md: add 'write_error' flag to component devices.

If a device has ever seen a write error, we will want to handle
known-bad-blocks differently.
So create an appropriate state flag and export it via sysfs.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Namhyung Kim <namhyung@gmail.com>

drivers/md/md.c

@@ -2516,6 +2516,10 @@ state_show(mdk_rdev_t *rdev, char *page)
 		len += sprintf(page+len, "%sspare", sep);
 		sep = ",";
 	}
+	if (test_bit(WriteErrorSeen, &rdev->flags)) {
+		len += sprintf(page+len, "%swrite_error", sep);
+		sep = ",";
+	}
 	return len+sprintf(page+len, "\n");
 }
 
@@ -2530,6 +2534,8 @@ state_store(mdk_rdev_t *rdev, const char *buf, size_t len)
 	 *  blocked - sets the Blocked flag
 	 *  -blocked - clears the Blocked flag
 	 *  insync - sets Insync providing device isn't active
+	 *  write_error - sets WriteErrorSeen
+	 *  -write_error - clears WriteErrorSeen
 	 */
 	int err = -EINVAL;
 	if (cmd_match(buf, "faulty") && rdev->mddev->pers) {
@@ -2565,6 +2571,12 @@ state_store(mdk_rdev_t *rdev, const char *buf, size_t len)
 	} else if (cmd_match(buf, "insync") && rdev->raid_disk == -1) {
 		set_bit(In_sync, &rdev->flags);
 		err = 0;
+	} else if (cmd_match(buf, "write_error")) {
+		set_bit(WriteErrorSeen, &rdev->flags);
+		err = 0;
+	} else if (cmd_match(buf, "-write_error")) {
+		clear_bit(WriteErrorSeen, &rdev->flags);
+		err = 0;
 	}
 	if (!err)
 		sysfs_notify_dirent_safe(rdev->sysfs_state);

drivers/md/md.h

@@ -84,6 +84,9 @@ struct mdk_rdev_s
 #define Blocked		8		/* An error occurred on an externally
 					 * managed array, don't allow writes
 					 * until it is cleared */
+#define WriteErrorSeen	9		/* A write error has been seen on this
+					 * device
+					 */
 	wait_queue_head_t blocked_wait;
 
 	int desc_nr;			/* descriptor index in the superblock */