md/raid5: use seqcount to protect access to shape in make_request.
make_request() access various shape parameters (raid_disks, chunk_size
etc) which might be changed by raid5_start_reshape().
If the later is called at and awkward time during the form, the wrong
stripe_head might be used.
So introduce a 'seqcount' and after finding a stripe_head make sure
there is no reason to expect that we got the wrong one.
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 1053663..435b12d 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -400,6 +400,7 @@
int prev_chunk_sectors;
int prev_algo;
short generation; /* increments with every reshape */
+ seqcount_t gen_lock; /* lock against generation changes */
unsigned long reshape_checkpoint; /* Time we last updated
* metadata */
long long min_offset_diff; /* minimum difference between