md/raid1: Mark device want_replacement when we see a write error.

Now that WantReplacement drives are replaced cleanly, mark a drive
as want_replacement when we see a write error.  It might get failed soon so
the WantReplacement flag is irrelevant, but if the write error is recorded
in the bad block log, we still want to activate any spare that might
be available.

Signed-off-by:  NeilBrown <neilb@suse.de>

drivers/md/raid1.c

@@ -391,6 +391,11 @@ static void raid1_end_write_request(struct bio *bio, int error)
 	if (!uptodate) {
 		set_bit(WriteErrorSeen,
 			&conf->mirrors[mirror].rdev->flags);
+		if (!test_and_set_bit(WantReplacement,
+				      &conf->mirrors[mirror].rdev->flags))
+			set_bit(MD_RECOVERY_NEEDED, &
+				conf->mddev->recovery);
+
 		set_bit(R1BIO_WriteError, &r1_bio->state);
 	} else {
 		/*
@@ -1461,6 +1466,10 @@ static void end_sync_write(struct bio *bio, int error)
 		} while (sectors_to_go > 0);
 		set_bit(WriteErrorSeen,
 			&conf->mirrors[mirror].rdev->flags);
+		if (!test_and_set_bit(WantReplacement,
+				      &conf->mirrors[mirror].rdev->flags))
+			set_bit(MD_RECOVERY_NEEDED, &
+				mddev->recovery);
 		set_bit(R1BIO_WriteError, &r1_bio->state);
 	} else if (is_badblock(conf->mirrors[mirror].rdev,
 			       r1_bio->sector,
@@ -1491,8 +1500,13 @@ static int r1_sync_page_io(struct md_rdev *rdev, sector_t sector,
 	if (sync_page_io(rdev, sector, sectors << 9, page, rw, false))
 		/* success */
 		return 1;
-	if (rw == WRITE)
+	if (rw == WRITE) {
 		set_bit(WriteErrorSeen, &rdev->flags);
+		if (!test_and_set_bit(WantReplacement,
+				      &rdev->flags))
+			set_bit(MD_RECOVERY_NEEDED, &
+				rdev->mddev->recovery);
+	}
 	/* need to record an error - either for the block or the device */
 	if (!rdev_set_badblocks(rdev, sector, sectors, 0))
 		md_error(rdev->mddev, rdev);