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[142.162.113.180]) by smtp.gmail.com with ESMTPSA id t65sm8907102qkh.23.2019.11.04.18.32.36 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 04 Nov 2019 18:32:36 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1iRoe3-0002uH-K9; Mon, 04 Nov 2019 22:32:35 -0400 Date: Mon, 4 Nov 2019 22:32:35 -0400 From: Jason Gunthorpe To: John Hubbard Subject: Re: [PATCH v2 07/18] infiniband: set FOLL_PIN, FOLL_LONGTERM via pin_longterm_pages*() Message-ID: <20191105023235.GA11093@ziepe.ca> References: <20191103211813.213227-1-jhubbard@nvidia.com> <20191103211813.213227-8-jhubbard@nvidia.com> <20191104203346.GF30938@ziepe.ca> <578c1760-7221-4961-9f7d-c07c22e5c259@nvidia.com> <20191104205738.GH30938@ziepe.ca> <1560fa00-0c2b-0f3b-091c-d628f021ce09@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1560fa00-0c2b-0f3b-091c-d628f021ce09@nvidia.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Hocko , Jan Kara , kvm@vger.kernel.org, linux-doc@vger.kernel.org, David Airlie , Dave Chinner , dri-devel@lists.freedesktop.org, LKML , linux-mm@kvack.org, Paul Mackerras , linux-kselftest@vger.kernel.org, Ira Weiny , Jonathan Corbet , linux-rdma@vger.kernel.org, Christoph Hellwig , Vlastimil Babka , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , linux-media@vger.kernel.org, Shuah Khan , linux-block@vger.kernel.org, =?utf-8?B?SsOpcsO0bWU=?= Glisse , Al Viro , Dan Williams , Mauro Carvalho Chehab , bpf@vger.kernel.org, Magnus Karlsson , Jens Axboe , netdev@vger.kernel.org, Alex Williamson , Daniel Vetter , linux-fsdevel@vger.kernel.org, Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S . Miller" , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Nov 04, 2019 at 02:03:43PM -0800, John Hubbard wrote: > On 11/4/19 12:57 PM, Jason Gunthorpe wrote: > > On Mon, Nov 04, 2019 at 12:48:13PM -0800, John Hubbard wrote: > >> On 11/4/19 12:33 PM, Jason Gunthorpe wrote: > >> ... > >>>> diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c > >>>> index 24244a2f68cc..c5a78d3e674b 100644 > >>>> +++ b/drivers/infiniband/core/umem.c > >>>> @@ -272,11 +272,10 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr, > >>>> > >>>> while (npages) { > >>>> down_read(&mm->mmap_sem); > >>>> - ret = get_user_pages(cur_base, > >>>> + ret = pin_longterm_pages(cur_base, > >>>> min_t(unsigned long, npages, > >>>> PAGE_SIZE / sizeof (struct page *)), > >>>> - gup_flags | FOLL_LONGTERM, > >>>> - page_list, NULL); > >>>> + gup_flags, page_list, NULL); > >>> > >>> FWIW, this one should be converted to fast as well, I think we finally > >>> got rid of all the blockers for that? > >>> > >> > >> I'm not aware of any blockers on the gup.c end, anyway. The only broken thing we > >> have there is "gup remote + FOLL_LONGTERM". But we can do "gup fast + LONGTERM". > > > > I mean the use of the mmap_sem here is finally in a way where we can > > just delete the mmap_sem and use _fast > > > > ie, AFAIK there is no need for the mmap_sem to be held during > > ib_umem_add_sg_table() > > > > This should probably be a standalone patch however > > > > Yes. Oh, actually I guess the patch flow should be: change to > get_user_pages_fast() and remove the mmap_sem calls, as one patch. And then change > to pin_longterm_pages_fast() as the next patch. Otherwise, the internal fallback > from _fast to slow gup would attempt to take the mmap_sem (again) in the same > thread, which is not good. :) > > Or just defer the change until after this series. Either way is fine, let me > know if you prefer one over the other. > > The patch itself is trivial, but runtime testing to gain confidence that > it's solid is much harder. Is there a stress test you would recommend for that? > (I'm not promising I can quickly run it yet--my local IB setup is still nascent > at best.) If you make a patch we can probably get it tested, it is something we should do I keep forgetting about. Jason