md: add raid4/5/6 journal mode switching API
Commit 2ded370373a4 ("md/r5cache: State machine for raid5-cache write
back mode") added support for "write-back" caching on the raid journal
device.
In order to allow the dm-raid target to switch between the available
"write-through" and "write-back" modes, provide a new
r5c_journal_mode_set() API.
Use the new API in existing r5c_journal_mode_store()
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Acked-by: Shaohua Li <shli@fb.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 4bb27b9..ec8ca15 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -547,6 +547,16 @@
int stripes_cnt;
};
+/*
+ * r5c journal modes of the array: write-back or write-through.
+ * write-through mode has identical behavior as existing log only
+ * implementation.
+ */
+enum r5c_journal_mode {
+ R5C_JOURNAL_MODE_WRITE_THROUGH = 0,
+ R5C_JOURNAL_MODE_WRITE_BACK = 1,
+};
+
enum r5_cache_state {
R5_INACTIVE_BLOCKED, /* release of inactive stripes blocked,
* waiting for 25% to be free
@@ -795,4 +805,5 @@
extern struct md_sysfs_entry r5c_journal_mode;
extern void r5c_update_on_rdev_error(struct mddev *mddev);
extern bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect);
+extern int r5c_journal_mode_set(struct mddev *mddev, int journal_mode);
#endif