dm raid: fix incorrect sync_ratio when degraded

Upstream commit 4102d9de ("dm raid: fix rs_get_progress()
synchronization state/ratio") in combination with commit 7c29744e
("dm raid: simplify rs_get_progress()") introduced a regression by
incorrectly reporting a sync_ratio of 0 for degraded raid sets.  This
caused lvm2 to fail to repair raid legs automatically.

Fix by identifying the degraded state by checking the MD_RECOVERY_INTR
flag and returning mddev->recovery_cp in case it is set.

MD sets recovery = [ MD_RECOVERY_RECOVER MD_RECOVERY_INTR
MD_RECOVERY_NEEDED ] when a RAID member fails.  It then shuts down any
sync thread that is running and leaves us with all MD_RECOVERY_* flags
cleared.  The bug occurs if a status is requested in the short time it
takes to shut down any sync thread and clear the flags, because we were
keying in on the MD_RECOVERY_NEEDED - understanding it to be the initial
phase of a “recover” sync thread.  However, this is an incorrect
interpretation if MD_RECOVERY_INTR is also set.

This also explains why the bug only happened when automatic repair was
enabled and not a normal ‘manual’ method.  It is impossible to react
quick enough to hit the problematic window without it being automated.

Fix passes automatic repair tests.

Fixes: 7c29744e ("dm raid: simplify rs_get_progress()")
Signed-off-by: NJonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NHeinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

drivers/md/dm-raid.c

@@ -3408,9 +3408,10 @@ static sector_t rs_get_progress(struct raid_set *rs, unsigned long recovery,
 		set_bit(RT_FLAG_RS_IN_SYNC, &rs->runtime_flags);
 
 	} else {
-		if (test_bit(MD_RECOVERY_NEEDED, &recovery) ||
-		    test_bit(MD_RECOVERY_RESHAPE, &recovery) ||
-		    test_bit(MD_RECOVERY_RUNNING, &recovery))
+		if (!test_bit(MD_RECOVERY_INTR, &recovery) &&
+		    (test_bit(MD_RECOVERY_NEEDED, &recovery) ||
+		     test_bit(MD_RECOVERY_RESHAPE, &recovery) ||
+		     test_bit(MD_RECOVERY_RUNNING, &recovery)))
 			r = mddev->curr_resync_completed;
 		else
 			r = mddev->recovery_cp;