From patchwork Mon Jun 7 20:41:24 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 455734 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ECC33C4743F for ; Mon, 7 Jun 2021 20:41:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D31C361153 for ; Mon, 7 Jun 2021 20:41:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231534AbhFGUne (ORCPT ); Mon, 7 Jun 2021 16:43:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:58448 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230389AbhFGUnc (ORCPT ); Mon, 7 Jun 2021 16:43:32 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 96EC061159; Mon, 7 Jun 2021 20:41:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1623098484; bh=irW1ZGKbfJX4BpTrUbh80bcG42IL6BWcZQGZqJctGjI=; h=Date:From:To:Subject:From; b=MCEi12LoCQIfKfPSGblpgLVrK14Foc7XAtHIu1eK5ppOBWsXJ3Wb9Se4FRMVVp0TG BXEzZ+drNbK7Hl38GIAtLKsU+cOqCUGUbsTiuBdxFYJJ+pJsNs7a9kyDkytuHhVuvN I0CNx9USFe4vHTu2aWgQ93+eBcUxctOLC/Jx+oPw= Date: Mon, 07 Jun 2021 13:41:24 -0700 From: akpm@linux-foundation.org To: almasrymina@google.com, axelrasmussen@google.com, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, peterx@redhat.com, stable@vger.kernel.org Subject: [merged] mm-hugetlb-fix-simple-resv_huge_pages-underflow-on-uffdio_copy.patch removed from -mm tree Message-ID: <20210607204124.nq0OxGVyS%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm, hugetlb: fix simple resv_huge_pages underflow on UFFDIO_COPY has been removed from the -mm tree. Its filename was mm-hugetlb-fix-simple-resv_huge_pages-underflow-on-uffdio_copy.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Mina Almasry Subject: mm, hugetlb: fix simple resv_huge_pages underflow on UFFDIO_COPY The userfaultfd hugetlb tests cause a resv_huge_pages underflow. This happens when hugetlb_mcopy_atomic_pte() is called with !is_continue on an index for which we already have a page in the cache. When this happens, we allocate a second page, double consuming the reservation, and then fail to insert the page into the cache and return -EEXIST. To fix this, we first check if there is a page in the cache which already consumed the reservation, and return -EEXIST immediately if so. There is still a rare condition where we fail to copy the page contents AND race with a call for hugetlb_no_page() for this index and again we will underflow resv_huge_pages. That is fixed in a more complicated patch not targeted for -stable. Test: Hacked the code locally such that resv_huge_pages underflows produce a warning, then: ./tools/testing/selftests/vm/userfaultfd hugetlb_shared 10 2 /tmp/kokonut_test/huge/userfaultfd_test && echo test success ./tools/testing/selftests/vm/userfaultfd hugetlb 10 2 /tmp/kokonut_test/huge/userfaultfd_test && echo test success Both tests succeed and produce no warnings. After the test runs number of free/resv hugepages is correct. [mike.kravetz@oracle.com: changelog fixes] Link: https://lkml.kernel.org/r/20210528004649.85298-1-almasrymina@google.com Fixes: 8fb5debc5fcd ("userfaultfd: hugetlbfs: add hugetlb_mcopy_atomic_pte for userfaultfd support") Signed-off-by: Mina Almasry Reviewed-by: Mike Kravetz Cc: Axel Rasmussen Cc: Peter Xu Cc: Signed-off-by: Andrew Morton --- mm/hugetlb.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) --- a/mm/hugetlb.c~mm-hugetlb-fix-simple-resv_huge_pages-underflow-on-uffdio_copy +++ a/mm/hugetlb.c @@ -4889,10 +4889,20 @@ int hugetlb_mcopy_atomic_pte(struct mm_s if (!page) goto out; } else if (!*pagep) { - ret = -ENOMEM; + /* If a page already exists, then it's UFFDIO_COPY for + * a non-missing case. Return -EEXIST. + */ + if (vm_shared && + hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { + ret = -EEXIST; + goto out; + } + page = alloc_huge_page(dst_vma, dst_addr, 0); - if (IS_ERR(page)) + if (IS_ERR(page)) { + ret = -ENOMEM; goto out; + } ret = copy_huge_page_from_user(page, (const void __user *) src_addr,