block: fix partition info printouts

Recent block_class iteration updates 5c6f35c5..27f30251 broke partition
info printouts.

* printk_all_partitions(): Partition print out stops when it meets a
  partition hole.  Partition printing inner loop should continue
  instead of exiting on empty partition slot.

* /proc/partitions and /proc/diskstats: If all information can't be
  read in single read(), the information is truncated.  This is
  because find_start() doesn't actually update the counter containing
  the initial seek.  It runs to the end and ends up always reporting
  EOF on the second read.

This patch fixes both problems.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/genhd.c

@@ -236,7 +236,7 @@ static int printk_partition(struct device *dev, void *data)
 	int n;
 
 	if (dev->type != &disk_type)
-		goto exit;
+		return 0;
 
 	sgp = dev_to_disk(dev);
 	/*
@@ -244,7 +244,7 @@ static int printk_partition(struct device *dev, void *data)
 	 */
 	if (get_capacity(sgp) == 0 ||
 	    (sgp->flags & GENHD_FL_SUPPRESS_PARTITION_INFO))
-		goto exit;
+		return 0;
 
 	/*
 	 * Note, unlike /proc/partitions, I am showing the numbers in
@@ -264,15 +264,15 @@ static int printk_partition(struct device *dev, void *data)
 	/* now show the partitions */
 	for (n = 0; n < sgp->minors - 1; ++n) {
 		if (sgp->part[n] == NULL)
-			goto exit;
+			continue;
 		if (sgp->part[n]->nr_sects == 0)
-			goto exit;
+			continue;
 		printk("  %02x%02x %10llu %s\n",
 			sgp->major, n + 1 + sgp->first_minor,
 			(unsigned long long)sgp->part[n]->nr_sects >> 1,
 			disk_name(sgp, n + 1, buf));
 	}
-exit:
+
 	return 0;
 }