On (Wed) 07 Dec 2011 [12:37:02], Michael S. Tsirkin wrote:

On Wed, Dec 07, 2011 at 01:18:44AM +0530, Amit Shah wrote:

quoted

Delete the vq and flush any pending requests from the block queue on the
freeze callback to prepare for hibernation.

Re-create the vq in the restore callback to resume normal function.

Signed-off-by: Amit Shah <redacted>
---
 drivers/block/virtio_blk.c |   38 ++++++++++++++++++++++++++++++++++++++
 1 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 467f218..a9147a6 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c

@@ -568,6 +568,40 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
 	ida_simple_remove(&vd_index_ida, index);
 }
 
+#ifdef CONFIG_PM
+static int virtblk_freeze(struct virtio_device *vdev)
+{
+	struct virtio_blk *vblk = vdev->priv;
+
+	/* Ensure we don't receive any more interrupts */
+	vdev->config->reset(vdev);
+
+	flush_work(&vblk->config_work);

It bothers me that config work can be running
after reset here. If it does, it will not get sane
values from reading config.

Why so?

The reset only ensures the host doesn't write anything more, isn't it?
Why would the values be affected?

Also, can there be stuff in the reqs list?
If yes is this a problem?

Should be all cleared by the two commands below.  At least that's my
expectation.  If not, let me know!

quoted

+	spin_lock_irq(vblk->disk->queue->queue_lock);
+	blk_stop_queue(vblk->disk->queue);
+	spin_unlock_irq(vblk->disk->queue->queue_lock);
+	blk_sync_queue(vblk->disk->queue);
+
+	vdev->config->del_vqs(vdev);
+	return 0;
+}
+

Thinking about it, looks like there's a bug in
virtblk_remove: if we get a config change after
flush_work we schedule another work.
That's a problem for sure as structure is removed.

Yep, it is a potential issue.

		Amit