dm raid1: add is_remote_recovering hook for clusters
The logging API needs an extra function to make cluster mirroring
possible. This new function allows us to check whether a mirror
region is being recovered on another machine in the cluster. This
helps us prevent simultaneous recovery I/O and process I/O to the
same locations on disk.
Cluster-aware log modules will implement this function. Single
machine log modules will not. So, there is no performance
penalty for single machine mirrors.
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Acked-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/include/linux/dm-dirty-log.h b/include/linux/dm-dirty-log.h
index 727602b..5e8b11d 100644
--- a/include/linux/dm-dirty-log.h
+++ b/include/linux/dm-dirty-log.h
@@ -116,6 +116,16 @@
*/
int (*status)(struct dm_dirty_log *log, status_type_t status_type,
char *result, unsigned maxlen);
+
+ /*
+ * is_remote_recovering is necessary for cluster mirroring. It provides
+ * a way to detect recovery on another node, so we aren't writing
+ * concurrently. This function is likely to block (when a cluster log
+ * is used).
+ *
+ * Returns: 0, 1
+ */
+ int (*is_remote_recovering)(struct dm_dirty_log *log, region_t region);
};
int dm_dirty_log_type_register(struct dm_dirty_log_type *type);