo + 1 + SRVPROC4CB_FIRST,
> +						SRVPROC4CB_SZ - SRVPROC4CB_FIRST);
>   			}
>   		}
>   	}
>   }
>   static void
> -print_client_stats(int opt_prt)
> +print_client_stats(int opt_prt)
>   {
>   	if (opt_prt & PRNT_NET) {
>   		if (opt_sleep && !has_rpcstats(cltnetinfo, 4)) {
> @@ -806,8 +835,13 @@ print_serv_list(int opt_prt)
>   					nfssrvproc4name, srvproc4info + 1,
>   					sizeof(nfssrvproc4name)/sizeof(char *));
>   				print_callstats_list("nfs v4 servop",
> -					nfssrvproc4opname, srvproc4opsinfo + 1,
> +					nfssrvproc4opname, srvproc4opsinfo + 1,
>   					sizeof(nfssrvproc4opname)/sizeof(char *));
> +				if (srvproc4cbinfo[0])
> +					print_callstats_list("nfs v4 cback",
> +						nfssrvproc4cbname + SRVPROC4CB_FIRST,
> +						srvproc4cbinfo + 1 + SRVPROC4CB_FIRST,
> +						SRVPROC4CB_SZ - SRVPROC4CB_FIRST);
>   			}
>   		}
>   	}
> @@ -1228,6 +1262,12 @@ static int stats_nl_handler(struct nl_msg *msg, void *arg)
>   				parse_one_proc_entry(attr, si->valptr,
>   						     SRVPROC4OPS_SZ);
>   			break;
> +		case NFSD_A_SERVER_STATS_PROC4CB_OPS:
> +			si = get_stat_info("proc4cb", info);
> +			if (si)
> +				parse_one_proc_entry(attr, si->valptr,
> +						     SRVPROC4CB_SZ);
> +			break;
>   		}
>   	}
>   
> 
> ---
> base-commit: e4342316f4c93e88cce1382560c36dafbf4df58e
> change-id: 20260618-nfsstat-nl-70d465ab493b
> 
> Best regards,