[PATCH 2/2] virtio_blk: Add support for transport error recovery

[Israel Rukshin <israelr@nvidia.com>]

Add support for proper cleanup and re-initialization of virtio-blk devices
during transport reset error recovery flow.
This enhancement includes:
- Pre-reset handler (reset_prepare) to perform device-specific cleanup
- Post-reset handler (reset_done) to re-initialize the device

These changes allow the device to recover from various reset scenarios,
ensuring proper functionality after a reset event occurs.
Without this implementation, the device cannot properly recover from
resets, potentially leading to undefined behavior or device malfunction.

This feature has been tested using PCI transport with Function Level
Reset (FLR) as an example reset mechanism. The reset can be triggered
manually via sysfs (echo 1 > /sys/bus/pci/devices/$PCI_ADDR/reset).

Signed-off-by: Israel Rukshin <israelr@nvidia.com>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
---
 drivers/block/virtio_blk.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index c0cdba71f436..e1ab97251275 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -1582,8 +1582,7 @@ static void virtblk_remove(struct virtio_device *vdev)
 	put_disk(vblk->disk);
 }
 
-#ifdef CONFIG_PM_SLEEP
-static int virtblk_freeze(struct virtio_device *vdev)
+static int virtblk_freeze_priv(struct virtio_device *vdev)
 {
 	struct virtio_blk *vblk = vdev->priv;
 
@@ -1602,7 +1601,7 @@ static int virtblk_freeze(struct virtio_device *vdev)
 	return 0;
 }
 
-static int virtblk_restore(struct virtio_device *vdev)
+static int virtblk_restore_priv(struct virtio_device *vdev)
 {
 	struct virtio_blk *vblk = vdev->priv;
 	int ret;
@@ -1616,8 +1615,29 @@ static int virtblk_restore(struct virtio_device *vdev)
 	blk_mq_unfreeze_queue(vblk->disk->queue);
 	return 0;
 }
+
+#ifdef CONFIG_PM_SLEEP
+static int virtblk_freeze(struct virtio_device *vdev)
+{
+	return virtblk_freeze_priv(vdev);
+}
+
+static int virtblk_restore(struct virtio_device *vdev)
+{
+	return virtblk_restore_priv(vdev);
+}
 #endif
 
+static int virtblk_reset_prepare(struct virtio_device *vdev)
+{
+	return virtblk_freeze_priv(vdev);
+}
+
+static int virtblk_reset_done(struct virtio_device *vdev)
+{
+	return virtblk_restore_priv(vdev);
+}
+
 static const struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_BLOCK, VIRTIO_DEV_ANY_ID },
 	{ 0 },
@@ -1653,6 +1673,8 @@ static struct virtio_driver virtio_blk = {
 	.freeze				= virtblk_freeze,
 	.restore			= virtblk_restore,
 #endif
+	.reset_prepare			= virtblk_reset_prepare,
+	.reset_done			= virtblk_reset_done,
 };
 
 static int __init virtio_blk_init(void)
-- 
2.34.1