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

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Message-ID: <CAPXgP100NjPw4JVe39gL829MwKL2YLFSKN2fvaB7skbCub-Ehg@mail.gmail.com>
Date:	Tue, 26 Feb 2013 00:04:15 +0100
From:	Kay Sievers <kay@...y.org>
To:	Greg KH <greg@...ah.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Milos Vyletel <milos.vyletel@....cz>,
	linux-kernel@...r.kernel.org, linux-hotplug@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, mst@...hat.com
Subject: Re: [PATCH] virtio-blk: emit udev event when device is resized

On Mon, Feb 25, 2013 at 11:43 PM, Greg KH <greg@...ah.com> wrote:
> On Mon, Feb 25, 2013 at 11:39:52PM +0100, Kay Sievers wrote:
>> On Mon, Feb 25, 2013 at 11:12 PM, Greg KH <greg@...ah.com> wrote:
>>
>> > Hm, I thought we were frowning apon running binaries from udev rules
>> > these days, especially ones that might have big consequences (like
>> > resizing a disk image) like this.
>> >
>> > Kay, am I right?
>>
>> We removed most of them from the default setups, yes. But there is
>> nothing wrong if people want to ship that in some package or as custom
>> rules.
>>
>> It looks fine to me, we would just not add such things to the default
>> set of of rules these days.
>>
>> > We already emit KOBJECT_CHANGE events when block devices change, from
>> > within the block core code.  Why is the patch below needed instead of
>> > using these events that are already generated?  How are virtio block
>> > devices special?
>>
>> I think we only do that for dm and md and a couple of special cases
>> like loop and read-only settings.
>
> What about when we repartition a block device?  I've seen the events
> happen then.

Right, from the common block code we send events for removable media
changes like cdroms, sd cards, when a device is switched to read-only,
and when we re-scan a partition table like on re-partitioning. Most of
the other events are block subsystem-specific like this one. For
things like device-mapper they are used pretty heavily.

> Anyway, if you are ok with this, no objection from my side then Rusty.

Looks fine to me, it should not do any harm if there are not heavy
programs hooked up -- which is nothing the kernel could fix if people
do that. :)

Kay
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