[md PATCH 04/18] md/raid10: add rcu protection in raid10_status.

NeilBrown
2016-06-02T06:19:52Z

mirrors[].rdev can become NULL at any point unless:
- a counted reference is held
- ->reconfig_mutex is held, or
- rcu_read_lock() is held

raid10_status holds none of these. So add rcu_read_lock()
protection.

Signed-off-by: NeilBrown <neilb@suse.com>
---
drivers/md/raid10.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index f371d45f786a..e6f3a11f8f70 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1495,10 +1495,12 @@ static void raid10_status(struct seq_file *seq, struct mddev *mddev)
}
seq_printf(seq, " [%d/%d] [", conf->geo.raid_disks,
conf->geo.raid_disks - mddev->degraded);
- for (i = 0; i < conf->geo.raid_disks; i++)
- seq_printf(seq, "%s",
- conf->mirrors[i].rdev &&
- test_bit(In_sync, &conf->mirrors[i].rdev->flags) ? "U" : "_");
+ rcu_read_lock();
+ for (i = 0; i < conf->geo.raid_disks; i++) {
+ struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+ seq_printf(seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
+ }
+ rcu_read_unlock();
seq_printf(seq, "]");
}