[PATCH 07/11] staging: lustre: fold lprocfs_call_handler functionality into lnet_debugfs_*

[NeilBrown]

The calling convention for ->proc_handler is rather clumsy,
as a comment in fs/procfs/proc_sysctl.c confirms.
lustre has copied this convention to lnet_debugfs_{read,write},
and then provided a wrapper for handlers - lprocfs_call_handler -
to work around the clumsiness.

It is cleaner to just fold the functionality of lprocfs_call_handler()
into lnet_debugfs_* and let them call the final handler directly.

If these files were ever moved to /proc/sys (which seems unlikely) the
handling in fs/procfs/proc_sysctl.c would need to be fixed to, but
that would not be a bad thing.

So modify all the functions that did use the wrapper to not need it
now that a more sane calling convention is available.

Signed-off-by: NeilBrown <neilb@xxxxxxxx>
---
 .../staging/lustre/include/linux/libcfs/libcfs.h   |    4 -
 drivers/staging/lustre/lnet/libcfs/module.c        |   84 +++++++-------------
 drivers/staging/lustre/lnet/lnet/router_proc.c     |   41 +++-------
 3 files changed, 41 insertions(+), 88 deletions(-)

diff --git a/drivers/staging/lustre/include/linux/libcfs/libcfs.h b/drivers/staging/lustre/include/linux/libcfs/libcfs.h
index edc7ed0dcb94..7ac609328256 100644
--- a/drivers/staging/lustre/include/linux/libcfs/libcfs.h
+++ b/drivers/staging/lustre/include/linux/libcfs/libcfs.h
@@ -57,10 +57,6 @@ int libcfs_setup(void);
 extern struct workqueue_struct *cfs_rehash_wq;
 
 void lustre_insert_debugfs(struct ctl_table *table);
-int lprocfs_call_handler(void *data, int write, loff_t *ppos,
-			 void __user *buffer, size_t *lenp,
-			 int (*handler)(void *data, int write, loff_t pos,
-					void __user *buffer, int len));
 
 /*
  * Memory
diff --git a/drivers/staging/lustre/lnet/libcfs/module.c b/drivers/staging/lustre/lnet/libcfs/module.c
index 5dc7de9e6478..02c404c6738e 100644
--- a/drivers/staging/lustre/lnet/libcfs/module.c
+++ b/drivers/staging/lustre/lnet/libcfs/module.c
@@ -290,33 +290,15 @@ static struct miscdevice libcfs_dev = {
 
 static int libcfs_dev_registered;
 
-int lprocfs_call_handler(void *data, int write, loff_t *ppos,
-			 void __user *buffer, size_t *lenp,
-			 int (*handler)(void *data, int write, loff_t pos,
-					void __user *buffer, int len))
-{
-	int rc = handler(data, write, *ppos, buffer, *lenp);
-
-	if (rc < 0)
-		return rc;
-
-	if (write) {
-		*ppos += *lenp;
-	} else {
-		*lenp = rc;
-		*ppos += rc;
-	}
-	return 0;
-}
-EXPORT_SYMBOL(lprocfs_call_handler);
-
-static int __proc_dobitmasks(void *data, int write,
-			     loff_t pos, void __user *buffer, int nob)
+static int proc_dobitmasks(struct ctl_table *table, int write,
+			   void __user *buffer, size_t *lenp, loff_t *ppos)
 {
 	const int tmpstrlen = 512;
 	char *tmpstr;
 	int rc;
-	unsigned int *mask = data;
+	size_t nob = *lenp;
+	loff_t pos = *ppos;
+	unsigned int *mask = table->data;
 	int is_subsys = (mask == &libcfs_subsystem_debug) ? 1 : 0;
 	int is_printk = (mask == &libcfs_printk) ? 1 : 0;
 
@@ -351,32 +333,23 @@ static int __proc_dobitmasks(void *data, int write,
 	return rc;
 }
 
-static int proc_dobitmasks(struct ctl_table *table, int write,
-			   void __user *buffer, size_t *lenp, loff_t *ppos)
+static int proc_dump_kernel(struct ctl_table *table, int write,
+			    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-	return lprocfs_call_handler(table->data, write, ppos, buffer, lenp,
-				    __proc_dobitmasks);
-}
+	size_t nob = *lenp;
 
-static int __proc_dump_kernel(void *data, int write,
-			      loff_t pos, void __user *buffer, int nob)
-{
 	if (!write)
 		return 0;
 
 	return cfs_trace_dump_debug_buffer_usrstr(buffer, nob);
 }
 
-static int proc_dump_kernel(struct ctl_table *table, int write,
+static int proc_daemon_file(struct ctl_table *table, int write,
 			    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-	return lprocfs_call_handler(table->data, write, ppos, buffer, lenp,
-				    __proc_dump_kernel);
-}
+	size_t nob = *lenp;
+	loff_t pos = *ppos;
 
-static int __proc_daemon_file(void *data, int write,
-			      loff_t pos, void __user *buffer, int nob)
-{
 	if (!write) {
 		int len = strlen(cfs_tracefile);
 
@@ -390,13 +363,6 @@ static int __proc_daemon_file(void *data, int write,
 	return cfs_trace_daemon_command_usrstr(buffer, nob);
 }
 
-static int proc_daemon_file(struct ctl_table *table, int write,
-			    void __user *buffer, size_t *lenp, loff_t *ppos)
-{
-	return lprocfs_call_handler(table->data, write, ppos, buffer, lenp,
-				    __proc_daemon_file);
-}
-
 static int libcfs_force_lbug(struct ctl_table *table, int write,
 			     void __user *buffer,
 			     size_t *lenp, loff_t *ppos)
@@ -419,9 +385,11 @@ static int proc_fail_loc(struct ctl_table *table, int write,
 	return rc;
 }
 
-static int __proc_cpt_table(void *data, int write,
-			    loff_t pos, void __user *buffer, int nob)
+static int proc_cpt_table(struct ctl_table *table, int write,
+			  void __user *buffer, size_t *lenp, loff_t *ppos)
 {
+	size_t nob = *lenp;
+	loff_t pos = *ppos;
 	char *buf = NULL;
 	int len = 4096;
 	int rc  = 0;
@@ -457,13 +425,6 @@ static int __proc_cpt_table(void *data, int write,
 	return rc;
 }
 
-static int proc_cpt_table(struct ctl_table *table, int write,
-			  void __user *buffer, size_t *lenp, loff_t *ppos)
-{
-	return lprocfs_call_handler(table->data, write, ppos, buffer, lenp,
-				    __proc_cpt_table);
-}
-
 static struct ctl_table lnet_table[] = {
 	{
 		.procname = "debug",
@@ -573,10 +534,17 @@ static ssize_t lnet_debugfs_read(struct file *filp, char __user *buf,
 {
 	struct ctl_table *table = filp->private_data;
 	int error;
+	loff_t old_pos = *ppos;
 
 	error = table->proc_handler(table, 0, (void __user *)buf, &count, ppos);
-	if (!error)
+	/*
+	 * On success, the length read is either in error or in count.
+	 * If ppos changed, then use count, else use error
+	 */
+	if (!error && *ppos != old_pos)
 		error = count;
+	else if (error > 0)
+		*ppos += error;
 
 	return error;
 }
@@ -586,10 +554,14 @@ static ssize_t lnet_debugfs_write(struct file *filp, const char __user *buf,
 {
 	struct ctl_table *table = filp->private_data;
 	int error;
+	loff_t old_pos = *ppos;
 
 	error = table->proc_handler(table, 1, (void __user *)buf, &count, ppos);
-	if (!error)
+	if (!error) {
 		error = count;
+		if (*ppos == old_pos)
+			*ppos += count;
+	}
 
 	return error;
 }
diff --git a/drivers/staging/lustre/lnet/lnet/router_proc.c b/drivers/staging/lustre/lnet/lnet/router_proc.c
index ae4b7f5953a0..f135082fec5c 100644
--- a/drivers/staging/lustre/lnet/lnet/router_proc.c
+++ b/drivers/staging/lustre/lnet/lnet/router_proc.c
@@ -74,11 +74,13 @@
 
 #define LNET_PROC_VERSION(v)	((unsigned int)((v) & LNET_PROC_VER_MASK))
 
-static int __proc_lnet_stats(void *data, int write,
-			     loff_t pos, void __user *buffer, int nob)
+static int proc_lnet_stats(struct ctl_table *table, int write,
+			   void __user *buffer, size_t *lenp, loff_t *ppos)
 {
 	int rc;
 	struct lnet_counters *ctrs;
+	size_t nob = *lenp;
+	loff_t pos = *ppos;
 	int len;
 	char *tmpstr;
 	const int tmpsiz = 256; /* 7 %u and 4 %llu */
@@ -122,13 +124,6 @@ static int __proc_lnet_stats(void *data, int write,
 	return rc;
 }
 
-static int proc_lnet_stats(struct ctl_table *table, int write,
-			   void __user *buffer, size_t *lenp, loff_t *ppos)
-{
-	return lprocfs_call_handler(table->data, write, ppos, buffer, lenp,
-				    __proc_lnet_stats);
-}
-
 static int proc_lnet_routes(struct ctl_table *table, int write,
 			    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -562,9 +557,11 @@ static int proc_lnet_peers(struct ctl_table *table, int write,
 	return rc;
 }
 
-static int __proc_lnet_buffers(void *data, int write,
-			       loff_t pos, void __user *buffer, int nob)
+static int proc_lnet_buffers(struct ctl_table *table, int write,
+			     void __user *buffer, size_t *lenp, loff_t *ppos)
 {
+	size_t nob = *lenp;
+	loff_t pos = *ppos;
 	char *s;
 	char *tmpstr;
 	int tmpsiz;
@@ -620,13 +617,6 @@ static int __proc_lnet_buffers(void *data, int write,
 	return rc;
 }
 
-static int proc_lnet_buffers(struct ctl_table *table, int write,
-			     void __user *buffer, size_t *lenp, loff_t *ppos)
-{
-	return lprocfs_call_handler(table->data, write, ppos, buffer, lenp,
-				    __proc_lnet_buffers);
-}
-
 static int proc_lnet_nis(struct ctl_table *table, int write,
 			 void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -784,10 +774,13 @@ static struct lnet_portal_rotors	portal_rotors[] = {
 	},
 };
 
-static int __proc_lnet_portal_rotor(void *data, int write,
-				    loff_t pos, void __user *buffer, int nob)
+static int proc_lnet_portal_rotor(struct ctl_table *table, int write,
+				  void __user *buffer, size_t *lenp,
+				  loff_t *ppos)
 {
 	const int buf_len = 128;
+	size_t nob = *lenp;
+	loff_t pos = *ppos;
 	char *buf;
 	char *tmp;
 	int rc;
@@ -845,14 +838,6 @@ static int __proc_lnet_portal_rotor(void *data, int write,
 	return rc;
 }
 
-static int proc_lnet_portal_rotor(struct ctl_table *table, int write,
-				  void __user *buffer, size_t *lenp,
-				  loff_t *ppos)
-{
-	return lprocfs_call_handler(table->data, write, ppos, buffer, lenp,
-				    __proc_lnet_portal_rotor);
-}
-
 static struct ctl_table lnet_table[] = {
 	/*
 	 * NB No .strategy entries have been provided since sysctl(8) prefers