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Date:      Tue, 22 May 2018 08:51:17 +0000 (UTC)
From:      =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <royger@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r334027 - head/sys/dev/xen/blkback
Message-ID:  <201805220851.w4M8pHne063550@repo.freebsd.org>
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Author: royger
Date: Tue May 22 08:51:16 2018
New Revision: 334027
URL: https://svnweb.freebsd.org/changeset/base/334027

Log:
  xen-blkback: do not use state 3 (XenbusStateInitialised)
  
  Linux will not connect to a backend that's in state 3
  (XenbusStateInitialised), it needs to be in state 2
  (XenbusStateInitWait) for Linux to attempt to connect to the backend.
  
  The protocol seems to suggest that the backend should indeed wait in
  state 2 for the frontend to connect, which makes state 3 unusable for
  disk backends.
  
  Also make sure blkback will connect to the frontend if the frontend
  reaches state 3 (XenbusStateInitialised) before blkback has processed
  the results from the hotplug script (Submitted by Nathan Friess).
  
  MFC after:	1 week

Modified:
  head/sys/dev/xen/blkback/blkback.c

Modified: head/sys/dev/xen/blkback/blkback.c
==============================================================================
--- head/sys/dev/xen/blkback/blkback.c	Tue May 22 08:27:33 2018	(r334026)
+++ head/sys/dev/xen/blkback/blkback.c	Tue May 22 08:51:16 2018	(r334027)
@@ -806,6 +806,9 @@ struct xbb_softc {
 
 	/** Watch to wait for hotplug script execution */
 	struct xs_watch		  hotplug_watch;
+
+	/** Got the needed data from hotplug scripts? */
+	bool			  hotplug_done;
 };
 
 /*---------------------------- Request Processing ----------------------------*/
@@ -3310,12 +3313,11 @@ xbb_connect(struct xbb_softc *xbb)
 {
 	int error;
 
-	if (xenbus_get_state(xbb->dev) != XenbusStateInitialised)
+	if (!xbb->hotplug_done ||
+	    (xenbus_get_state(xbb->dev) != XenbusStateInitWait) ||
+	    (xbb_collect_frontend_info(xbb) != 0))
 		return;
 
-	if (xbb_collect_frontend_info(xbb) != 0)
-		return;
-
 	xbb->flags &= ~XBBF_SHUTDOWN;
 
 	/*
@@ -3412,6 +3414,7 @@ xbb_shutdown(struct xbb_softc *xbb)
 		free(xbb->hotplug_watch.node, M_XENBLOCKBACK);
 		xbb->hotplug_watch.node = NULL;
 	}
+	xbb->hotplug_done = false;
 
 	if (xenbus_get_state(xbb->dev) < XenbusStateClosing)
 		xenbus_set_state(xbb->dev, XenbusStateClosing);
@@ -3692,8 +3695,11 @@ xbb_attach_disk(struct xs_watch *watch, const char **v
 		return;
 	}
 
-	/* Tell the front end that we are ready to connect. */
-	xenbus_set_state(dev, XenbusStateInitialised);
+	xbb->hotplug_done = true;
+
+	/* The front end might be waiting for the backend, attach if so. */
+	if (xenbus_get_otherend_state(xbb->dev) == XenbusStateInitialised)
+		xbb_connect(xbb);
 }
 
 /**
@@ -3757,6 +3763,7 @@ xbb_attach(device_t dev)
 	 * We need to wait for hotplug script execution before
 	 * moving forward.
 	 */
+	KASSERT(!xbb->hotplug_done, ("Hotplug scripts already executed"));
 	watch_path = xs_join(xenbus_get_node(xbb->dev), "physical-device-path");
 	xbb->hotplug_watch.callback_data = (uintptr_t)dev;
 	xbb->hotplug_watch.callback = xbb_attach_disk;

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