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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5BC22C433EF for ; Thu, 24 Feb 2022 12:28:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234357AbiBXM2b (ORCPT ); Thu, 24 Feb 2022 07:28:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39836 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231905AbiBXM23 (ORCPT ); Thu, 24 Feb 2022 07:28:29 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 22A70175860 for ; Thu, 24 Feb 2022 04:27:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1645705678; 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=RXAvt29aks092V89TFuSrIQhc1KpFNVRX0HPI0UZk40=; b=L7ZOEFCGhNmnwstDHcZSuV/62aOUVpzvyqT5iYfzbhGFvJ2SxehwiWClxiZUlEHtfwIfcI UBT0BHAUwJyLSctQmYjiKYdf9YbOVQpsh94VOH2rqC/BZZqJjkdVXQXj1fOI83qaVN1m7v LGFOG1CwH01pvg7QZVEJ2So6kwNheq8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-577-PCUaTtRzMeag2gOqQMBV7w-1; Thu, 24 Feb 2022 07:27:55 -0500 X-MC-Unique: PCUaTtRzMeag2gOqQMBV7w-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E12221006AA6; Thu, 24 Feb 2022 12:27:51 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.194.160]) by smtp.corp.redhat.com (Postfix) with ESMTP id CF4552634C; Thu, 24 Feb 2022 12:27:28 +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 RFC 02/13] mm/hugetlb: take src_mm->write_protect_seq in copy_hugetlb_page_range() Date: Thu, 24 Feb 2022 13:26:03 +0100 Message-Id: <20220224122614.94921-3-david@redhat.com> In-Reply-To: <20220224122614.94921-1-david@redhat.com> References: <20220224122614.94921-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 cocnurrent fork() with GUP-fast of hugetlb pages, which will be relevant for further changes. 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 a12291cfe5dd..b29cb8bacd59 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1323,6 +1323,8 @@ static inline bool is_cow_mapping(vm_flags_t flags) /* * 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) @@ -1330,6 +1332,8 @@ 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 61895cc01d09..e2e2d0f3f259 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4710,6 +4710,8 @@ 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 @@ -4842,10 +4844,12 @@ 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; } -- 2.35.1