linux-kernel - Re: [PATCH] virtio-blk: emit udev event when device is resized

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Message-ID: <87vc9eegn3.fsf@rustcorp.com.au>
Date:	Wed, 27 Feb 2013 11:07:20 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Milos Vyletel <milos.vyletel@....cz>, linux-kernel@...r.kernel.org
Cc:	virtualization@...ts.linux-foundation.org, mst@...hat.com,
	Asias He <asias@...hat.com>
Subject: Re: [PATCH] virtio-blk: emit udev event when device is resized

Milos Vyletel <milos.vyletel@....cz> writes:

> When virtio-blk device is resized from host (using block_resize from QEMU) emit
> KOBJ_CHANGE uevent to notify guest about such change. This allows user to have
> custom udev rules which would take whatever action if such event occurs. As a
> proof of concept I've created simple udev rule that automatically resize
> filesystem on virtio-blk device.
>
> ACTION=="change", KERNEL=="vd*", \
>         ENV{RESIZE}=="1", \
>         ENV{ID_FS_TYPE}=="ext[3-4]", \
>         RUN+="/sbin/resize2fs /dev/%k"
> ACTION=="change", KERNEL=="vd*", \
>         ENV{RESIZE}=="1", \
>         ENV{ID_FS_TYPE}=="LVM2_member", \
>         RUN+="/sbin/pvresize /dev/%k"
>
> Signed-off-by: Milos Vyletel <milos.vyletel@....cz>

OK, I collapsed the event[] line as suggested by Asias, and applied this.

Thanks,
Rusty.

From: Milos Vyletel <milos.vyletel@....cz>
Subject: virtio-blk: emit udev event when device is resized

When virtio-blk device is resized from host (using block_resize from QEMU) emit
KOBJ_CHANGE uevent to notify guest about such change. This allows user to have
custom udev rules which would take whatever action if such event occurs. As a
proof of concept I've created simple udev rule that automatically resize
filesystem on virtio-blk device.

ACTION=="change", KERNEL=="vd*", \
        ENV{RESIZE}=="1", \
        ENV{ID_FS_TYPE}=="ext[3-4]", \
        RUN+="/sbin/resize2fs /dev/%k"
ACTION=="change", KERNEL=="vd*", \
        ENV{RESIZE}=="1", \
        ENV{ID_FS_TYPE}=="LVM2_member", \
        RUN+="/sbin/pvresize /dev/%k"

Signed-off-by: Milos Vyletel <milos.vyletel@....cz>
Tested-by: Asias He <asias@...hat.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au> (minor simplification)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 8ad21a2..922bcb9 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -539,6 +539,7 @@ static void virtblk_config_changed_work(struct work_struct *work)
 	struct virtio_device *vdev = vblk->vdev;
 	struct request_queue *q = vblk->disk->queue;
 	char cap_str_2[10], cap_str_10[10];
+	char *envp[] = { "RESIZE=1", NULL };
 	u64 capacity, size;
 
 	mutex_lock(&vblk->config_lock);
@@ -568,6 +569,7 @@ static void virtblk_config_changed_work(struct work_struct *work)
 
 	set_capacity(vblk->disk, capacity);
 	revalidate_disk(vblk->disk);
+	kobject_uevent_env(&disk_to_dev(vblk->disk)->kobj, KOBJ_CHANGE, envp);
 done:
 	mutex_unlock(&vblk->config_lock);
 }
--
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