Ensure interrupted recovery completed properly (v1 metadata plus bitmap)

If, while assembling an array, we find a device which is not fully
in-sync with the array, it is important to set the "fullsync" flags.
This is an exact analog to the setting of this flag in hot_add_disk
methods.

Currently, only v1.x metadata supports having devices in an array
which are not fully in-sync (it keep track of how in sync they are).
The 'fullsync' flag only makes a difference when a write-intent bitmap
is being used.  In this case it tells recovery to ignore the bitmap
and recovery all blocks.

This fix is already in place for raid1, but not raid5/6 or raid10.

So without this fix, a raid1 ir raid4/5/6 array with version 1.x
metadata and a write intent bitmaps, that is stopped in the middle
of a recovery, will appear to complete the recovery instantly
after it is reassembled, but the recovery will not be correct.

If you might have an array like that, issueing
   echo repair > /sys/block/mdXX/md/sync_action

will make sure recovery completes properly.

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

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index c37e256b1176..475fba4d371e 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4305,7 +4305,9 @@ static int run(mddev_t *mddev)
                                 " disk %d\n", bdevname(rdev->bdev,b),
                                 raid_disk);
                         working_disks++;
-                }
+                } else
+                        /* Cannot rely on bitmap to complete recovery */
+                        conf->fullsync = 1;
         }
 
         /*