[PATCH] md: support write-mostly device in raid1

This allows a device in a raid1 to be marked as "write mostly".  Read requests
will only be sent if there is no other option.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 817062bf7352..7ef78e15ce04 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -181,6 +181,9 @@ struct mdk_rdev_s
         int faulty;                     /* if faulty do not issue IO requests */
         int in_sync;                    /* device is a full member of the array */
 
+        unsigned long   flags;          /* Should include faulty and in_sync here. */
+#define WriteMostly     4               /* Avoid reading if at all possible */
+
         int desc_nr;                    /* descriptor index in the superblock */
         int raid_disk;                  /* role of device in array */
         int saved_raid_disk;            /* role that device used to have in the