[Xen-devel] [PATCH] xen-blkfront: properly name all devices

["Jan Beulich" <JBeulich@xxxxxxxx>]

- 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@xxxxxxxx>

---
 drivers/block/xen-blkfront.c |   40 ++++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 18 deletions(-)

--- 3.4-rc1/drivers/block/xen-blkfront.c
+++ 3.4-rc1-xen-blkfront-all-devices/drivers/block/xen-blkfront.c
@@ -528,6 +528,14 @@ static int xen_translate_vdev(int vdevic
        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)
@@ -538,6 +546,7 @@ static int xlvbd_alloc_gendisk(blkif_sec
        unsigned int offset;
        int minor;
        int nr_parts;
+       char *ptr;
 
        BUG_ON(info->gd != NULL);
        BUG_ON(info->rq != NULL);
@@ -562,7 +571,11 @@ static int xlvbd_alloc_gendisk(blkif_sec
                                        "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;
@@ -576,23 +589,14 @@ static int xlvbd_alloc_gendisk(blkif_sec
        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;




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