md: introduce new personality funciton start()

In do_md_run(), md threads should not wake up until the array is fully
initialized in md_run(). However, in raid5_run(), raid5-cache may wake
up mddev->thread to flush stripes that need to be written back. This
design doesn't break badly right now. But it could lead to bad bug in
the future.

This patch tries to resolve this problem by splitting start up work
into two personality functions, run() and start(). Tasks that do not
require the md threads should go into run(), while task that require
the md threads go into start().

r5l_load_log() is moved to raid5_start(), so it is not called until
the md threads are started in do_md_run().

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 6319d846e0ad..e5ef0757fe23 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3151,6 +3151,14 @@ static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto bad;
 	}
 
+	r = md_start(&rs->md);
+
+	if (r) {
+		ti->error = "Failed to start raid array";
+		mddev_unlock(&rs->md);
+		goto bad_md_start;
+	}
+
 	rs->callbacks.congested_fn = raid_is_congested;
 	dm_table_add_target_callbacks(ti->table, &rs->callbacks);
 
@@ -3198,6 +3206,7 @@ static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	mddev_unlock(&rs->md);
 	return 0;
 
+bad_md_start:
 bad_journal_mode_set:
 bad_stripe_cache:
 bad_check_reshape: