2 files changed, 38 insertions, 13 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 5265975b3fba..e1c6798889f4 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -945,7 +945,8 @@ static void blkif_set_queue_limits(struct blkfront_info *info)
 	if (info->feature_discard) {
 		blk_queue_flag_set(QUEUE_FLAG_DISCARD, rq);
 		blk_queue_max_discard_sectors(rq, get_capacity(gd));
-		rq->limits.discard_granularity = info->discard_granularity;
+		rq->limits.discard_granularity = info->discard_granularity ?:
+						 info->physical_sector_size;
 		rq->limits.discard_alignment = info->discard_alignment;
 		if (info->feature_secdiscard)
 			blk_queue_flag_set(QUEUE_FLAG_SECERASE, rq);
@@ -2179,19 +2180,12 @@ static void blkfront_closing(struct blkfront_info *info)
 
 static void blkfront_setup_discard(struct blkfront_info *info)
 {
-	int err;
-	unsigned int discard_granularity;
-	unsigned int discard_alignment;
-
 	info->feature_discard = 1;
-	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
-		"discard-granularity", "%u", &discard_granularity,
-		"discard-alignment", "%u", &discard_alignment,
-		NULL);
-	if (!err) {
-		info->discard_granularity = discard_granularity;
-		info->discard_alignment = discard_alignment;
-	}
+	info->discard_granularity = xenbus_read_unsigned(info->xbdev->otherend,
+							 "discard-granularity",
+							 0);
+	info->discard_alignment = xenbus_read_unsigned(info->xbdev->otherend,
+						       "discard-alignment", 0);
 	info->feature_secdiscard =
 		!!xenbus_read_unsigned(info->xbdev->otherend, "discard-secure",
 				       0);
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index c8f0282bb649..18ffd0551b54 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -714,6 +714,23 @@ static bool xs_hvm_defer_init_for_callback(void)
 #endif
 }
 
+static int xenbus_probe_thread(void *unused)
+{
+	DEFINE_WAIT(w);
+
+	/*
+	 * We actually just want to wait for *any* trigger of xb_waitq,
+	 * and run xenbus_probe() the moment it occurs.
+	 */
+	prepare_to_wait(&xb_waitq, &w, TASK_INTERRUPTIBLE);
+	schedule();
+	finish_wait(&xb_waitq, &w);
+
+	DPRINTK("probing");
+	xenbus_probe();
+	return 0;
+}
+
 static int __init xenbus_probe_initcall(void)
 {
 	/*
@@ -725,6 +742,20 @@ static int __init xenbus_probe_initcall(void)
 	     !xs_hvm_defer_init_for_callback()))
 		xenbus_probe();
 
+	/*
+	 * For XS_LOCAL, spawn a thread which will wait for xenstored
+	 * or a xenstore-stubdom to be started, then probe. It will be
+	 * triggered when communication starts happening, by waiting
+	 * on xb_waitq.
+	 */
+	if (xen_store_domain_type == XS_LOCAL) {
+		struct task_struct *probe_task;
+
+		probe_task = kthread_run(xenbus_probe_thread, NULL,
+					 "xenbus_probe");
+		if (IS_ERR(probe_task))
+			return PTR_ERR(probe_task);
+	}
 	return 0;
 }
 device_initcall(xenbus_probe_initcall);