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 C8A80C433FE for ; Wed, 23 Nov 2022 13:26:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6B66C6B0071; Wed, 23 Nov 2022 08:26:24 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 63F636B0073; Wed, 23 Nov 2022 08:26:24 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4E1016B0074; Wed, 23 Nov 2022 08:26:24 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 381B06B0071 for ; Wed, 23 Nov 2022 08:26:24 -0500 (EST) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 077D681147 for ; Wed, 23 Nov 2022 13:26:24 +0000 (UTC) X-FDA: 80164781088.25.D7D6F7E Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf05.hostedemail.com (Postfix) with ESMTP id 60457100006 for ; Wed, 23 Nov 2022 13:26:22 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 394E2B81FC0; Wed, 23 Nov 2022 13:26:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CB42CC433C1; Wed, 23 Nov 2022 13:26:11 +0000 (UTC) Message-ID: <36dd800b-d96b-af39-d0de-a5a8ca1034dd@xs4all.nl> Date: Wed, 23 Nov 2022 14:26:10 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Content-Language: en-US To: David Hildenbrand , Tomasz Figa Cc: x86@kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, Linus Torvalds , Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit , Vlastimil Babka , Matthew Wilcox , Mike Kravetz , Muchun Song , Shuah Khan , Lucas Stach , David Airlie , Oded Gabbay , Arnd Bergmann , Christoph Hellwig , Alex Williamson , Marek Szyprowski , Mauro Carvalho Chehab , linux-kernel@vger.kernel.org References: <20221116102659.70287-1-david@redhat.com> <20221116102659.70287-17-david@redhat.com> From: Hans Verkuil Subject: Re: [PATCH mm-unstable v1 16/20] mm/frame-vector: remove FOLL_FORCE usage In-Reply-To: <20221116102659.70287-17-david@redhat.com> Content-Type: text/plain; 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bh=ncjZPWzUKnlSE26YFXwEwn/z3lsXD3zAtFfQ9CxCqM8=; b=DE41/oglWR0Yhc8xVl+HSPeELOW/FTQfXaiIY3t3hIxYCEbaN3JMWJZsJZIZCLIixH4l24 0QZPQX4z9t3+mWEF3lnBaq1teN2TMBYgvYl8Eanr5Hidnhw9nIiG21pT14RT9YuAV3fL/M dlWhAiZoF8cn7AUGzXpuXUXt7U3brQg= X-Rspam-User: X-Stat-Signature: arxedaifgdrq8wx9h4kfzcouo6w8qcse X-Rspamd-Queue-Id: 60457100006 Authentication-Results: imf05.hostedemail.com; dkim=none; spf=pass (imf05.hostedemail.com: domain of "SRS0=+b1z=3X=xs4all.nl=hverkuil@kernel.org" designates 145.40.68.75 as permitted sender) smtp.mailfrom="SRS0=+b1z=3X=xs4all.nl=hverkuil@kernel.org"; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=xs4all.nl (policy=none) X-Rspamd-Server: rspam07 X-HE-Tag: 1669209982-498475 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: Hi David, Tomasz, On 16/11/2022 11:26, David Hildenbrand wrote: > FOLL_FORCE is really only for ptrace access. According to commit > 707947247e95 ("media: videobuf2-vmalloc: get_userptr: buffers are always > writable"), get_vaddr_frames() currently pins all pages writable as a > workaround for issues with read-only buffers. I've decided to revert 707947247e95: I have not been able to reproduce the problem described in that commit, and Tomasz reported that it caused problems with a specific use-case they encountered. I'll post that patch soon and I expect it to land in 6.2. It will cause a conflict with this patch, though. If the problem described in that patch occurs again, then I will revisit it and hopefully do a better job than I did before. That commit was not my finest moment. Regards, Hans > > FOLL_FORCE, however, seems to be a legacy leftover as it predates > commit 707947247e95 ("media: videobuf2-vmalloc: get_userptr: buffers are > always writable"). Let's just remove it. > > Once the read-only buffer issue has been resolved, FOLL_WRITE could > again be set depending on the DMA direction. > > Cc: Hans Verkuil > Cc: Marek Szyprowski > Cc: Tomasz Figa > Cc: Marek Szyprowski > Cc: Mauro Carvalho Chehab > Signed-off-by: David Hildenbrand > --- > drivers/media/common/videobuf2/frame_vector.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c > index 542dde9d2609..062e98148c53 100644 > --- a/drivers/media/common/videobuf2/frame_vector.c > +++ b/drivers/media/common/videobuf2/frame_vector.c > @@ -50,7 +50,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, > start = untagged_addr(start); > > ret = pin_user_pages_fast(start, nr_frames, > - FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM, > + FOLL_WRITE | FOLL_LONGTERM, > (struct page **)(vec->ptrs)); > if (ret > 0) { > vec->got_ref = true;