linux-kernel - [PATCH 2/2] Drivers: hv: vmbus: Fix rescind handling in uio_hv

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Message-Id: <20240822110912.13735-3-namjain@linux.microsoft.com>
Date: Thu, 22 Aug 2024 16:39:12 +0530
From: Naman Jain <namjain@...ux.microsoft.com>
To: "K . Y . Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Stephen Hemminger <stephen@...workplumber.org>
Cc: linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Saurabh Sengar <ssengar@...ux.microsoft.com>,
	Naman Jain <namjain@...ux.microsoft.com>
Subject: [PATCH 2/2] Drivers: hv: vmbus: Fix rescind handling in uio_hv_generic

Rescind offer handling relies on rescind callbacks for some of the
resources cleanup, if they are registered. It does not unregister
vmbus device for the primary channel closure, when callback is
registered.
Add logic to unregister vmbus for the primary channel in rescind callback
to ensure channel removal and relid release, and to ensure rescind flag
is false when driver probe happens again.

Fixes: ca3cda6fcf1e ("uio_hv_generic: add rescind support")
Signed-off-by: Naman Jain <namjain@...ux.microsoft.com>
---
 drivers/hv/vmbus_drv.c       | 1 +
 drivers/uio/uio_hv_generic.c | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index c857dc3975be..4bae382a3eb4 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1952,6 +1952,7 @@ void vmbus_device_unregister(struct hv_device *device_obj)
 	 */
 	device_unregister(&device_obj->device);
 }
+EXPORT_SYMBOL_GPL(vmbus_device_unregister);
 
 #ifdef CONFIG_ACPI
 /*
diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index c99890c16d29..ea26c0b460d6 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -121,6 +121,13 @@ static void hv_uio_rescind(struct vmbus_channel *channel)
 
 	/* Wake up reader */
 	uio_event_notify(&pdata->info);
+
+	/*
+	 * With rescind callback registered, rescind path will not unregister the device
+	 * when the primary channel is rescinded. Without it, next onoffer msg does not come.
+	 */
+	if (!channel->primary_channel)
+		vmbus_device_unregister(channel->device_obj);
 }
 
 /* Sysfs API to allow mmap of the ring buffers
-- 
2.34.1