DM RAID: Fix for "sync" directive ineffectiveness

There are two table arguments that can be given to a DM RAID target
that control whether the array is forced to (re)synchronize or skip
initialization: "sync" and "nosync".  When "sync" is given, we set
mddev->recovery_cp to 0 in order to cause the device to resynchronize.
This is insufficient if there is a bitmap in use, because the array
will simply look at the bitmap and see that there is no recovery
necessary.

The fix is to skip over the loading of the superblocks when "sync" is
given, causing new superblocks to be written that will force the array
to go through initialization (i.e. synchronization).

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 89a06a36133218a2c650036dbf3751c7ccd8aec4..45d94a7e7f6db798ce291546f7916b246203f85b 100644 (file)
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -1017,6 +1017,19 @@ static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
 
        freshest = NULL;
        rdev_for_each_safe(rdev, tmp, mddev) {
+               /*
+                * Skipping super_load due to DMPF_SYNC will cause
+                * the array to undergo initialization again as
+                * though it were new.  This is the intended effect
+                * of the "sync" directive.
+                *
+                * When reshaping capability is added, we must ensure
+                * that the "sync" directive is disallowed during the
+                * reshape.
+                */
+               if (rs->print_flags & DMPF_SYNC)
+                       continue;
+
                if (!rdev->meta_bdev)
                        continue;