From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: Re: [PATCH v1 10/10] svcrdma: Handle additional inline content Date: Tue, 13 Jan 2015 12:11:41 +0200 Message-ID: <54B4EF5D.3040201@dev.mellanox.co.il> References: <20150109191910.4901.29548.stgit@klimt.1015granger.net> <20150109192319.4901.89444.stgit@klimt.1015granger.net> <54B2BA77.20101@dev.mellanox.co.il> <46D2849E-39D7-4290-91CE-FD66E3F96B21@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <46D2849E-39D7-4290-91CE-FD66E3F96B21-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Chuck Lever Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux NFS Mailing List List-Id: linux-rdma@vger.kernel.org On 1/12/2015 3:13 AM, Chuck Lever wrote: > > On Jan 11, 2015, at 1:01 PM, Sagi Grimberg = wrote: > >> On 1/9/2015 9:23 PM, Chuck Lever wrote: >>> Most NFS RPCs place large payload arguments at the end of the RPC >>> header (eg, NFSv3 WRITE). For NFSv3 WRITE and SYMLINK, RPC/RDMA >>> sends the complete RPC header inline, and the payload argument in a >>> read list. >>> >>> One important case is not like this, however. NFSv4 WRITE compounds >>> can have an operation after the WRITE operation. The proper way to >>> convey an NFSv4 WRITE is to place the GETATTR inline, but _after_ >>> the read list position. (Note Linux clients currently do not do >>> this, but they will be changed to do it in the future). >>> >>> The receiver could put trailing inline content in the XDR tail >>> buffer. But the Linux server's NFSv4 compound processing does not >>> consider the XDR tail buffer. >>> >>> So, move trailing inline content to the end of the page list. This >>> presents the incoming compound to upper layers the same way the >>> socket code does. >>> >> >> Would this memcpy be saved if you just posted a larger receive buffe= r >> and the client would used it "really inline" as part of it's post_se= nd? > > The receive buffer doesn=92t need to be larger. Clients already shoul= d > construct this trailing inline content in their SEND buffers. > > Not that the Linux client doesn=92t yet send the extra inline via RD= MA > SEND, it uses a separate RDMA READ to move the extra bytes, and that=92= s > a bug. > > If the client does send this inline as it=92s supposed to, the server > would receive it in its pre-posted RECV buffer. This patch simply > moves that content into the XDR buffer page list, where the server=92= s > XDR decoder can find it. Would it make more sense to manipulate pointers instead of copying data= ? But if this is only 16 bytes than maybe it's not worth the trouble... -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html