[PATCH] md: replace magic numbers in sb_dirty with well defined bit flags

Instead of magic numbers (0,1,2,3) in sb_dirty, we have
some flags instead:
MD_CHANGE_DEVS
   Some device state has changed requiring superblock update
   on all devices.
MD_CHANGE_CLEAN
   The array has transitions from 'clean' to 'dirty' or back,
   requiring a superblock update on active devices, but possibly
   not on spares
MD_CHANGE_PENDING
   A superblock update is underway.

We wait for an update to complete by waiting for all flags to be clear.  A
flag can be set at any time, even during an update, without risk that the
change will be lost.

Stop exporting md_update_sb - isn't needed.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/raid/md.h b/include/linux/raid/md.h
index c588709acbbc..866a1e2b0ce0 100644
--- a/include/linux/raid/md.h
+++ b/include/linux/raid/md.h
@@ -95,7 +95,6 @@ extern int sync_page_io(struct block_device *bdev, sector_t sector, int size,
 extern void md_do_sync(mddev_t *mddev);
 extern void md_new_event(mddev_t *mddev);
 
-extern void md_update_sb(mddev_t * mddev);
 
 #endif /* CONFIG_MD */
 #endif 
diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 920b94fe31fa..e423dad1a7fd 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -116,7 +116,11 @@ struct mddev_s
         dev_t                           unit;
         int                             md_minor;
         struct list_head                disks;
-        int                             sb_dirty;
+        unsigned long                   flags;
+#define MD_CHANGE_DEVS  0       /* Some device status has changed */
+#define MD_CHANGE_CLEAN 1       /* transition to or from 'clean' */
+#define MD_CHANGE_PENDING 2     /* superblock update in progress */
+
         int                             ro;
 
         struct gendisk                  *gendisk;