MD: add a new disk role to present write journal device

Next patches will use a disk as raid5/6 journaling. We need a new disk
role to present the journal device and add MD_FEATURE_JOURNAL to
feature_map for backward compability.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/uapi/linux/raid/md_p.h b/include/uapi/linux/raid/md_p.h
index d1fc8a637368..eaaab52077a3 100644
--- a/include/uapi/linux/raid/md_p.h
+++ b/include/uapi/linux/raid/md_p.h
@@ -89,9 +89,11 @@
                                    * read requests will only be sent here in
                                    * dire need
                                    */
+#define MD_DISK_JOURNAL         18 /* disk is used as the write journal in RAID-5/6 */
 
 #define MD_DISK_ROLE_SPARE      0xffff
 #define MD_DISK_ROLE_FAULTY     0xfffe
+#define MD_DISK_ROLE_JOURNAL    0xfffd
 #define MD_DISK_ROLE_MAX        0xff00 /* max value of regular disk role */
 
 typedef struct mdp_device_descriptor_s {
@@ -307,6 +309,7 @@ struct mdp_superblock_1 {
                                              * is guided by bitmap.
                                              */
 #define MD_FEATURE_CLUSTERED            256 /* clustered MD */
+#define MD_FEATURE_JOURNAL              512 /* support write cache */
 #define MD_FEATURE_ALL                  (MD_FEATURE_BITMAP_OFFSET       \
                                         |MD_FEATURE_RECOVERY_OFFSET     \
                                         |MD_FEATURE_RESHAPE_ACTIVE      \