Assemble/force: make it possible to "force" a new device in a reshape.

Normally we do not "force"-assemble devices which are in the
middle of recovery, as they are unlikely to have useful data.

However, when a reshape increases the number of devices,
the newly added devices appear to be recovering because they
do not have complete data on them yet, but then they aren't expected
to until the reshape completes.
So in this case, it can be appropriate to force-assemble them.

Reported-by: "Jonathan Harker (Jesusaurus)" <jesusaurus@gentlydownthe.net>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 30 insertions, 5 deletions

diff --git a/Assemble.c b/Assemble.c
index 46ab72e..25a103d 100644
--- a/Assemble.c
+++ b/Assemble.c
@@ -817,12 +817,37 @@ static int force_array(struct mdinfo *content,
 		     i < content->array.raid_disks * 2 && i < bestcnt;
 		     i += 2) {
 			int j = best[i];
-			if (j>=0 &&
-			    !devices[j].uptodate &&
-			    devices[j].i.recovery_start == MaxSector &&
-			    (chosen_drive < 0 ||
+			if (j < 0)
+				continue;
+			if (devices[j].uptodate)
+				continue;
+			if (devices[j].i.recovery_start != MaxSector) {
+				int delta;
+				if (!devices[j].i.reshape_active ||
+				    devices[j].i.delta_disks <= 0)
+					continue;
+				/* When increasing number of devices, an
+				 * added device also appears to be
+				 * recovering.  It is safe to include it
+				 * as long as it won't be a source of
+				 * data.
+				 * For now, just allow for last data
+				 * devices in RAID4 or last devices in RAID4/5/6.
+				 */
+				delta = devices[j].i.delta_disks;
+				if (devices[j].i.array.level >= 4 &&
+				    devices[j].i.array.level <= 6 &&
+				    i/2 >= content->array.raid_disks - delta)
+					/* OK */;
+				else if (devices[j].i.array.level == 4 &&
+					 i/2 >= content->array.raid_disks - delta - 1)
+					/* OK */;
+				else
+					continue;
+			}
+			if (chosen_drive < 0 ||
 			     devices[j].i.events
-			     > devices[chosen_drive].i.events))
+			    > devices[chosen_drive].i.events)
 				chosen_drive = j;
 		}
 		if (chosen_drive < 0)