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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0CDEC433FE for ; Mon, 10 Jan 2022 15:01:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 64D106B0074; Mon, 10 Jan 2022 10:01:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5FB856B0075; Mon, 10 Jan 2022 10:01:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 49D556B0078; Mon, 10 Jan 2022 10:01:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 38DC86B0074 for ; Mon, 10 Jan 2022 10:01:56 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id EA89718209A8A for ; Mon, 10 Jan 2022 15:01:55 +0000 (UTC) X-FDA: 79014692190.24.91EFD13 Received: from mail-qv1-f54.google.com (mail-qv1-f54.google.com [209.85.219.54]) by imf01.hostedemail.com (Postfix) with ESMTP id 7BDA040021 for ; Mon, 10 Jan 2022 15:01:55 +0000 (UTC) Received: by mail-qv1-f54.google.com with SMTP id r6so14639675qvr.13 for ; Mon, 10 Jan 2022 07:01:55 -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; bh=aWYOlhNv94zvH8vQr6oOqvsObY+YoaIX9r8fry3TfgU=; b=o3yGW4RN1VoHyvVMABl2JA3OlnZAnFrtLwDfuY1vxst2Owcy+yFQdBuVXgFgQG/Yp+ aIEFX/j3dAqI42643RqkJomWtRA0BDDSRGx2x8Hv/GAQinoerAOb9ijBMPPpPEza/2ko kMrC0KgB6Pu0Nj+HlrFp0xS0UaxDg0I6NB+PWTpH62Rh09rR+7G8lGHnK3poPYucogj2 Zk0okqme/tUI+MY+BxgyPqdeEMUdF6+LLaSCVl0eioCmC/kalgXRxrGkiYuCNLTBv5md /LjoZA7xfHSoKcZrBon5j5/xyZAFAcMlnu8Jrtcoyj+5A37229e/OPxtLqvCJ+UDtrvk IobQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=aWYOlhNv94zvH8vQr6oOqvsObY+YoaIX9r8fry3TfgU=; b=q/hKJdlvCmx0ui8TzJeDC8aMDftibPkNuO4Tkg70YFLVPAAxYKFvqS/5hLkgK7vSD+ 5sOPtA4uQYUQdPjLbEdw3LzZ6Ool/Wm7zo2nFvEYff05otdQsjladnZ/TuUiIW19erQT ijoR2pj4Ka36H5Igx94pQfMYJQ0d7prOLgkeh4odAcwSkhlbptdf1QS89qWD8GKuWYVB YcTqNlD0vpZRWSx/m6DwL/0X0IBeMhUpPr+FNJW9cvX+bONNvIoaa1r3dvzIHT8Ejqvn 2oo/QpQfqNHzQDwvHaHGKvC/08BhP+QIO8lH5crh/C5/NIQXySo7QrGNrzJwg0n+/F9K gkAw== X-Gm-Message-State: AOAM531rUvacL4h/vM8qBkt0qM7nMlU0xZqq1OLmXF903OOB2+vMGGai YE5uw7RfLQtoce2JtFyECVMngw== X-Google-Smtp-Source: ABdhPJzNKTCfAbCzHYScQrP2SHt5CHcZ9icO6LkmRIqro4Up34V0TSXW1GuGsePOwEkkPqGN8p0vYw== X-Received: by 2002:a05:6214:29ea:: with SMTP id jv10mr4321076qvb.105.1641826914763; Mon, 10 Jan 2022 07:01:54 -0800 (PST) Received: from ziepe.ca (hlfxns017vw-142-162-113-129.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.113.129]) by smtp.gmail.com with ESMTPSA id t3sm5144934qtc.7.2022.01.10.07.01.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Jan 2022 07:01:54 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1n6wBF-00DodR-E9; Mon, 10 Jan 2022 11:01:53 -0400 Date: Mon, 10 Jan 2022 11:01:53 -0400 From: Jason Gunthorpe To: Matthew Wilcox Cc: John Hubbard , linux-mm@kvack.org, Andrew Morton Subject: Re: [PATCH 05/17] gup: Add try_get_folio() Message-ID: <20220110150153.GG6467@ziepe.ca> References: <20220102215729.2943705-1-willy@infradead.org> <20220102215729.2943705-6-willy@infradead.org> <3ac8af50-dff6-4a0f-dba6-8b8fe5f611d4@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 7BDA040021 X-Stat-Signature: zapahtu4ptmf949q4nao5u8ogdi39g5o Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=ziepe.ca header.s=google header.b=o3yGW4RN; dmarc=none; spf=pass (imf01.hostedemail.com: domain of jgg@ziepe.ca designates 209.85.219.54 as permitted sender) smtp.mailfrom=jgg@ziepe.ca X-HE-Tag: 1641826915-964749 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: On Sat, Jan 08, 2022 at 01:37:09AM +0000, Matthew Wilcox wrote: > I think there is sufficient protection; either we have interrupts > disabled in gup-fast (which prevents RCU from finishing a grace > period), or we have the mmap_sem held in gup-slow (which prevents > pages from being removed from the page tables). mmap sem doesn't prevent pages from being removed, for instance unmap_mapping_pages() doesn't hold it. It is safe because gup slow holds the PTLs when it calls this. No idea about how the get_gate_page() works Jason