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Date:   Sat, 5 Dec 2020 11:29:05 +0200
From:   Dan Aloni <dan@kernelim.com>
To:     Trond Myklebust <trondmy@hammerspace.com>
Cc:     "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH] sunrpc: fix xs_read_xdr_buf for partial pages receive
Message-ID: <20201205092905.GA1943555@gmail.com>
References: <20201204183419.1532347-1-dan@kernelim.com>
 <528fd4a869f0757e0a60e9c733d4625067693588.camel@hammerspace.com>
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On Fri, Dec 04, 2020 at 08:52:55PM +0000, Trond Myklebust wrote:
> On Fri, 2020-12-04 at 20:34 +0200, Dan Aloni wrote:
[..]
> > --- a/net/sunrpc/xprtsock.c
> > +++ b/net/sunrpc/xprtsock.c
> > @@ -436,7 +436,7 @@ xs_read_xdr_buf(struct socket *sock, struct
> > msghdr *msg, int flags,
> > ????????????????offset += ret - buf->page_base;
> > ????????????????if (offset == count || msg->msg_flags &
> > (MSG_EOR|MSG_TRUNC))
> > ????????????????????????goto out;
> > -???????????????if (ret != want)
> > +???????????????if (ret - buf->page_base != want)
> > ????????????????????????goto out;
> > ????????????????seek = 0;
> > ????????} else {
> 
> Ouch... Well spotted!
> 
> Hmm... I think we want to just subtract out the buf->page_base from the
> value of 'ret' after we call xs_flush_bvec() and then adjust the
> calculation of 'offset' in the next line. That's more efficient.

Yes, it works out, though after being aware that the positive value of
`ret` when returned from `xs_read_xdr_buf` and propagated upward has no
effect except on traces.

-- 
Dan Aloni