md/bitmap: prepare for storing write-intent-bitmap via dm-dirty-log.
This allows md/raid5 to fully work as a dm target.
Normally md uses a 'filemap' which contains a list of pages of bits
each of which may be written separately.
dm-log uses and all-or-nothing approach to writing the log, so
when using a dm-log, ->filemap is NULL and the flags normally stored
in filemap_attr are stored in ->logattrs instead.
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 0a85078..cccbadb 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -317,6 +317,11 @@
* hot-adding a bitmap. It should
* eventually be settable by sysfs.
*/
+ /* When md is serving under dm, it might use a
+ * dirty_log to store the bits.
+ */
+ struct dm_dirty_log *log;
+
struct mutex mutex;
unsigned long chunksize;
unsigned long daemon_sleep; /* how many jiffies between updates? */