md: make sure metadata is updated when spares are activated or removed.

It isn't always necessary to update the metadata when spares are
removed as the presence-or-not of a spare isn't really important to
the integrity of an array.
Also activating a spare doesn't always require updating the metadata
as the update on 'recovery-completed' is usually sufficient.

However the introduction of 'replacement' devices have made these
transitions sometimes more important.  For example the 'Replacement'
flag isn't cleared until the original device is removed, so we need
to ensure a metadata update after that 'spare' is removed.

So set MD_CHANGE_DEVS whenever a spare is activated or removed, to
complement the current situation where it is set when a spare is added
or a device is failed (or a number of other less common situations).

This is suitable for -stable as out-of-data metadata could lead
to data corruption.
This is only relevant for 3.3 and later 9when 'replacement' as
introduced.

Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3f6203a4c7ea0dd730b80a6b441b99e8a4da3216..308e87b417e05a74e4429bac63e1eb2e7af43885 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7619,6 +7619,8 @@ static int remove_and_add_spares(struct mddev *mddev)
                        }
                }
        }
+       if (removed)
+               set_bit(MD_CHANGE_DEVS, &mddev->flags);
        return spares;
 }
 
@@ -7632,9 +7634,11 @@ static void reap_sync_thread(struct mddev *mddev)
            !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
                /* success...*/
                /* activate any spares */
-               if (mddev->pers->spare_active(mddev))
+               if (mddev->pers->spare_active(mddev)) {
                        sysfs_notify(&mddev->kobj, NULL,
                                     "degraded");
+                       set_bit(MD_CHANGE_DEVS, &mddev->flags);
+               }
        }
        if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
            mddev->pers->finish_reshape)