linux-kernel - Re: [PATCH] blkfront: add uevent for size change

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Message-ID: <20170412000528.GA13555@amazon.com>
Date:   Tue, 11 Apr 2017 17:05:28 -0700
From:   Marc Olson <marcolso@...zon.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:     <xen-devel@...ts.xenproject.org>,
        Roger Pau Monné <roger.pau@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        "David Vrabel" <david.vrabel@...rix.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] blkfront: add uevent for size change

On Tue, Apr 11, 2017 at 04:04:59PM -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, Apr 11, 2017 at 12:24:09PM -0700, Marc Olson wrote:
> > When a blkfront device is resized from dom0, emit a KOBJ_CHANGE uevent to
> > notify the guest about the change. This allows for custom udev rules, such
> > as automatically resizing a filesystem, when an event occurs.
> 
> Looks pretty reasonable.
> 
> Could you confirm what the udevadm --monitor --kernel --udev emits when this happens?

Relevant output:

KERNEL[577.206230] change   /devices/vbd-51728/block/xvdb (block)
UDEV  [577.226218] change   /devices/vbd-51728/block/xvdb (block)

Of course, this is missing without the patch.

/marc

> 
> Thanks!
> 
> > 
> > Signed-off-by: Marc Olson <marcolso@...zon.com>
> > ---
> >  drivers/block/xen-blkfront.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> > index 2fee2ee..66abf9c 100644
> > --- a/drivers/block/xen-blkfront.c
> > +++ b/drivers/block/xen-blkfront.c
> > @@ -1996,6 +1996,7 @@ static void blkfront_connect(struct blkfront_info *info)
> >  	unsigned long sector_size;
> >  	unsigned int physical_sector_size;
> >  	unsigned int binfo;
> > +	char *envp[] = { "RESIZE=1", NULL };
> >  	int err;
> >  
> >  	switch (info->connected) {
> > @@ -2012,6 +2013,8 @@ static void blkfront_connect(struct blkfront_info *info)
> >  		       sectors);
> >  		set_capacity(info->gd, sectors);
> >  		revalidate_disk(info->gd);
> > +		kobject_uevent_env(&disk_to_dev(info->gd)->kobj,
> > +				   KOBJ_CHANGE, envp);
> >  
> >  		return;
> >  	case BLKIF_STATE_SUSPENDED:
> > -- 
> > 2.7.4
> > 
>