md: Don't acknowlege that stripe-expand is complete until it really is.

commit efe311431869b40d67911820a309f9a1a41306f3 upstream

We shouldn't acknowledge that a stripe has been expanded (When
reshaping a raid5 by adding a device) until the moved data has
actually been written out.  However we are currently
acknowledging (by calling md_done_sync) when the POST_XOR
is complete and before the write.

So track in s.locked whether there are pending writes, and don't
call md_done_sync yet if there are.

Note: we all set R5_LOCKED on devices which are are about to
read from.  This probably isn't technically necessary, but is
usually done when writing a block, and justifies the use of
s.locked here.

This bug can lead to a crash if an array is stopped while an reshape
is in progress.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 705fe473c694f467cdfb605e95f4c3367c691d79..61cbdc6e2012218a7b6444eb7251107dbe323033 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2861,6 +2861,8 @@ static void handle_stripe5(struct stripe_head *sh)
 
                for (i = conf->raid_disks; i--; ) {
                        set_bit(R5_Wantwrite, &sh->dev[i].flags);
+                       set_bit(R5_LOCKED, &dev->flags);
+                       s.locked++;
                        if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
                                sh->ops.count++;
                }
@@ -2874,6 +2876,7 @@ static void handle_stripe5(struct stripe_head *sh)
                        conf->raid_disks);
                s.locked += handle_write_operations5(sh, 1, 1);
        } else if (s.expanded &&
+                  s.locked == 0 &&
                !test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
                clear_bit(STRIPE_EXPAND_READY, &sh->state);
                atomic_dec(&conf->reshape_stripes);