[PATCH] IO counters - per-partition part

	This chunk and the next one basically do equivalent of sard in the
right way - counters are exported per-disk in driverfs, as attributes of
disk or partition nodes.

drivers/block/ll_rw_blk.c

@@ -1777,12 +1777,24 @@ static int __make_request(request_queue_t *q, struct bio *bio)
 static inline void blk_partition_remap(struct bio *bio)
 {
 	struct block_device *bdev = bio->bi_bdev;
+	struct gendisk *disk = bdev->bd_disk;
+	struct hd_struct *p;
 	if (bdev == bdev->bd_contains)
 		return;
 
+	p = &disk->part[bdev->bd_dev-MKDEV(disk->major,disk->first_minor)-1];
+	switch (bio->bi_rw) {
+	case READ:
+		p->read_sectors += bio_sectors(bio);
+		p->reads++;
+		break;
+	case WRITE:
+		p->write_sectors += bio_sectors(bio);
+		p->writes++;
+		break;
+	}
 	bio->bi_sector += bdev->bd_offset;
 	bio->bi_bdev = bdev->bd_contains;
-	/* lots of checks are possible */
 }
 
 /**

fs/partitions/check.c

@@ -298,6 +298,14 @@ static ssize_t part_size_read(struct device *dev,
 	struct hd_struct *p = dev->driver_data;
 	return off ? 0 : sprintf(page, "%llu\n",(unsigned long long)p->nr_sects);
 }
+static ssize_t part_stat_read(struct device *dev,
+			char *page, size_t count, loff_t off)
+{
+	struct hd_struct *p = dev->driver_data;
+	return off ? 0 : sprintf(page, "%u %u %u %u\n",
+				p->reads, p->read_sectors,
+				p->writes, p->write_sectors);
+}
 static struct device_attribute part_attr_dev = {
 	.attr = {.name = "dev", .mode = S_IRUGO },
 	.show	= part_dev_read
@@ -310,6 +318,10 @@ static struct device_attribute part_attr_size = {
 	.attr = {.name = "size", .mode = S_IRUGO },
 	.show	= part_size_read
 };
+static struct device_attribute part_attr_stat = {
+	.attr = {.name = "stat", .mode = S_IRUGO },
+	.show	= part_stat_read
+};
 
 void delete_partition(struct gendisk *disk, int part)
 {
@@ -319,10 +331,12 @@ void delete_partition(struct gendisk *disk, int part)
 		return;
 	p->start_sect = 0;
 	p->nr_sects = 0;
+	p->reads = p->writes = p->read_sectors = p->write_sectors = 0;
 	devfs_unregister(p->de);
 	dev = p->hd_driverfs_dev;
 	p->hd_driverfs_dev = NULL;
 	if (dev) {
+		device_remove_file(dev, &part_attr_stat);
 		device_remove_file(dev, &part_attr_size);
 		device_remove_file(dev, &part_attr_start);
 		device_remove_file(dev, &part_attr_dev);
@@ -356,6 +370,7 @@ void add_partition(struct gendisk *disk, int part, sector_t start, sector_t len)
 	device_create_file(dev, &part_attr_dev);
 	device_create_file(dev, &part_attr_start);
 	device_create_file(dev, &part_attr_size);
+	device_create_file(dev, &part_attr_stat);
 	p->hd_driverfs_dev = dev;
 }
 

include/linux/genhd.h

@@ -63,6 +63,7 @@ struct hd_struct {
 	sector_t nr_sects;
 	devfs_handle_t de;              /* primary (master) devfs entry  */
 	struct device *hd_driverfs_dev;  /* support driverfs hiearchy     */
+	unsigned reads, read_sectors, writes, write_sectors;
 	int policy;
 };