linux-kernel - Re: [PATCH v2] sunrpc: set the bv_offset of first bvec in svc_tcp

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Message-ID: <ZNp5nzfLGij7O5/k@tissot.1015granger.net>
Date:   Mon, 14 Aug 2023 14:59:43 -0400
From:   Chuck Lever <chuck.lever@...cle.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     David Howells <dhowells@...hat.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>, Neil Brown <neilb@...e.de>,
        Olga Kornievskaia <kolga@...app.com>,
        Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-nfs@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sunrpc: set the bv_offset of first bvec in
 svc_tcp_sendmsg

On Mon, Aug 14, 2023 at 01:36:54PM -0400, Jeff Layton wrote:
> svc_tcp_sendmsg used to factor in the xdr->page_base when sending pages,
> but 5df5dd03a8f7 dropped that part of the handling. Fix it by setting
> the bv_offset of the first bvec.
> 
> Fixes: 5df5dd03a8f7 ("sunrpc: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage")
> Signed-off-by: Jeff Layton <jlayton@...nel.org>

LGTM. However, nfsd-fixes does not have 5df5dd03a8f7 because the
previous nfsd-next was merged into v6.5 before David's
MSG_SPLICE_PAGES work was merged.

Unless someone has a better suggestion, I'll rebase nfsd-fixes to
v6.5-r6 and apply this fix to send to Linus.


> ---
> Changes in v2:
> - limit the change to just svc_tcp_sendmsg
> ---
>  net/sunrpc/svcsock.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index e43f26382411..2eb8df44f894 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1244,6 +1244,9 @@ static int svc_tcp_sendmsg(struct socket *sock, struct xdr_buf *xdr,
>  	if (ret != head->iov_len)
>  		goto out;
>  
> +	if (xdr_buf_pagecount(xdr))
> +		xdr->bvec[0].bv_offset = offset_in_page(xdr->page_base);
> +
>  	msg.msg_flags = MSG_SPLICE_PAGES;
>  	iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, xdr->bvec,
>  		      xdr_buf_pagecount(xdr), xdr->page_len);
> 
> ---
> base-commit: 2ccdd1b13c591d306f0401d98dedc4bdcd02b421
> change-id: 20230814-sendpage-b04874eed249
> 
> Best regards,
> -- 
> Jeff Layton <jlayton@...nel.org>
> 

-- 
Chuck Lever