init: add support for root devices specified by partition UUID

[linux-flexiantxendom0-3.2.10.git] / init / do_mounts.c

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 02e3ca4..804f9c6 100644 (file)
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -58,6 +58,60 @@ static int __init readwrite(char *str)
 __setup("ro", readonly);
 __setup("rw", readwrite);
 
+/**
+ * match_dev_by_uuid - callback for finding a partition using its uuid
+ * @dev:       device passed in by the caller
+ * @data:      opaque pointer to a 36 byte char array with a UUID
+ *
+ * Returns 1 if the device matches, and 0 otherwise.
+ */
+static int __init match_dev_by_uuid(struct device *dev, void *data)
+{
+       u8 *uuid = data;
+       struct hd_struct *part = dev_to_part(dev);
+
+       if (!part->info)
+               goto no_match;
+
+       if (memcmp(uuid, part->info->uuid, sizeof(part->info->uuid)))
+                       goto no_match;
+
+       return 1;
+no_match:
+       return 0;
+}
+
+
+/**
+ * devt_from_partuuid - looks up the dev_t of a partition by its UUID
+ * @uuid:      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.
+ *
+ * Returns the matching dev_t on success or 0 on failure.
+ */
+static dev_t __init devt_from_partuuid(char *uuid_str)
+{
+       dev_t res = 0;
+       struct device *dev = NULL;
+       u8 uuid[16];
+
+       /* Pack the requested UUID in the expected format. */
+       part_pack_uuid(uuid_str, uuid);
+
+       dev = class_find_device(&block_class, NULL, uuid, &match_dev_by_uuid);
+       if (!dev)
+               goto done;
+
+       res = dev->devt;
+       put_device(dev);
+
+done:
+       return res;
+}
+
 /*
  *     Convert a name into device number.  We accept the following variants:
  *
@@ -68,6 +122,8 @@ __setup("rw", readwrite);
  *         of partition - device number of disk plus the partition number
  *     5) /dev/<disk_name>p<decimal> - same as the above, that form is
  *        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.
  *
  *     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
@@ -82,6 +138,16 @@ dev_t name_to_dev_t(char *name)
        dev_t res = 0;
        int part;
 
+       if (strncmp(name, "PARTUUID=", 9) == 0) {
+               name += 9;
+               if (strlen(name) != 36)
+                       goto fail;
+               res = devt_from_partuuid(name);
+               if (!res)
+                       goto fail;
+               goto done;
+       }
+
        if (strncmp(name, "/dev/", 5) != 0) {
                unsigned maj, min;