---

yaml
---
r: 346220
b: refs/heads/master
c: 6f3465e
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 0c849666016cbf541c1030eec55f5f8dd1fba513
+refs/heads/master: 6f3465ed82b10922effe364676103cbd4f2bcd81

trunk/drivers/block/drbd/drbd_int.h

@@ -815,6 +815,12 @@ enum {
 	CONN_DRY_RUN,		/* Expect disconnect after resync handshake. */
 	CREATE_BARRIER,		/* next P_DATA is preceded by a P_BARRIER */
 	STATE_SENT,		/* Do not change state/UUIDs while this is set */
+	CALLBACK_PENDING,	/* Whether we have a call_usermodehelper(, UMH_WAIT_PROC)
+				 * pending, from drbd worker context.
+				 * If set, bdi_write_congested() returns true,
+				 * so shrink_page_list() would not recurse into,
+				 * and potentially deadlock on, this drbd worker.
+				 */
 };
 
 struct drbd_tconn {			/* is a resource from the config file */

trunk/drivers/block/drbd/drbd_main.c

@@ -2338,6 +2338,22 @@ static int drbd_congested(void *congested_data, int bdi_bits)
 		goto out;
 	}
 
+	if (test_bit(CALLBACK_PENDING, &mdev->tconn->flags)) {
+		r |= (1 << BDI_async_congested);
+		/* Without good local data, we would need to read from remote,
+		 * and that would need the worker thread as well, which is
+		 * currently blocked waiting for that usermode helper to
+		 * finish.
+		 */
+		if (!get_ldev_if_state(mdev, D_UP_TO_DATE))
+			r |= (1 << BDI_sync_congested);
+		else
+			put_ldev(mdev);
+		r &= bdi_bits;
+		reason = 'c';
+		goto out;
+	}
+
 	if (get_ldev(mdev)) {
 		q = bdev_get_queue(mdev->ldev->backing_bdev);
 		r = bdi_congested(&q->backing_dev_info, bdi_bits);

trunk/drivers/block/drbd/drbd_nl.c

@@ -323,11 +323,15 @@ int drbd_khelper(struct drbd_conf *mdev, char *cmd)
 			NULL };
 	char mb[12];
 	char *argv[] = {usermode_helper, cmd, mb, NULL };
+	struct drbd_tconn *tconn = mdev->tconn;
 	struct sib_info sib;
 	int ret;
 
+	if (current == tconn->worker.task)
+		set_bit(CALLBACK_PENDING, &tconn->flags);
+
 	snprintf(mb, 12, "minor-%d", mdev_to_minor(mdev));
-	setup_khelper_env(mdev->tconn, envp);
+	setup_khelper_env(tconn, envp);
 
 	/* The helper may take some time.
 	 * write out any unsynced meta data changes now */
@@ -350,6 +354,9 @@ int drbd_khelper(struct drbd_conf *mdev, char *cmd)
 	sib.helper_exit_code = ret;
 	drbd_bcast_event(mdev, &sib);
 
+	if (current == tconn->worker.task)
+		clear_bit(CALLBACK_PENDING, &tconn->flags);
+
 	if (ret < 0) /* Ignore any ERRNOs we got. */
 		ret = 0;