[patch 03/29] knfsd: add userspace controls for stats tables

[Greg Banks <gnb@sgi.com>]

Add two control files to /proc/fs/nfsd:

* "stats_enabled" can be used to disable or enable the gathering
   of per-client and per-export statistics in the server.

* "stats_prune_period" can be used to set the period at
   which the pruning timer runs, in seconds.  Unused stats
   entries will survive at most twice that time.

Signed-off-by: Greg Banks <gnb@sgi.com>
---

 fs/nfsd/nfsctl.c |   99 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)

Index: bfields/fs/nfsd/nfsctl.c
===================================================================
--- bfields.orig/fs/nfsd/nfsctl.c
+++ bfields/fs/nfsd/nfsctl.c
@@ -64,6 +64,8 @@ enum {
 	NFSD_Versions,
 	NFSD_Ports,
 	NFSD_MaxBlkSize,
+	NFSD_Stats_Enabled,
+	NFSD_Stats_Prune_Period,
 	/*
 	 * The below MUST come last.  Otherwise we leave a hole in nfsd_files[]
 	 * with !CONFIG_NFSD_V4 and simple_fill_super() goes oops
@@ -92,6 +94,8 @@ static ssize_t write_pool_threads(struct
 static ssize_t write_versions(struct file *file, char *buf, size_t size);
 static ssize_t write_ports(struct file *file, char *buf, size_t size);
 static ssize_t write_maxblksize(struct file *file, char *buf, size_t size);
+static ssize_t write_stats_enabled(struct file *file, char *buf, size_t size);
+static ssize_t write_stats_prune_period(struct file *file, char *buf, size_t size);
 #ifdef CONFIG_NFSD_V4
 static ssize_t write_leasetime(struct file *file, char *buf, size_t size);
 static ssize_t write_recoverydir(struct file *file, char *buf, size_t size);
@@ -113,6 +117,8 @@ static ssize_t (*write_op[])(struct file
 	[NFSD_Versions] = write_versions,
 	[NFSD_Ports] = write_ports,
 	[NFSD_MaxBlkSize] = write_maxblksize,
+	[NFSD_Stats_Enabled] = write_stats_enabled,
+	[NFSD_Stats_Prune_Period] = write_stats_prune_period,
 #ifdef CONFIG_NFSD_V4
 	[NFSD_Leasetime] = write_leasetime,
 	[NFSD_RecoveryDir] = write_recoverydir,
@@ -1121,6 +1127,97 @@ static ssize_t write_maxblksize(struct f
 	return sprintf(buf, "%d\n", nfsd_max_blksize);
 }
 
+extern int nfsd_stats_enabled;
+
+/**
+ * write_stats_enabled - Set or report whether per-client/
+ *			 per-export stats are enabled.
+ *
+ * Input:
+ *			buf:		ignored
+ *			size:		zero
+ *
+ * OR
+ *
+ * Input:
+ * 			buf:		C string containing an unsigned
+ * 					integer value representing the new value
+ *			size:		non-zero length of C string in @buf
+ * Output:
+ *	On success:	passed-in buffer filled with '\n'-terminated C string
+ *			containing numeric value of the current setting
+ *			return code is the size in bytes of the string
+ *	On error:	return code is zero or a negative errno value
+ */
+static ssize_t write_stats_enabled(struct file *file, char *buf, size_t size)
+{
+	char *mesg = buf;
+	if (size > 0) {
+		int enabled;
+		int rv = get_int(&mesg, &enabled);
+		if (rv)
+			return rv;
+		/* check `enabled' against allowed range */
+		if (enabled < 0 || enabled > 1)
+			return -EINVAL;
+		/*
+		 * We can change the enabled flag at any time without
+		 * locking.  All it controls is whether stats are
+		 * gathered for new incoming NFS calls.  Old gathered
+		 * stats still sit around in the hash tables until
+		 * naturally pruned.
+		 */
+		nfsd_stats_enabled = enabled;
+	}
+	return sprintf(buf, "%d\n", nfsd_stats_enabled);
+}
+
+extern int nfsd_stats_prune_period;
+
+/**
+ * write_stats_prune_period - Set or report the period for pruning
+ *			      old per-client/per-export stats entries,
+ *			      in seconds.
+ *
+ * Input:
+ *			buf:		ignored
+ *			size:		zero
+ *
+ * OR
+ *
+ * Input:
+ * 			buf:		C string containing an unsigned
+ * 					integer value representing the new value
+ *			size:		non-zero length of C string in @buf
+ * Output:
+ *	On success:	passed-in buffer filled with '\n'-terminated C string
+ *			containing numeric value of the current setting
+ *			return code is the size in bytes of the string
+ *	On error:	return code is zero or a negative errno value
+ */
+static ssize_t write_stats_prune_period(struct file *file, char *buf, size_t size)
+{
+	char *mesg = buf;
+	if (size > 0) {
+		int period;
+		int rv = get_int(&mesg, &period);
+		if (rv)
+			return rv;
+		/* check `period' against allowed range */
+		if (period < 10 || period > 14*86400)
+			return -EINVAL;
+		/*
+		 * We can change the period at any time without
+		 * locking.  All it controls is the timeout on the
+		 * next run of the prune timer.  This might cause
+		 * some unexpected behaviour if the period is
+		 * changed from really high to really low.
+		 */
+		nfsd_stats_prune_period = period;
+	}
+	return sprintf(buf, "%d\n", nfsd_stats_prune_period);
+}
+
 #ifdef CONFIG_NFSD_V4
 extern time_t nfs4_leasetime(void);
 
@@ -1263,6 +1360,8 @@ static int nfsd_fill_super(struct super_
 		[NFSD_Versions] = {"versions", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Ports] = {"portlist", &transaction_ops, S_IWUSR|S_IRUGO},
 		[NFSD_MaxBlkSize] = {"max_block_size", &transaction_ops, S_IWUSR|S_IRUGO},
+		[NFSD_Stats_Enabled] = {"stats_enabled", &transaction_ops, S_IWUSR|S_IRUGO},
+		[NFSD_Stats_Prune_Period] = {"stats_prune_period", &transaction_ops, S_IWUSR|S_IRUGO},
 #ifdef CONFIG_NFSD_V4
 		[NFSD_Leasetime] = {"nfsv4leasetime", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_RecoveryDir] = {"nfsv4recoverydir", &transaction_ops, S_IWUSR|S_IRUSR},

--
Greg