linux-kernel - Re: [PATCH] nbd: Zero from and len fields in NBD_CMD

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Message-ID: <20140518091113.GA3770@Inspiron-3521>
Date:	Sun, 18 May 2014 10:11:13 +0100
From:	Hani Benhabiles <kroosec@...il.com>
To:	Paul Clements <paul.clements@...sios.com>
Cc:	"nbd-general@...ts.sourceforge.net" 
	<nbd-general@...ts.sourceforge.net>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nbd: Zero from and len fields in NBD_CMD_DISCONNECT.

On Fri, May 16, 2014 at 10:56:33PM -0400, Paul Clements wrote:
> Agreed. But better yet, the request structure should just be zeroed when
> it's allocated.
> 

It is already initialized  in __nbd_ioctl() with the blk_rq_init() call which
sets the __sector value to -1 (which is 0xfffffffffffffe00 after the left shifts.)

This is the only (non-ugly / non-intrusive) way to do it afaict.

> --
> Paul
> 
> 
> On Fri, May 16, 2014 at 7:43 PM, Hani Benhabiles <kroosec@...il.com> wrote:
> 
> > Len field is already set to zero, but not the from field which is sent as
> > 0xfffffffffffffe00. This makes no sense, and may cause confuse server
> > implementations doing sanity checks (qemu-nbd is an example.)
> >
> > Signed-off-by: Hani Benhabiles <hani@...ux.com>
> > ---
> >  drivers/block/nbd.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> > index 3a70ea2..657bdac 100644
> > --- a/drivers/block/nbd.c
> > +++ b/drivers/block/nbd.c
> > @@ -246,7 +246,7 @@ static int nbd_send_req(struct nbd_device *nbd, struct
> > request *req)
> >         request.magic = htonl(NBD_REQUEST_MAGIC);
> >         request.type = htonl(nbd_cmd(req));
> >
> > -       if (nbd_cmd(req) == NBD_CMD_FLUSH) {
> > +       if (nbd_cmd(req) == NBD_CMD_FLUSH || nbd_cmd(req) == NBD_CMD_DISC)
> > {
> >                 /* Other values are reserved for FLUSH requests.  */
> >                 request.from = 0;
> >                 request.len = 0;
> > --
> > 1.8.3.2
> >
> >
--
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