2 files changed, 76 insertions, 3 deletions

diff --git a/init/Kconfig b/init/Kconfig
index be85a0ab1b82..bd125a795374 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -661,11 +661,14 @@ config BLK_CGROUP
 
         Currently, CFQ IO scheduler uses it to recognize task groups and
         control disk bandwidth allocation (proportional time slice allocation)
-        to such task groups.
+        to such task groups. It is also used by bio throttling logic in
+        block layer to implement upper limit in IO rates on a device.
 
         This option only enables generic Block IO controller infrastructure.
-        One needs to also enable actual IO controlling logic in CFQ for it
-        to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
+        One needs to also enable actual IO controlling logic/policy. For
+        enabling proportional weight division of disk bandwidth in CFQ seti
+        CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
+        CONFIG_BLK_THROTTLE=y.
 
         See Documentation/cgroups/blkio-controller.txt for more information.
 
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 02e3ca4fc527..42db0551c3aa 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -58,6 +58,62 @@ static int __init readwrite(char *str)
 __setup("ro", readonly);
 __setup("rw", readwrite);
 
+#ifdef CONFIG_BLOCK
+/**
+ * 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 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;
+}
+#endif
+
 /*
  *      Convert a name into device number.  We accept the following variants:
  *
@@ -68,6 +124,8 @@ __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 +140,18 @@ dev_t name_to_dev_t(char *name)
         dev_t res = 0;
         int part;
 
+#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;
+                goto done;
+        }
+#endif
+
         if (strncmp(name, "/dev/", 5) != 0) {
                 unsigned maj, min;