xen-blkfront: properly name all devices

- devices beyond xvdzz didn't get proper names assigned at all
- extended devices with minors not representable within the kernel's
  major/minor bit split spilled into foreign majors

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 22 insertions, 18 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 4e86393a09cf..4f2b46052976 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -526,6 +526,14 @@ static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
         return 0;
 }
 
+static char *encode_disk_name(char *ptr, unsigned int n)
+{
+        if (n >= 26)
+                ptr = encode_disk_name(ptr, n / 26 - 1);
+        *ptr = 'a' + n % 26;
+        return ptr + 1;
+}
+
 static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
                                struct blkfront_info *info,
                                u16 vdisk_info, u16 sector_size)
@@ -536,6 +544,7 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
         unsigned int offset;
         int minor;
         int nr_parts;
+        char *ptr;
 
         BUG_ON(info->gd != NULL);
         BUG_ON(info->rq != NULL);
@@ -560,7 +569,11 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
                                         "emulated IDE disks,\n\t choose an xvd device name"
                                         "from xvde on\n", info->vdevice);
         }
-        err = -ENODEV;
+        if (minor >> MINORBITS) {
+                pr_warn("blkfront: %#x's minor (%#x) out of range; ignoring\n",
+                        info->vdevice, minor);
+                return -ENODEV;
+        }
 
         if ((minor % nr_parts) == 0)
                 nr_minors = nr_parts;
@@ -574,23 +587,14 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
         if (gd == NULL)
                 goto release;
 
-        if (nr_minors > 1) {
-                if (offset < 26)
-                        sprintf(gd->disk_name, "%s%c", DEV_NAME, 'a' + offset);
-                else
-                        sprintf(gd->disk_name, "%s%c%c", DEV_NAME,
-                                'a' + ((offset / 26)-1), 'a' + (offset % 26));
-        } else {
-                if (offset < 26)
-                        sprintf(gd->disk_name, "%s%c%d", DEV_NAME,
-                                'a' + offset,
-                                minor & (nr_parts - 1));
-                else
-                        sprintf(gd->disk_name, "%s%c%c%d", DEV_NAME,
-                                'a' + ((offset / 26) - 1),
-                                'a' + (offset % 26),
-                                minor & (nr_parts - 1));
-        }
+        strcpy(gd->disk_name, DEV_NAME);
+        ptr = encode_disk_name(gd->disk_name + sizeof(DEV_NAME) - 1, offset);
+        BUG_ON(ptr >= gd->disk_name + DISK_NAME_LEN);
+        if (nr_minors > 1)
+                *ptr = 0;
+        else
+                snprintf(ptr, gd->disk_name + DISK_NAME_LEN - ptr,
+                         "%d", minor & (nr_parts - 1));
 
         gd->major = XENVBD_MAJOR;
         gd->first_minor = minor;