[PATCH] mdadm: fix reshape from RAID5 to RAID6 with backup file

[Nigel Croxon <ncroxon@redhat.com>]

Reshaping a 3-disk RAID5 to 4-disk RAID6 will cause a hang of
the resync after the grow.

Adding a spare disk to avoid degrading the array when growing
is successful, but not successful when supplying a backup file
on the command line. If the reshape job is not already running,
set the sync_max value to max.

Signed-off-by: Nigel Croxon <ncroxon@redhat.com>
---
 Grow.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Grow.c b/Grow.c
index 6b8321c..5c2512f 100644
--- a/Grow.c
+++ b/Grow.c
@@ -931,12 +931,15 @@ int start_reshape(struct mdinfo *sra, int already_running,
 	err = err ?: sysfs_set_num(sra, NULL, "sync_max", sync_max_to_set);
 	if (!already_running && err == 0) {
 		int cnt = 5;
+		int err2;
 		do {
 			err = sysfs_set_str(sra, NULL, "sync_action",
 					    "reshape");
-			if (err)
+			err2 = sysfs_set_str(sra, NULL, "sync_max",
+					    "max");
+			if (err || err2)
 				sleep(1);
-		} while (err && errno == EBUSY && cnt-- > 0);
+		} while (err && err2 && errno == EBUSY && cnt-- > 0);
 	}
 	return err;
 }
-- 
2.20.1