From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: iSER initiator in 4.5 is unhappy.. Date: Thu, 7 Apr 2016 08:20:12 -0700 Message-ID: <20160407152012.GA10297@infradead.org> References: <5702A46F.5070109@grimberg.me> <5702A6AC.9020008@grimberg.me> <20160404225831.GA6725@infradead.org> <57037D8E.4030506@grimberg.me> <20160405094339.GA1622@infradead.org> <570548AB.4090802@grimberg.me> <20160406231658.GB11588@infradead.org> <570608C9.1070805@grimberg.me> <570623B9.8040108@mellanox.com> <570679B6.10409@grimberg.me> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <570679B6.10409-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sagi Grimberg Cc: Max Gurtovoy , Christoph Hellwig , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On Thu, Apr 07, 2016 at 06:16:06PM +0300, Sagi Grimberg wrote: > >>segment (which results in an extra page). The patch should fix the > >>problem, however in this particular sg list I don't see the violation > >>(counted 127 pages)... > > > >I counted 129 pages. > >I will run some tests in our labs too. > > If you did then that indicates the block layer violates > its obligation to respect max_segments/max_hw_sectors? I spent some time looking over the code and remembered an issue I fixed for NVMf (which might explain why we're not seeing it there). max_segments just means contiguous segments, not nessecarily 4k pages. For that we either need a small enough max_sectors_hw or set a max_segment_size of 4k, otherwise we might get 128 block segments, but due to lacking alignment they'll expand to 129 pages. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html