Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

Pull virtio fixes from Michael S. Tsirkin:
 "Here are some virtio fixes for 3.4: a test build fix, a patch by Ren
  fixing naming for systems with a massive number of virtio blk devices,
  and balloon fixes for powerpc by David Gibson.

  There was some discussion about Ren's patch for virtio disc naming:
  some people wanted to move the legacy name mangling function to the
  block core.  But there's no concensus on that yet, and we can always
  deduplicate later.  Added comments in the hope that this will stop
  people from copying this legacy naming scheme into future drivers."

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  virtio_balloon: fix handling of PAGE_SIZE != 4k
  virtio_balloon: Fix endian bug
  virtio_blk: helper function to format disk names
  tools/virtio: fix up vhost/test module build

1 files changed, 29 insertions, 12 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 0e4ef3d..0d39f2f 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -375,6 +375,34 @@ static int init_vq(struct virtio_blk *vblk)
 	return err;
 }
 
+/*
+ * Legacy naming scheme used for virtio devices.  We are stuck with it for
+ * virtio blk but don't ever use it for any new driver.
+ */
+static int virtblk_name_format(char *prefix, int index, char *buf, int buflen)
+{
+	const int base = 'z' - 'a' + 1;
+	char *begin = buf + strlen(prefix);
+	char *end = buf + buflen;
+	char *p;
+	int unit;
+
+	p = end - 1;
+	*p = '\0';
+	unit = base;
+	do {
+		if (p == begin)
+			return -EINVAL;
+		*--p = 'a' + (index % unit);
+		index = (index / unit) - 1;
+	} while (index >= 0);
+
+	memmove(begin, p, end - p);
+	memcpy(buf, prefix, strlen(prefix));
+
+	return 0;
+}
+
 static int __devinit virtblk_probe(struct virtio_device *vdev)
 {
 	struct virtio_blk *vblk;
@@ -443,18 +471,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
 
 	q->queuedata = vblk;
 
-	if (index < 26) {
-		sprintf(vblk->disk->disk_name, "vd%c", 'a' + index % 26);
-	} else if (index < (26 + 1) * 26) {
-		sprintf(vblk->disk->disk_name, "vd%c%c",
-			'a' + index / 26 - 1, 'a' + index % 26);
-	} else {
-		const unsigned int m1 = (index / 26 - 1) / 26 - 1;
-		const unsigned int m2 = (index / 26 - 1) % 26;
-		const unsigned int m3 =  index % 26;
-		sprintf(vblk->disk->disk_name, "vd%c%c%c",
-			'a' + m1, 'a' + m2, 'a' + m3);
-	}
+	virtblk_name_format("vd", index, vblk->disk->disk_name, DISK_NAME_LEN);
 
 	vblk->disk->major = major;
 	vblk->disk->first_minor = index_to_minor(index);