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

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Message-ID: <CAECXXi69w4HNUbZbb3JWxwZkqnyQf=dmm57UJEHOY0Xv6B4pEA@mail.gmail.com>
Date:	Sun, 25 May 2014 14:11:13 -0400
From:	Paul Clements <paul.clements@...sios.com>
To:	Hani Benhabiles <kroosec@...il.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 Sun, May 25, 2014 at 6:18 AM, Hani Benhabiles <kroosec@...il.com> wrote:
> On Sun, May 18, 2014 at 10:11:13AM +0100, Hani Benhabiles wrote:
>> 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.
>>
>
> Ping!
>
> Anything blocking this patch ?

It's cleaner to just zero the struct and get rid of the conditional
zeroing of specific fields. I'll prepare a patch in the next few days.

Thanks,
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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