From 4b6c1060eaa6495aa5b0032e8f2d51dd936b1257 Mon Sep 17 00:00:00 2001
From: Heinz Mauelshagen <heinzm@redhat.com>
Date: Fri, 2 Feb 2018 23:13:19 +0100
Subject: md: fix md_write_start() deadlock w/o metadata devices

If no metadata devices are configured on raid1/4/5/6/10
(e.g. via dm-raid), md_write_start() unconditionally waits
for superblocks to be written thus deadlocking.

Fix introduces mddev->has_superblocks bool, defines it in md_run()
and checks for it in md_write_start() to conditionally avoid waiting.

Once on it, check for non-existing superblocks in md_super_write().

Link: https://bugzilla.kernel.org/show_bug.cgi?id=198647
Fixes: cc27b0c78c796 ("md: fix deadlock between mddev_suspend() and md_write_start()")

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Shaohua Li <sh.li@alibaba-inc.com>
---
 drivers/md/md.h | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'drivers/md/md.h')

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 58cd20a5e85e..fbc925cce810 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -468,6 +468,8 @@ struct mddev {
 	void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev);
 	struct md_cluster_info		*cluster_info;
 	unsigned int			good_device_nr;	/* good device num within cluster raid */
+
+	bool	has_superblocks:1;
 };
 
 enum recovery_flags {
-- 
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