md: override md superblock recovery_offset for journal device

Journal device stores data in a log structure. We need record the log
start. Here we override md superblock recovery_offset for this purpose.
This field of a journal device is meaningless otherwise.

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

1 files changed, 4 insertions, 1 deletions

diff --git a/include/uapi/linux/raid/md_p.h b/include/uapi/linux/raid/md_p.h
index eaaab52077a3..a5f54ff26c20 100644
--- a/include/uapi/linux/raid/md_p.h
+++ b/include/uapi/linux/raid/md_p.h
@@ -258,7 +258,10 @@ struct mdp_superblock_1 {
         __le64  data_offset;    /* sector start of data, often 0 */
         __le64  data_size;      /* sectors in this device that can be used for data */
         __le64  super_offset;   /* sector start of this superblock */
-        __le64  recovery_offset;/* sectors before this offset (from data_offset) have been recovered */
+        union {
+                __le64  recovery_offset;/* sectors before this offset (from data_offset) have been recovered */
+                __le64  journal_tail;/* journal tail of journal device (from data_offset) */
+        };
         __le32  dev_number;     /* permanent identifier of this  device - not role in raid */
         __le32  cnt_corrected_read; /* number of read errors that were corrected by re-writing */
         __u8    device_uuid[16]; /* user-space setable, ignored by kernel */