From c0aa3e0916d7e531e69b02e426f7162dfb1c6c0f Mon Sep 17 00:00:00 2001 From: Ren Mingxin Date: Tue, 10 Apr 2012 15:28:05 +0800 Subject: [PATCH] virtio_blk: helper function to format disk names The current virtio block's naming algorithm just supports 18278 (26^3 + 26^2 + 26) disks. If there are more virtio blocks, there will be disks with the same name. Based on commit 3e1a7ff8a0a7b948f2684930166954f9e8e776fe, add a function "virtblk_name_format()" for virtio block to support mass of disks naming. Notes: - Our naming scheme is ugly. We are stuck with it for virtio but don't use it for any new driver: new drivers should name their devices PREFIX%d where the sequence number can be allocated by ida - sd_format_disk_name has exactly the same logic. Moving it to a central place was deferred over worries that this will make people keep using the legacy naming in new drivers. We kept code idential in case someone wants to deduplicate later. Signed-off-by: Ren Mingxin Acked-by: Asias He Signed-off-by: Michael S. Tsirkin --- drivers/block/virtio_blk.c | 41 +++++++++++++++++++++++++++----------- 1 file changed, 29 insertions(+), 12 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index c4a60badf252..303779cb1fa2 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -374,6 +374,34 @@ 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; @@ -442,18 +470,7 @@ 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); -- GitLab