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[213.133.104.62]) by mx.google.com with ESMTPS id x126si25476519wmx.2.2019.02.11.07.33.32 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 11 Feb 2019 07:33:32 -0800 (PST) Received-SPF: pass (google.com: domain of daniel@iogearbox.net designates 213.133.104.62 as permitted sender) client-ip=213.133.104.62; Authentication-Results: mx.google.com; spf=pass (google.com: domain of daniel@iogearbox.net designates 213.133.104.62 as permitted sender) smtp.mailfrom=daniel@iogearbox.net Received: from [78.46.172.3] (helo=sslproxy06.your-server.de) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1gtDaM-0007KE-6j; Mon, 11 Feb 2019 16:33:30 +0100 Received: from [2a02:1203:ecb1:b710:c81f:d2d6:50a9:c2d] (helo=linux.home) by sslproxy06.your-server.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1gtDaL-000Ow1-WC; Mon, 11 Feb 2019 16:33:30 +0100 Subject: Re: [PATCH 1/2] xsk: do not use mmap_sem To: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Davidlohr Bueso Cc: akpm@linux-foundation.org, linux-mm@kvack.org, LKML , "David S . Miller" , Bjorn Topel , Magnus Karlsson , Netdev , Davidlohr Bueso , dan.j.williams@intel.com References: <20190207053740.26915-1-dave@stgolabs.net> <20190207053740.26915-2-dave@stgolabs.net> From: Daniel Borkmann Message-ID: Date: Mon, 11 Feb 2019 16:33:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.100.2/25357/Mon Feb 11 11:38:50 2019) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: [ +Dan ] On 02/07/2019 08:43 AM, Björn Töpel wrote: > Den tors 7 feb. 2019 kl 06:38 skrev Davidlohr Bueso : >> >> Holding mmap_sem exclusively for a gup() is an overkill. >> Lets replace the call for gup_fast() and let the mm take >> it if necessary. >> >> Cc: David S. Miller >> Cc: Bjorn Topel >> Cc: Magnus Karlsson >> CC: netdev@vger.kernel.org >> Signed-off-by: Davidlohr Bueso >> --- >> net/xdp/xdp_umem.c | 6 ++---- >> 1 file changed, 2 insertions(+), 4 deletions(-) >> >> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c >> index 5ab236c5c9a5..25e1e76654a8 100644 >> --- a/net/xdp/xdp_umem.c >> +++ b/net/xdp/xdp_umem.c >> @@ -265,10 +265,8 @@ static int xdp_umem_pin_pages(struct xdp_umem *umem) >> if (!umem->pgs) >> return -ENOMEM; >> >> - down_write(¤t->mm->mmap_sem); >> - npgs = get_user_pages(umem->address, umem->npgs, >> - gup_flags, &umem->pgs[0], NULL); >> - up_write(¤t->mm->mmap_sem); >> + npgs = get_user_pages_fast(umem->address, umem->npgs, >> + gup_flags, &umem->pgs[0]); >> > > Thanks for the patch! > > The lifetime of the pinning is similar to RDMA umem mapping, so isn't > gup_longterm preferred? Seems reasonable from reading what gup_longterm seems to do. Davidlohr or Dan, any thoughts on the above? Thanks, Daniel