From: Chris Lalancette <clalance@redhat.com>
Date: Thu, 17 Jul 2008 17:28:08 +0200
Subject: [xen] blktap: add statistics
Message-id: 487F6508.8080103@redhat.com
O-Subject: [RHEL5.3 PATCH 2/7]: Add blktap statistics v2
Bugzilla: 250104
RH-Acked-by: Stephen Tweedie <sct@redhat.com>
RH-Acked-by: Bill Burns <bburns@redhat.com>
RH-Acked-by: Don Dutile <ddutile@redhat.com>

The heart of the patch series, that actually adds in the statistics for blktap
and extends the statistics for blkback to include the number of sectors
read/wrote.  From xen-3.1-testing.hg c/s 14040

diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
index 3d5914c..12378bd 100644
--- a/drivers/xen/blkback/blkback.c
+++ b/drivers/xen/blkback/blkback.c
@@ -468,6 +468,12 @@ static void dispatch_rw_block_io(blkif_t *blkif,
 	for (i = 0; i < nbio; i++)
 		submit_bio(operation, biolist[i]);
 
+        if (operation == READ) {
+                blkif->st_rd_sect += preq.nr_sects;
+        } else if (operation == WRITE) {
+                blkif->st_wr_sect += preq.nr_sects;
+        }
+
 	return;
 
  fail_put_bio:
diff --git a/drivers/xen/blkback/common.h b/drivers/xen/blkback/common.h
index a5ee16a..785e482 100644
--- a/drivers/xen/blkback/common.h
+++ b/drivers/xen/blkback/common.h
@@ -86,6 +86,8 @@ typedef struct blkif_st {
 	int                 st_rd_req;
 	int                 st_wr_req;
 	int                 st_oo_req;
+	int                 st_rd_sect;
+	int                 st_wr_sect;
 
 	wait_queue_head_t waiting_to_free;
 
diff --git a/drivers/xen/blkback/xenbus.c b/drivers/xen/blkback/xenbus.c
index 05a8bb1..ddb77de 100644
--- a/drivers/xen/blkback/xenbus.c
+++ b/drivers/xen/blkback/xenbus.c
@@ -112,14 +112,18 @@ static void update_blkif_status(blkif_t *blkif)
 	}								\
 	DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 
-VBD_SHOW(oo_req, "%d\n", be->blkif->st_oo_req);
-VBD_SHOW(rd_req, "%d\n", be->blkif->st_rd_req);
-VBD_SHOW(wr_req, "%d\n", be->blkif->st_wr_req);
+VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
+VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
+VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
+VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
+VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 
 static struct attribute *vbdstat_attrs[] = {
 	&dev_attr_oo_req.attr,
 	&dev_attr_rd_req.attr,
 	&dev_attr_wr_req.attr,
+	&dev_attr_rd_sect.attr,
+	&dev_attr_wr_sect.attr,
 	NULL
 };
 
diff --git a/drivers/xen/blktap/blktapmain.c b/drivers/xen/blktap/blktapmain.c
index 5adf488..6d377e8 100644
--- a/drivers/xen/blktap/blktapmain.c
+++ b/drivers/xen/blktap/blktapmain.c
@@ -1151,7 +1151,7 @@ static void dispatch_rw_block_io(blkif_t *blkif,
 	int op, operation = (req->operation == BLKIF_OP_WRITE) ? WRITE : READ;
 	struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST*2];
 	unsigned int nseg;
-	int ret, i;
+	int ret, i, nr_sects = 0;
 	tap_blkif_t *info = tapfds[blkif->dev_num];
 	
 	blkif_request_t *target;
@@ -1226,6 +1226,9 @@ static void dispatch_rw_block_io(blkif_t *blkif,
 					  req->seg[i].gref, blkif->domid);
 			op++;
 		}
+
+		nr_sects += (req->seg[i].last_sect - 
+			     req->seg[i].first_sect + 1);
 	}
 
 	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map, op);
@@ -1347,6 +1350,13 @@ static void dispatch_rw_block_io(blkif_t *blkif,
 	target->id = usr_idx;
 	wmb(); /* blktap_poll() reads req_prod_pvt asynchronously */
 	info->ufe_ring.req_prod_pvt++;
+
+	if (operation == READ) {
+		blkif->st_rd_sect += nr_sects;
+	} else if (operation == WRITE) {
+		blkif->st_wr_sect += nr_sects;
+	}
+
 	return;
 
  fail_flush:
diff --git a/drivers/xen/blktap/common.h b/drivers/xen/blktap/common.h
index 561058a..222c50b 100644
--- a/drivers/xen/blktap/common.h
+++ b/drivers/xen/blktap/common.h
@@ -76,6 +76,8 @@ typedef struct blkif_st {
 	int                 st_rd_req;
 	int                 st_wr_req;
 	int                 st_oo_req;
+	int                 st_rd_sect;
+	int                 st_wr_sect;
 
 	wait_queue_head_t waiting_to_free;
 
diff --git a/drivers/xen/blktap/xenbus.c b/drivers/xen/blktap/xenbus.c
index 58a79e7..526ce05 100644
--- a/drivers/xen/blktap/xenbus.c
+++ b/drivers/xen/blktap/xenbus.c
@@ -112,6 +112,74 @@ static int blktap_name(blkif_t *blkif, char *buf)
 	return 0;
 }
 
+/****************************************************************
+ *  sysfs interface for VBD I/O requests
+ */
+
+#define VBD_SHOW(name, format, args...)					\
+	static ssize_t show_##name(struct device *_dev,			\
+				   struct device_attribute *attr,	\
+				   char *buf)				\
+	{								\
+		struct xenbus_device *dev = to_xenbus_device(_dev);	\
+		struct backend_info *be = dev->dev.driver_data;		\
+									\
+		return sprintf(buf, format, ##args);			\
+	}								\
+	DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
+
+VBD_SHOW(tap_oo_req,  "%d\n", be->blkif->st_oo_req);
+VBD_SHOW(tap_rd_req,  "%d\n", be->blkif->st_rd_req);
+VBD_SHOW(tap_wr_req,  "%d\n", be->blkif->st_wr_req);
+VBD_SHOW(tap_rd_sect, "%d\n", be->blkif->st_rd_sect);
+VBD_SHOW(tap_wr_sect, "%d\n", be->blkif->st_wr_sect);
+
+static struct attribute *tapstat_attrs[] = {
+	&dev_attr_tap_oo_req.attr,
+	&dev_attr_tap_rd_req.attr,
+	&dev_attr_tap_wr_req.attr,
+	&dev_attr_tap_rd_sect.attr,
+	&dev_attr_tap_wr_sect.attr,
+	NULL
+};
+
+static struct attribute_group tapstat_group = {
+	.name = "statistics",
+	.attrs = tapstat_attrs,
+};
+
+int xentap_sysfs_addif(struct xenbus_device *dev)
+{
+	return sysfs_create_group(&dev->dev.kobj, &tapstat_group);
+}
+
+void xentap_sysfs_delif(struct xenbus_device *dev)
+{
+	sysfs_remove_group(&dev->dev.kobj, &tapstat_group);
+}
+
+static int blktap_remove(struct xenbus_device *dev)
+{
+	struct backend_info *be = dev->dev.driver_data;
+
+	if (be->backend_watch.node) {
+		unregister_xenbus_watch(&be->backend_watch);
+		kfree(be->backend_watch.node);
+		be->backend_watch.node = NULL;
+	}
+	if (be->blkif) {
+		if (be->blkif->xenblkd)
+			kthread_stop(be->blkif->xenblkd);
+		signal_tapdisk(be->blkif->dev_num);
+		tap_blkif_free(be->blkif);
+		be->blkif = NULL;
+	}
+	xentap_sysfs_delif(be->dev);
+	kfree(be);
+	dev->dev.driver_data = NULL;
+	return 0;
+}
+
 static void tap_update_blkif_status(blkif_t *blkif)
 { 
 	int err;
@@ -137,6 +205,13 @@ static void tap_update_blkif_status(blkif_t *blkif)
 		return;
 	}
 
+	err = xentap_sysfs_addif(blkif->be->dev);
+	if (err) {
+		xenbus_dev_fatal(blkif->be->dev, err, 
+				 "creating sysfs entries");
+		return;
+	}
+
 	blkif->xenblkd = kthread_run(tap_blkif_schedule, blkif, name);
 	if (IS_ERR(blkif->xenblkd)) {
 		err = PTR_ERR(blkif->xenblkd);
@@ -146,27 +221,6 @@ static void tap_update_blkif_status(blkif_t *blkif)
 	}
 }
 
-static int blktap_remove(struct xenbus_device *dev)
-{
-	struct backend_info *be = dev->dev.driver_data;
-
-	if (be->backend_watch.node) {
-		unregister_xenbus_watch(&be->backend_watch);
-		kfree(be->backend_watch.node);
-		be->backend_watch.node = NULL;
-	}
-	if (be->blkif) {
-		if (be->blkif->xenblkd)
-			kthread_stop(be->blkif->xenblkd);
-		signal_tapdisk(be->blkif->dev_num);
-		tap_blkif_free(be->blkif);
-		be->blkif = NULL;
-	}
-	kfree(be);
-	dev->dev.driver_data = NULL;
-	return 0;
-}
-
 /**
  * Entry point to this code when a new device is created.  Allocate
  * the basic structures, and watch the store waiting for the