From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF948C10F03 for ; Tue, 5 Mar 2019 00:53:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC4DB20675 for ; Tue, 5 Mar 2019 00:53:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="cIbA4txX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726887AbfCEAxm (ORCPT ); Mon, 4 Mar 2019 19:53:42 -0500 Received: from mail-qt1-f196.google.com ([209.85.160.196]:33706 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726066AbfCEAxm (ORCPT ); Mon, 4 Mar 2019 19:53:42 -0500 Received: by mail-qt1-f196.google.com with SMTP id z39so7301397qtz.0 for ; Mon, 04 Mar 2019 16:53:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=XVYt//8tLSfx+WH6Lmq9iHXTEUimc3qP6GGB8yuMZP4=; b=cIbA4txXePxhYRMosF0K4Lf0pYeh5EsSFPuqs/QO/VWfnll6mD6fAdE5bLAsxDDV8b pMcaqaJ3cAphmez5ynHwcu+nAOnX0lNGpa7CfwAzx/1IBdJnNYHnEs0njSfozkQkDnv/ /BDWuTYiFElCsWZmnR2f6Eftcm3hsGd/oyx8aEzIscAlTcejvxOn6sJPgios4EMa8IiL l4INWPvsR6ZjJr6mAb5ZQR8azH8ilI7Fvz8bLkbr+OXB0/VIqrZFmE581eaxUEa3760i o773UgVIyzIPBn4hPNDtc3ZZbNSV3pZYH07dyPgrK9oDQdUm6/M/bazP0dozLWDejXAZ kJEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=XVYt//8tLSfx+WH6Lmq9iHXTEUimc3qP6GGB8yuMZP4=; b=cNzf7beVUWM19WPI4mY4mPuItwTOKR+ioVh7VfLUpGsKkY/p5qeYBIO+ePmLPw/kVW qO8DT6kJ4ihJjLotFh/ZSJgKcQg/XUOjYQ0psGGGdVo3QJVmcHuknk0/dZOXJzKBD0Y0 pdgr7f8RQZRhQnwDW++WJE1LXHUiejsGUesTev0bnru1DtYtZkt3kezNWFNvTptmGVpC 6mXOhZYDrWQbIsVrVjFkHQjsaunj791YimGdr/VIGAOixC1x5MtYekNpJQ6DJSnoEEKL +0SqzGPEmUlnu7r9gJ0EG9daRV95WxUFYHsm5H4gchHwhXcYbk2hErdxKbUmZyGilwqW /QaQ== X-Gm-Message-State: APjAAAUzU1CrbRjHBorR67mrqSZqNHPajed3SB66qtGLEorfy+2NFCJq HkcaDq0IsLpybRIZcrSNXwKyUg== X-Google-Smtp-Source: APXvYqwgYquIrGrypPfGh12coX509Dw+mf6crd2NMr+KYucqtQsXeX7lvPZECuSr4ZCtq072yEeFpw== X-Received: by 2002:ac8:2b2e:: with SMTP id 43mr16897084qtu.33.1551747221098; Mon, 04 Mar 2019 16:53:41 -0800 (PST) Received: from ziepe.ca ([24.137.65.181]) by smtp.gmail.com with ESMTPSA id d80sm4140972qkg.83.2019.03.04.16.53.39 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 04 Mar 2019 16:53:40 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1h0yKw-0002jB-Vl; Mon, 04 Mar 2019 20:53:38 -0400 Date: Mon, 4 Mar 2019 20:53:38 -0400 From: Jason Gunthorpe To: John Hubbard Cc: Ira Weiny , Artemy Kovalyov , "john.hubbard@gmail.com" , "linux-mm@kvack.org" , Andrew Morton , LKML , Doug Ledford , "linux-rdma@vger.kernel.org" Subject: Re: [PATCH v2] RDMA/umem: minor bug fix and cleanup in error handling paths Message-ID: <20190305005338.GK8613@ziepe.ca> References: <20190302032726.11769-2-jhubbard@nvidia.com> <20190302202435.31889-1-jhubbard@nvidia.com> <20190302194402.GA24732@iweiny-DESK2.sc.intel.com> <2404c962-8f6d-1f6d-0055-eb82864ca7fc@mellanox.com> <20190303165550.GB27123@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 04, 2019 at 03:11:05PM -0800, John Hubbard wrote: > get_user_page(): increments page->_refcount by a large amount (1024) > > put_user_page(): decrements page->_refcount by a large amount (1024) > > ...and just stop doing the odd (to me) technique of incrementing once for > each tail page. I cannot see any reason why that's actually required, as > opposed to just "raise the page->_refcount enough to avoid losing the head > page too soon". I'd very much like to see this in the infiniband umem code - the extra work and cost of touching every page in a huge page is very much undesired. Jason