Add new disk to clustered array

Algorithm:
1. Node 1 issues mdadm --manage /dev/mdX --add /dev/sdYY which issues
   ioctl(ADD_NEW_DISC with disc.state set to MD_DISK_CLUSTER_ADD)
2. Node 1 sends NEWDISK with uuid and slot number
3. Other nodes issue kobject_uevent_env with uuid and slot number
(Steps 4,5 could be a udev rule)
4. In userspace, the node searches for the disk, perhaps
   using blkid -t SUB_UUID=""
5. Other nodes issue either of the following depending on whether the disk
   was found:
   ioctl(ADD_NEW_DISK with disc.state set to MD_DISK_CANDIDATE and
	 disc.number set to slot number)
   ioctl(CLUSTERED_DISK_NACK)
6. Other nodes drop lock on no-new-devs (CR) if device is found
7. Node 1 attempts EX lock on no-new-devs
8. If node 1 gets the lock, it sends METADATA_UPDATED after unmarking the disk
   as SpareLocal
9. If not (get no-new-dev lock), it fails the operation and sends METADATA_UPDATED
10. Other nodes understand if the device is added or not by reading the superblock again after receiving the METADATA_UPDATED message.

Signed-off-by: Lidong Zhong <lzhong@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

2 files changed, 7 insertions, 0 deletions

diff --git a/include/uapi/linux/raid/md_p.h b/include/uapi/linux/raid/md_p.h
index 643489d33e68..2ae6131e69a5 100644
--- a/include/uapi/linux/raid/md_p.h
+++ b/include/uapi/linux/raid/md_p.h
@@ -78,6 +78,12 @@
 #define MD_DISK_ACTIVE          1 /* disk is running or spare disk */
 #define MD_DISK_SYNC            2 /* disk is in sync with the raid set */
 #define MD_DISK_REMOVED         3 /* disk is in sync with the raid set */
+#define MD_DISK_CLUSTER_ADD     4 /* Initiate a disk add across the cluster
+                                   * For clustered enviroments only.
+                                   */
+#define MD_DISK_CANDIDATE       5 /* disk is added as spare (local) until confirmed
+                                   * For clustered enviroments only.
+                                   */
 
 #define MD_DISK_WRITEMOSTLY     9 /* disk is "write-mostly" is RAID1 config.
                                    * read requests will only be sent here in
diff --git a/include/uapi/linux/raid/md_u.h b/include/uapi/linux/raid/md_u.h
index 74e7c60c4716..1cb8aa6850b5 100644
--- a/include/uapi/linux/raid/md_u.h
+++ b/include/uapi/linux/raid/md_u.h
@@ -62,6 +62,7 @@
 #define STOP_ARRAY              _IO (MD_MAJOR, 0x32)
 #define STOP_ARRAY_RO           _IO (MD_MAJOR, 0x33)
 #define RESTART_ARRAY_RW        _IO (MD_MAJOR, 0x34)
+#define CLUSTERED_DISK_NACK     _IO (MD_MAJOR, 0x35)
 
 /* 63 partitions with the alternate major number (mdp) */
 #define MdpMinorShift 6