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 9583BECAAA1 for ; Wed, 7 Sep 2022 00:58:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1C6468D0002; Tue, 6 Sep 2022 20:58:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1766D6B0074; Tue, 6 Sep 2022 20:58:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 015F58D0002; Tue, 6 Sep 2022 20:58:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id E66086B0073 for ; Tue, 6 Sep 2022 20:58:30 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id B8C3480760 for ; Wed, 7 Sep 2022 00:58:30 +0000 (UTC) X-FDA: 79883478780.19.2127438 Received: from mail-yb1-f181.google.com (mail-yb1-f181.google.com [209.85.219.181]) by imf25.hostedemail.com (Postfix) with ESMTP id 7A1D7A0095 for ; Wed, 7 Sep 2022 00:58:30 +0000 (UTC) Received: by mail-yb1-f181.google.com with SMTP id c9so19342996ybf.5 for ; Tue, 06 Sep 2022 17:58:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=UjaiWINnbTXgT+URtVXx1fGemLW7KAjAuDjBEcKQcpw=; b=EAkdAoJF93b/9wVcZWS/8Z33Wh8Eq7xG8wCxKPHNm0Lldc4C5bChxoQDfIHIPRDYax E+7oO+L2O6scu7V+5fNLALkC2gSW3KtuP3tfNpYEXGlOWDD2sTiTX6OWgeeJAcpYfcqc A7KFsvQIqZJC3pSoupGeVX3b2h2lXfNqXDDwmhewWl9SZYpSIQb+K3ijuHEHBKnlI5iN 5YTs4xJNgeAVeEvcjs3kD0qLdfQNKm1QP8zoW0R448XpFNwDG9J12DbqDl3vZ1zKXm72 +HSPLoCsmPAhUhpPj99b2yJIbwOsGllYC7rvCmcvKG+KcIcU1HoAeaosy/7TBlwl5auu e43Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=UjaiWINnbTXgT+URtVXx1fGemLW7KAjAuDjBEcKQcpw=; b=CGGCWSvpZGX0ddXCKLuIuC1jPyEt9hSP5my8EWoidkTw8Kopvz2tmMbK5o2Tm05W94 4CMoTQUEWvXrxh988hLJEc4hHvwl1rTEVQNo0wVA1I96VOuIKWZ5CCkNn2Ue6na/mIVO YePmfX8YDhdyEc5oXPwOKX1UOCPq95ePQPZVJxXCfnjRXgUoxT52SCjo2Qbp5YmVCMuT tOehLKHWBkk04Qf1iglLom6TOwgl2heRelvK/dbBznmUaLQ0ZinY7m0N8qCHzLJi8rmb 6XhO8y4CBHAw+S4ra1t5NmhyCMpXbjOUPTJoJ8mfcYFeqvGDDMBY1nAMmImC0I+yr7ku 2FbA== X-Gm-Message-State: ACgBeo3Xt/Yk7HRL/Ydhik+t4Jc8bQorRouG77d0zx5nHGkhSsfjmu4F UIg8SjK9qjYrwPavxV/Nb7BuYy7KlSZFQof9ohPBBg== X-Google-Smtp-Source: AA6agR7/aESfD9/NDPsDFtQ7YKYMRNuKLSwT1FUjw+G1bf9VJ00olfdLIYvwBbmvvuSYroc7vvTiDT6ZBY0OsHmp1Qc= X-Received: by 2002:a25:9781:0:b0:6a9:561a:c143 with SMTP id i1-20020a259781000000b006a9561ac143mr995480ybo.59.1662512309570; Tue, 06 Sep 2022 17:58:29 -0700 (PDT) MIME-Version: 1.0 References: <20220901173516.702122-1-surenb@google.com> <20220901173516.702122-20-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Tue, 6 Sep 2022 17:58:18 -0700 Message-ID: Subject: Re: [RFC PATCH RESEND 19/28] mm: disallow do_swap_page to handle page faults under VMA lock To: Peter Xu Cc: Andrew Morton , Michel Lespinasse , Jerome Glisse , Michal Hocko , Vlastimil Babka , Johannes Weiner , Mel Gorman , Davidlohr Bueso , Matthew Wilcox , "Liam R. Howlett" , Peter Zijlstra , Laurent Dufour , Laurent Dufour , "Paul E . McKenney" , Andy Lutomirski , Song Liu , David Hildenbrand , dhowells@redhat.com, Hugh Dickins , Sebastian Andrzej Siewior , Kent Overstreet , David Rientjes , Axel Rasmussen , Joel Fernandes , Minchan Kim , kernel-team , linux-mm , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, LKML Content-Type: text/plain; charset="UTF-8" ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662512310; a=rsa-sha256; cv=none; b=g2m0Vfb3qklp6uctKiDC13Werwy6EIf3V3pfT2lcMD1EkaaoFGsFGKBSYCRERhW6EifFbG /5PbdGTJfJfRc7HwydvkEhztWV9ViCyztIP0QqyERs957/vwP3wVjnKnQwnyb1L4qqsOX4 A82e56W90tMeQ389JzoPEIi7xmWZHRQ= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=EAkdAoJF; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf25.hostedemail.com: domain of surenb@google.com designates 209.85.219.181 as permitted sender) smtp.mailfrom=surenb@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662512310; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UjaiWINnbTXgT+URtVXx1fGemLW7KAjAuDjBEcKQcpw=; b=pV+wGu8u+MmIoHsKP86mWe9uRi3XKdBWNxPA1S77LjUafompKosYm9QZRhiYTRHQZVc1Ov 08SPF5U6sljhlvGAABVX5y5wbtr5adXBa2S7H9NzKwDADwdeH4rAjABCQ8+d8bdbvOqzeD p2nJZPADlsChCBEDVKwtW/LdcG141d8= X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: syxdqakuemzfidniboh7s33k9qj5pma6 Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=EAkdAoJF; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf25.hostedemail.com: domain of surenb@google.com designates 209.85.219.181 as permitted sender) smtp.mailfrom=surenb@google.com X-Rspamd-Queue-Id: 7A1D7A0095 X-HE-Tag: 1662512310-59942 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 Tue, Sep 6, 2022 at 1:22 PM Peter Xu wrote: > > On Tue, Sep 06, 2022 at 01:08:10PM -0700, Suren Baghdasaryan wrote: > > On Tue, Sep 6, 2022 at 12:39 PM Peter Xu wrote: > > > > > > On Thu, Sep 01, 2022 at 10:35:07AM -0700, Suren Baghdasaryan wrote: > > > > Due to the possibility of do_swap_page dropping mmap_lock, abort fault > > > > handling under VMA lock and retry holding mmap_lock. This can be handled > > > > more gracefully in the future. > > > > > > > > Signed-off-by: Suren Baghdasaryan > > > > --- > > > > mm/memory.c | 5 +++++ > > > > 1 file changed, 5 insertions(+) > > > > > > > > diff --git a/mm/memory.c b/mm/memory.c > > > > index 9ac9944e8c62..29d2f49f922a 100644 > > > > --- a/mm/memory.c > > > > +++ b/mm/memory.c > > > > @@ -3738,6 +3738,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > > > > vm_fault_t ret = 0; > > > > void *shadow = NULL; > > > > > > > > + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { > > > > + ret = VM_FAULT_RETRY; > > > > + goto out; > > > > + } > > > > + > > > > > > May want to fail early similarly for handle_userfault() too for similar > > > reason. Thanks, > > > > I wasn't aware of a similar issue there. Will have a closer look. Thanks! > > Sure. > > Just in case this would be anything helpful - handle_userfault() will both > assert at the entry (mmap_assert_locked) and will in most cases release > read lock along the way when waiting for page fault resolutions. > > And userfaultfd should work on anonymous memory for either missing mode or > write protect mode. Got it. Thanks for the explanation. It definitely helps! > > Thanks, > > -- > Peter Xu > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >