Hi, I have a suggest about mdadm to set disk faulty. Since commit 1ca69c4bc4b1ef
(md: avoid taking the mutex on some ioctls) removes lock when set disk faulty,
so we'd better using ioctl(SET_DISK_FAULTY) to set disk faulty, instead of 
echo faulty > /sys/block/<md>/md/dev-<disk>/state, because caller of state's
handler would lock mddev. Like following:

Index: mdadm-4.0/Manage.c
===================================================================

--- mdadm-4.0.orig/Manage.c
+++ mdadm-4.0/Manage.c

@@ -1662,9 +1662,7 @@ int Manage_subdevs(char *devname, int fd
 
 		case 'f': /* set faulty */
 			/* FIXME check current member */
-			if ((sysfd >= 0 && write(sysfd, "faulty", 6) != 6) ||
-			    (sysfd < 0 && ioctl(fd, SET_DISK_FAULTY,
-						rdev))) {
+			if (ioctl(fd, SET_DISK_FAULTY, rdev)) {
 				if (errno == EBUSY)
 					busy = 1;
 				pr_err("set device faulty failed for %s:  %s\n",