From mboxrd@z Thu Jan 1 00:00:00 1970 From: 'Christoph Hellwig' Subject: Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags Date: Tue, 14 Jul 2015 12:45:12 -0700 Message-ID: <20150714194512.GA25887@infradead.org> References: <20150708190842.GB11740@obsidianresearch.com> <20150708203205.GA21847@infradead.org> <20150709000337.GE16812@obsidianresearch.com> <559EF332.7060103@redhat.com> <20150709225306.GA30741@obsidianresearch.com> <559FC710.1050307@talpey.com> <20150710161108.GA19042@obsidianresearch.com> <55A24571.60902@dev.mellanox.co.il> <00e201d0be6a$e49bc910$add35b30$@opengridcomputing.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <00e201d0be6a$e49bc910$add35b30$@opengridcomputing.com> Sender: target-devel-owner@vger.kernel.org To: Steve Wise Cc: 'Sagi Grimberg' , 'Steve Wise' , 'Jason Gunthorpe' , 'Tom Talpey' , 'Doug Ledford' , 'Christoph Hellwig' , sagig@mellanox.com, ogerlitz@mellanox.com, roid@mellanox.com, linux-rdma@vger.kernel.org, eli@mellanox.com, target-devel@vger.kernel.org, linux-nfs@vger.kernel.org, trond.myklebust@primarydata.com, bfields@fieldses.org, 'Oren Duer' List-Id: linux-rdma@vger.kernel.org On Tue, Jul 14, 2015 at 02:25:50PM -0500, Steve Wise wrote: > if (device_supports_fastreg && device_supports_signature) > use FRMR > else > use DMAMR > > Shouldn't we just recode it this way? > > if (device_supports_fastreg) > use FRMR > else > use DMAMR How does IB_DEVICE_LOCAL_DMA_LKEY (and ->local_dma_lkey) play into this? Seems like that should be the preferred option if supported. Interestingly enough various iWarp driver seem to support this option, what's the story behind that? The (to me surprising) conclusion on the list was that iWarp would always need a memory regireations that also allows remove writes even for lkeys, but from looking at the users of IB_DEVICE_LOCAL_DMA_LKEY / local_dma_lkey that seem to prefer that over creating a MR.