From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: Re: [PATCH V3] svcrdma: advertise the correct max payload Date: Wed, 24 Sep 2014 14:55:56 +0300 Message-ID: <5422B14C.3040502@dev.mellanox.co.il> References: <20140923221122.24227.91718.stgit@build.ogc.int> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140923221122.24227.91718.stgit-T4OLL4TyM9aNDNWfRnPdfg@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Steve Wise , fields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On 9/24/2014 1:11 AM, Steve Wise wrote: > Svcrdma currently advertises 1MB, which is too large. The correct value > is the minimum of RPCSVC_MAXPAYLOAD and the max scatter-gather allowed > in an NFSRDMA IO chunk * the host page size. This bug is usually benign > because the Linux X64 NFSRDMA client correctly limits the payload size to > the correct value (64*4096 = 256KB). But if the Linux client is PPC64 > with a 64KB page size, then the client will indeed use a payload size > that will overflow the server. > Maybe I'm a bit late with this, but can you explain why SG table is limited to 64 (fastreg MR and page_list probably bound it). Where is it coming from? Naturally it needs to be bound by some figure, but why 64? Sorry if I'm nit-picking on this pretty straight-forward bug fix... Sagi. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html