Once MD_BROKEN is set on an array, no further writes can be performed.
The user must be informed that the array cannot continue operation.

Add error logging when MD_BROKEN flag is set on raid1 arrays to improve
debugging and system administration visibility.

Signed-off-by: Kenta Akagi <k@mgml.me>
---
 drivers/md/raid1.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index bf96ae78a8b1..d58a60fb5b2f 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1790,6 +1790,10 @@ static void raid1_error(struct mddev *mddev, struct md_rdev *rdev)
 	if (test_bit(In_sync, &rdev->flags) &&
 	    (conf->raid_disks - mddev->degraded) == 1) {
 		set_bit(MD_BROKEN, &mddev->flags);
+		pr_crit("md/raid1:%s: Disk failure on %pg, this is the last device.\n"
+			"md/raid1:%s: Cannot continue operation (%d/%d failed).\n",
+			mdname(mddev), rdev->bdev,
+			mdname(mddev), mddev->degraded + 1, conf->raid_disks);
 
 		if (!mddev->fail_last_dev) {
 			conf->recovery_disabled = mddev->recovery_disabled;
-- 
2.50.1