From patchwork Tue Mar 29 16:04:37 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12795045 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 667B2C433F5 for ; Tue, 29 Mar 2022 16:06:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E65B98D0006; Tue, 29 Mar 2022 12:06:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E15308D0002; Tue, 29 Mar 2022 12:06:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C8F718D0006; Tue, 29 Mar 2022 12:06:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0153.hostedemail.com [216.40.44.153]) by kanga.kvack.org (Postfix) with ESMTP id BA1BA8D0002 for ; Tue, 29 Mar 2022 12:06:46 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 759F418296D2B for ; Tue, 29 Mar 2022 16:06:46 +0000 (UTC) X-FDA: 79297902012.23.969FE0A Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf11.hostedemail.com (Postfix) with ESMTP id D0D5D40014 for ; Tue, 29 Mar 2022 16:06:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1648570005; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=FIPqijxO2r9AEKGwPeBSz5qnlue4LDG+s4ZRW2g1hJE=; b=L0iRPQ34cDxJK0prOeiVJexo6aCxprfheAVPF2ia9LRaqa5vF5BoO1ESs490MqqDEC/nYa gUYn9b/1YLPaGSxeZKPJAHbP4Te1oCtfMAAIV8vGjAozYsxbVvU7P8CuGkWP4w4HlBUnt/ K9yR84db3roSKBpXIhHuZLprH7OjPio= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-362-H4fXtel1N5aPFdTQPTyb1A-1; Tue, 29 Mar 2022 12:06:42 -0400 X-MC-Unique: H4fXtel1N5aPFdTQPTyb1A-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9378E2805512; Tue, 29 Mar 2022 16:06:40 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.194.134]) by smtp.corp.redhat.com (Postfix) with ESMTP id E0F50401E26; Tue, 29 Mar 2022 16:06:33 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Hugh Dickins , Linus Torvalds , David Rientjes , Shakeel Butt , John Hubbard , Jason Gunthorpe , Mike Kravetz , Mike Rapoport , Yang Shi , "Kirill A . Shutemov" , Matthew Wilcox , Vlastimil Babka , Jann Horn , Michal Hocko , Nadav Amit , Rik van Riel , Roman Gushchin , Andrea Arcangeli , Peter Xu , Donald Dutile , Christoph Hellwig , Oleg Nesterov , Jan Kara , Liang Zhang , Pedro Gomes , Oded Gabbay , linux-mm@kvack.org, David Hildenbrand Subject: [PATCH v3 13/16] mm/gup: disallow follow_page(FOLL_PIN) Date: Tue, 29 Mar 2022 18:04:37 +0200 Message-Id: <20220329160440.193848-14-david@redhat.com> In-Reply-To: <20220329160440.193848-1-david@redhat.com> References: <20220329160440.193848-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: u8o1c8dm7mmkouim3hn7tksy1fmgrki5 Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=L0iRPQ34; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf11.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=david@redhat.com X-Rspamd-Queue-Id: D0D5D40014 X-HE-Tag: 1648570005-593447 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: We want to change the way we handle R/O pins on anonymous pages that might be shared: if we detect a possibly shared anonymous page -- mapped R/O and not !PageAnonExclusive() -- we want to trigger unsharing via a page fault, resulting in an exclusive anonymous page that can be pinned reliably without getting replaced via COW on the next write fault. However, the required page fault will be problematic for follow_page(): in contrast to ordinary GUP, follow_page() doesn't trigger faults internally. So we would have to end up failing a R/O pin via follow_page(), although there is something mapped R/O into the page table, which might be rather surprising. We don't seem to have follow_page(FOLL_PIN) users, and it's a purely internal MM function. Let's just make our life easier and the semantics of follow_page() clearer by just disallowing FOLL_PIN for follow_page() completely. Signed-off-by: David Hildenbrand Acked-by: Vlastimil Babka --- mm/gup.c | 3 +++ mm/hugetlb.c | 8 +++++--- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 271fbe8195d7..f96fc415ea6c 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -787,6 +787,9 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, if (vma_is_secretmem(vma)) return NULL; + if (foll_flags & FOLL_PIN) + return NULL; + page = follow_page_mask(vma, address, foll_flags, &ctx); if (ctx.pgmap) put_dev_pagemap(ctx.pgmap); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 6910545f028e..75b689ce21c5 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6698,9 +6698,11 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address, spinlock_t *ptl; pte_t pte; - /* FOLL_GET and FOLL_PIN are mutually exclusive. */ - if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == - (FOLL_PIN | FOLL_GET))) + /* + * FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via + * follow_hugetlb_page(). + */ + if (WARN_ON_ONCE(flags & FOLL_PIN)) return NULL; retry: