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 <20201208202925.597663-2-Anna.Schumaker@Netapp.com> <2A6797DD-246D-4994-B38C-57AA0196D061@oracle.com>
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From:   Anna Schumaker <schumaker.anna@gmail.com>
Date:   Tue, 8 Dec 2020 16:11:28 -0500
Message-ID: <CAFX2JfkNO9LL_iaRE_RGjP+BHKiZGk8Eedg88_MKkuZUAysThw@mail.gmail.com>
Subject: Re: [PATCH v2 1/2] SUNRPC: Keep buf->len in sync with xdr->nwords
 when expanding holes
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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On Tue, Dec 8, 2020 at 3:56 PM Chuck Lever <chuck.lever@oracle.com> wrote:
>
>
>
> > On Dec 8, 2020, at 3:29 PM, schumaker.anna@gmail.com wrote:
> >
> > From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> >
> > Otherwise we could end up placing data a few bytes off from where we
> > actually want to put it.
> >
> > Fixes: 84ce182ab85b "SUNRPC: Add the ability to expand holes in data pages"
> > Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > ---
> > net/sunrpc/xdr.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
> > index 71e03b930b70..5b848fe65c81 100644
> > --- a/net/sunrpc/xdr.c
> > +++ b/net/sunrpc/xdr.c
> > @@ -1314,6 +1314,7 @@ uint64_t xdr_expand_hole(struct xdr_stream *xdr, uint64_t offset, uint64_t lengt
> >               unsigned int res = _shift_data_right_tail(buf, from + bytes - shift, shift);
> >               truncated = shift - res;
> >               xdr->nwords -= XDR_QUADLEN(truncated);
> > +             buf->len -= 4 * XDR_QUADLEN(truncated);
>
> If I understand what you're doing here correctly, the usual idiom
> is "XDR_QUADLEN(truncated) << 2" .

Oh, that works too. I'll adjust the patch. Thanks for letting me know!

Anna

>
>
> >               bytes -= shift;
> >       }
> >
> > @@ -1325,7 +1326,7 @@ uint64_t xdr_expand_hole(struct xdr_stream *xdr, uint64_t offset, uint64_t lengt
> >                                       bytes);
> >       _zero_pages(buf->pages, buf->page_base + offset, length);
> >
> > -     buf->len += length - (from - offset) - truncated;
> > +     buf->len += length - (from - offset);
> >       xdr_set_page(xdr, offset + length, PAGE_SIZE);
> >       return length;
> > }
> > --
> > 2.29.2
> >
>
> --
> Chuck Lever
>
>
>