From patchwork Thu Apr 28 08:34:26 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12830213 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 B9431C433EF for ; Thu, 28 Apr 2022 08:35:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 499C56B0073; Thu, 28 Apr 2022 04:35:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 44A046B0075; Thu, 28 Apr 2022 04:35:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2EB0B6B0078; Thu, 28 Apr 2022 04:35:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.28]) by kanga.kvack.org (Postfix) with ESMTP id 1E1FC6B0073 for ; Thu, 28 Apr 2022 04:35:07 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 06BD629722 for ; Thu, 28 Apr 2022 08:35:06 +0000 (UTC) X-FDA: 79405627812.03.EF2CB27 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf22.hostedemail.com (Postfix) with ESMTP id 8D5FBC0048 for ; Thu, 28 Apr 2022 08:35:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651134903; 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=uKusX70JiuPlYzcamhxyk77YgVkoB/zECZIBimqek94=; b=I5bBZaqhhWdIzsjtphCrBjx/s7AHir8ytbp6jhJOnkmO2SkeiCQ96sMCF+wY66xDyeh3nL 6U7DkVXJD6SLcIDLBgiQLjMTHAnA7FuCZa23cYlCWcAxU0SmdRmun+JJB8IvH2eX/cD34j Z/oeK/HpZ0WI+eH4J2ZOsQ+7VW+WC+g= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-647-fh7WDyYiMb-DxCtuxaHKhw-1; Thu, 28 Apr 2022 04:34:59 -0400 X-MC-Unique: fh7WDyYiMb-DxCtuxaHKhw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 639C3801005; Thu, 28 Apr 2022 08:34:58 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.194.113]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2576D55BA85; Thu, 28 Apr 2022 08:34:53 +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 v4 02/17] mm/hugetlb: take src_mm->write_protect_seq in copy_hugetlb_page_range() Date: Thu, 28 Apr 2022 10:34:26 +0200 Message-Id: <20220428083441.37290-3-david@redhat.com> In-Reply-To: <20220428083441.37290-1-david@redhat.com> References: <20220428083441.37290-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 X-Rspamd-Queue-Id: 8D5FBC0048 X-Stat-Signature: zmwn4rajgjt1gymhhf37a1ynsku3scq7 X-Rspam-User: Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=I5bBZaqh; spf=none (imf22.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam09 X-HE-Tag: 1651134905-823187 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: Let's do it just like copy_page_range(), taking the seqlock and making sure the mmap_lock is held in write mode. This allows for add a VM_BUG_ON to page_needs_cow_for_dma() and properly synchronizes concurrent fork() with GUP-fast of hugetlb pages, which will be relevant for further changes. Acked-by: Vlastimil Babka Signed-off-by: David Hildenbrand --- include/linux/mm.h | 4 ++++ mm/hugetlb.c | 8 ++++++-- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 9f44254af8ce..c3c862a2e533 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1576,6 +1576,8 @@ static inline bool page_maybe_dma_pinned(struct page *page) /* * This should most likely only be called during fork() to see whether we * should break the cow immediately for a page on the src mm. + * + * The caller has to hold the PT lock and the vma->vm_mm->->write_protect_seq. */ static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma, struct page *page) @@ -1583,6 +1585,8 @@ static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma, if (!is_cow_mapping(vma->vm_flags)) return false; + VM_BUG_ON(!(raw_read_seqcount(&vma->vm_mm->write_protect_seq) & 1)); + if (!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags)) return false; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 3fc721789743..670117bbc9b4 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4717,6 +4717,8 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, vma->vm_start, vma->vm_end); mmu_notifier_invalidate_range_start(&range); + mmap_assert_write_locked(src); + raw_write_seqcount_begin(&src->write_protect_seq); } else { /* * For shared mappings i_mmap_rwsem must be held to call @@ -4849,10 +4851,12 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, spin_unlock(dst_ptl); } - if (cow) + if (cow) { + raw_write_seqcount_end(&src->write_protect_seq); mmu_notifier_invalidate_range_end(&range); - else + } else { i_mmap_unlock_read(mapping); + } return ret; }