linux-kernel - [PATCH V2] virtio-blk: Ensure no requests in virtqueues before deleting vqs.

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Date: Mon, 29 Jan 2024 16:52:50 +0800
From: Yi Sun <yi.sun@...soc.com>
To: <stefanha@...hat.com>, <mst@...hat.com>, <jasowang@...hat.com>,
        <axboe@...nel.dk>
CC: <yi.sun@...soc.com>, <sunyibuaa@...il.com>, <hongyu.jin@...soc.com>,
        <zhiguo.niu@...soc.com>, <xuanzhuo@...ux.alibaba.com>,
        <pbonzini@...hat.com>, <virtualization@...ts.linux.dev>,
        <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH V2] virtio-blk: Ensure no requests in virtqueues before deleting vqs.

Ensure no remaining requests in virtqueues before resetting vdev and
deleting virtqueues. Otherwise these requests will never be completed.
It may cause the system to become unresponsive.

Function blk_mq_quiesce_queue() can ensure that requests have become
in_flight status, but it cannot guarantee that requests have been
processed by the device. Virtqueues should never be deleted before
all requests become complete status.

Function blk_mq_freeze_queue() ensure that all requests in virtqueues
become complete status. And no requests can enter in virtqueues.

Signed-off-by: Yi Sun <yi.sun@...soc.com>
---
 drivers/block/virtio_blk.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 3b6b9abb8ce1..14ecc14ce8db 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -1595,14 +1595,15 @@ static int virtblk_freeze(struct virtio_device *vdev)
 {
 	struct virtio_blk *vblk = vdev->priv;

+	/* Ensure no requests in virtqueues before deleting vqs. */
+	blk_mq_freeze_queue(vblk->disk->queue);
+
 	/* Ensure we don't receive any more interrupts */
 	virtio_reset_device(vdev);

 	/* Make sure no work handler is accessing the device. */
 	flush_work(&vblk->config_work);

-	blk_mq_quiesce_queue(vblk->disk->queue);
-
 	vdev->config->del_vqs(vdev);
 	kfree(vblk->vqs);

@@ -1620,7 +1621,7 @@ static int virtblk_restore(struct virtio_device *vdev)

 	virtio_device_ready(vdev);

-	blk_mq_unquiesce_queue(vblk->disk->queue);
+	blk_mq_unfreeze_queue(vblk->disk->queue);
 	return 0;
 }
 #endif
-- 
2.25.1