md/raid5: handle possible race as reshape completes.
It is possible (though unlikely) for a reshape to be
interrupted between the time that end_reshape is called
and the time when raid5_finish_reshape is called.
This can leave conf->reshape_progress set to MaxSector,
but mddev->reshape_position not.
This combination confused reshape_request() when ->reshape_backwards.
As conf->reshape_progress is so high, it seems the reshape hasn't
really begun. But assuming MaxSector is a valid address only
leads to sorrow.
So ensure reshape_position and reshape_progress both agree,
and add an extra check in reshape_request() just in case they don't.
Signed-off-by: NeilBrown <neilb@suse.com>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 1c27aa1..7b0c706 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5355,6 +5355,10 @@
conf->reshape_progress < raid5_size(mddev, 0, 0)) {
sector_nr = raid5_size(mddev, 0, 0)
- conf->reshape_progress;
+ } else if (mddev->reshape_backwards &&
+ conf->reshape_progress == MaxSector) {
+ /* shouldn't happen, but just in case, finish up.*/
+ sector_nr = MaxSector;
} else if (!mddev->reshape_backwards &&
conf->reshape_progress > 0)
sector_nr = conf->reshape_progress;
@@ -7446,6 +7450,7 @@
rdev->data_offset = rdev->new_data_offset;
smp_wmb();
conf->reshape_progress = MaxSector;
+ conf->mddev->reshape_position = MaxSector;
spin_unlock_irq(&conf->device_lock);
wake_up(&conf->wait_for_overlap);