1 files changed, 43 insertions, 5 deletions

diff --git a/init/do_mounts.c b/init/do_mounts.c
index c0851a8e030c..0f6e1d985a3b 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -28,7 +28,7 @@ int __initdata rd_doload;	/* 1 = load RAM disk, 0 = don't load */
 int root_mountflags = MS_RDONLY | MS_SILENT;
 static char * __initdata root_device_name;
 static char __initdata saved_root_name[64];
-static int __initdata root_wait;
+static int root_wait;
 
 dev_t ROOT_DEV;
 
@@ -85,12 +85,15 @@ no_match:
 
 /**
  * devt_from_partuuid - looks up the dev_t of a partition by its UUID
- * @uuid:       36 byte char array containing a hex ascii UUID
+ * @uuid:       min 36 byte char array containing a hex ascii UUID
  *
  * The function will return the first partition which contains a matching
  * UUID value in its partition_meta_info struct.  This does not search
  * by filesystem UUIDs.
  *
+ * If @uuid is followed by a "/PARTNROFF=%d", then the number will be
+ * extracted and used as an offset from the partition identified by the UUID.
+ *
  * Returns the matching dev_t on success or 0 on failure.
  */
 static dev_t devt_from_partuuid(char *uuid_str)
@@ -98,6 +101,28 @@ static dev_t devt_from_partuuid(char *uuid_str)
         dev_t res = 0;
         struct device *dev = NULL;
         u8 uuid[16];
+        struct gendisk *disk;
+        struct hd_struct *part;
+        int offset = 0;
+
+        if (strlen(uuid_str) < 36)
+                goto done;
+
+        /* Check for optional partition number offset attributes. */
+        if (uuid_str[36]) {
+                char c = 0;
+                /* Explicitly fail on poor PARTUUID syntax. */
+                if (sscanf(&uuid_str[36],
+                           "/PARTNROFF=%d%c", &offset, &c) != 1) {
+                        printk(KERN_ERR "VFS: PARTUUID= is invalid.\n"
+                         "Expected PARTUUID=<valid-uuid-id>[/PARTNROFF=%%d]\n");
+                        if (root_wait)
+                                printk(KERN_ERR
+                                     "Disabling rootwait; root= is invalid.\n");
+                        root_wait = 0;
+                        goto done;
+                }
+        }
 
         /* Pack the requested UUID in the expected format. */
         part_pack_uuid(uuid_str, uuid);
@@ -107,8 +132,21 @@ static dev_t devt_from_partuuid(char *uuid_str)
                 goto done;
 
         res = dev->devt;
-        put_device(dev);
 
+        /* Attempt to find the partition by offset. */
+        if (!offset)
+                goto no_offset;
+
+        res = 0;
+        disk = part_to_disk(dev_to_part(dev));
+        part = disk_get_part(disk, dev_to_part(dev)->partno + offset);
+        if (part) {
+                res = part_devt(part);
+                put_device(part_to_dev(part));
+        }
+
+no_offset:
+        put_device(dev);
 done:
         return res;
 }
@@ -126,6 +164,8 @@ done:
  *         used when disk name of partitioned disk ends on a digit.
  *      6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
  *         unique id of a partition if the partition table provides it.
+ *      7) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
+ *         a partition with a known unique id.
  *
  *      If name doesn't have fall into the categories above, we return (0,0).
  *      block_class is used to check if something is a disk name. If the disk
@@ -143,8 +183,6 @@ dev_t name_to_dev_t(char *name)
 #ifdef CONFIG_BLOCK
         if (strncmp(name, "PARTUUID=", 9) == 0) {
                 name += 9;
-                if (strlen(name) != 36)
-                        goto fail;
                 res = devt_from_partuuid(name);
                 if (!res)
                         goto fail;