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Date: Thu, 27 Jan 2011 17:32:21 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Christoph Hellwig <hch@....de>
Cc: Rusty Russell <rusty@...tcorp.com.au>,
linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
kvm@...r.kernel.org
Subject: Re: [PATCH] virtio_blk: allow re-reading config space at runtime
On Fri, Jan 14, 2011 at 05:01:37PM +0100, Christoph Hellwig wrote:
> Wire up the virtio_driver config_changed method to get notified about
> config changes raised by the host. For now we just re-read the device
> size to support online resizing of devices, but once we add more
> attributes that might be changeable they could be added as well.
>
> Note that the config_changed method is called from irq context, so
> we'll have to use the workqueue infrastructure to provide us a proper
> user context for our changes.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
>
> Index: xfs/drivers/block/virtio_blk.c
> ===================================================================
> --- xfs.orig/drivers/block/virtio_blk.c 2011-01-13 18:17:23.730254665 +0100
> +++ xfs/drivers/block/virtio_blk.c 2011-01-14 16:57:50.572032906 +0100
> @@ -6,10 +6,12 @@
> #include <linux/virtio.h>
> #include <linux/virtio_blk.h>
> #include <linux/scatterlist.h>
> +#include <linux/string_helpers.h>
>
> #define PART_BITS 4
>
> static int major, index;
> +struct workqueue_struct *virtblk_wq;
>
> struct virtio_blk
> {
> @@ -42,6 +44,11 @@ struct virtblk_req
> u8 status;
> };
>
> +struct virtblk_config_change {
> + struct virtio_device *vdev;
> + struct work_struct work;
> +};
> +
> static void blk_done(struct virtqueue *vq)
> {
> struct virtio_blk *vblk = vq->vdev->priv;
> @@ -291,6 +298,57 @@ static ssize_t virtblk_serial_show(struc
> }
> DEVICE_ATTR(serial, S_IRUGO, virtblk_serial_show, NULL);
>
> +static void virtblk_config_changed_work(struct work_struct *work)
> +{
> + struct virtblk_config_change *cfg =
> + container_of(work, struct virtblk_config_change, work);
> + struct virtio_device *vdev = cfg->vdev;
> + struct virtio_blk *vblk = vdev->priv;
> + struct request_queue *q = vblk->disk->queue;
> + char cap_str_2[10], cap_str_10[10];
> + u64 capacity, size;
> +
> + /* Host must always specify the capacity. */
> + vdev->config->get(vdev, offsetof(struct virtio_blk_config, capacity),
> + &capacity, sizeof(capacity));
> +
> + /* If capacity is too big, truncate with warning. */
> + if ((sector_t)capacity != capacity) {
> + dev_warn(&vdev->dev, "Capacity %llu too large: truncating\n",
> + (unsigned long long)capacity);
> + capacity = (sector_t)-1;
> + }
> +
> + size = capacity * queue_logical_block_size(q);
> + string_get_size(size, STRING_UNITS_2, cap_str_2, sizeof(cap_str_2));
> + string_get_size(size, STRING_UNITS_10, cap_str_10, sizeof(cap_str_10));
> +
> + dev_notice(&vdev->dev,
> + "new size: %llu %d-byte logical blocks (%s/%s)\n",
> + (unsigned long long)capacity,
> + queue_logical_block_size(q),
> + cap_str_10, cap_str_2);
> +
> + set_capacity(vblk->disk, capacity);
> +
> +}
> +
> +static void virtblk_config_changed(struct virtio_device *vdev)
> +{
> + struct virtblk_config_change *cfg;
> +
> + cfg = kmalloc(sizeof(*cfg), GFP_ATOMIC);
> + if (!cfg) {
> + dev_info(&vdev->dev, "skipping config change\n");
> + return;
> + }
> +
> + cfg->vdev = vdev;
> + INIT_WORK(&cfg->work, virtblk_config_changed_work);
> + queue_work(virtblk_wq, &cfg->work);
This needs to be flushed on device removal, I think,
otherwise the vdev pointer will go stale.
> +}
> +
> +
Two empty lines :)
> static int __devinit virtblk_probe(struct virtio_device *vdev)
> {
> struct virtio_blk *vblk;
> @@ -508,27 +566,47 @@ static unsigned int features[] = {
> * Use __refdata to avoid this warning.
> */
> static struct virtio_driver __refdata virtio_blk = {
> - .feature_table = features,
> - .feature_table_size = ARRAY_SIZE(features),
> - .driver.name = KBUILD_MODNAME,
> - .driver.owner = THIS_MODULE,
> - .id_table = id_table,
> - .probe = virtblk_probe,
> - .remove = __devexit_p(virtblk_remove),
> + .feature_table = features,
> + .feature_table_size = ARRAY_SIZE(features),
> + .driver.name = KBUILD_MODNAME,
> + .driver.owner = THIS_MODULE,
> + .id_table = id_table,
> + .probe = virtblk_probe,
> + .remove = __devexit_p(virtblk_remove),
> + .config_changed = virtblk_config_changed,
> };
>
> static int __init init(void)
> {
> + int error;
> +
> + virtblk_wq = alloc_workqueue("md_misc", 0, 0);
> + if (!virtblk_wq)
> + return -ENOMEM;
> +
> major = register_blkdev(0, "virtblk");
> - if (major < 0)
> - return major;
> - return register_virtio_driver(&virtio_blk);
> + if (major < 0) {
> + error = major;
> + goto out_destroy_workqueue;
> + }
> +
> + error = register_virtio_driver(&virtio_blk);
> + if (error)
> + goto out_unregister_blkdev;
> + return 0;
> +
> +out_unregister_blkdev:
> + unregister_blkdev(major, "virtblk");
> +out_destroy_workqueue:
> + destroy_workqueue(virtblk_wq);
> + return error;
> }
>
> static void __exit fini(void)
> {
> unregister_blkdev(major, "virtblk");
> unregister_virtio_driver(&virtio_blk);
> + destroy_workqueue(virtblk_wq);
> }
> module_init(init);
> module_exit(fini);
> --
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