dm cache: make sure every metadata function checks fail_io

Otherwise operations may be attempted that will only ever go on to crash
(since the metadata device is either missing or unreliable if 'fail_io'
is set).

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 2238d6f..43d9e9a 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -984,9 +984,14 @@
 
 static void set_cache_mode(struct cache *cache, enum cache_metadata_mode new_mode)
 {
-	bool needs_check = dm_cache_metadata_needs_check(cache->cmd);
+	bool needs_check;
 	enum cache_metadata_mode old_mode = get_cache_mode(cache);
 
+	if (dm_cache_metadata_needs_check(cache->cmd, &needs_check)) {
+		DMERR("unable to read needs_check flag, setting failure mode");
+		new_mode = CM_FAIL;
+	}
+
 	if (new_mode == CM_WRITE && needs_check) {
 		DMERR("%s: unable to switch cache to write mode until repaired.",
 		      cache_device_name(cache));
@@ -3510,6 +3515,7 @@
 	char buf[BDEVNAME_SIZE];
 	struct cache *cache = ti->private;
 	dm_cblock_t residency;
+	bool needs_check;
 
 	switch (type) {
 	case STATUSTYPE_INFO:
@@ -3583,7 +3589,9 @@
 		else
 			DMEMIT("rw ");
 
-		if (dm_cache_metadata_needs_check(cache->cmd))
+		r = dm_cache_metadata_needs_check(cache->cmd, &needs_check);
+
+		if (r || needs_check)
 			DMEMIT("needs_check ");
 		else
 			DMEMIT("- ");