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 X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 5D074ECE560 for ; Mon, 17 Sep 2018 13:38:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 150532147A for ; Mon, 17 Sep 2018 13:38:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 150532147A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728412AbeIQTFw (ORCPT ); Mon, 17 Sep 2018 15:05:52 -0400 Received: from mga09.intel.com ([134.134.136.24]:47172 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726865AbeIQTFv (ORCPT ); Mon, 17 Sep 2018 15:05:51 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Sep 2018 06:38:28 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,385,1531810800"; d="scan'208";a="90780111" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga001.fm.intel.com with ESMTP; 17 Sep 2018 06:38:25 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id D827713F; Mon, 17 Sep 2018 16:38:24 +0300 (EEST) From: "Kirill A. Shutemov" To: Andrew Morton Cc: Vegard Nossum , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , stable@vger.kernel.org, Zi Yan , Naoya Horiguchi , Vlastimil Babka , Andrea Arcangeli Subject: [PATCHv2] mm, thp: Fix mlocking THP page with migration enabled Date: Mon, 17 Sep 2018 16:38:16 +0300 Message-Id: <20180917133816.43995-1-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.18.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A transparent huge page is represented by a single entry on an LRU list. Therefore, we can only make unevictable an entire compound page, not individual subpages. If a user tries to mlock() part of a huge page, we want the rest of the page to be reclaimable. We handle this by keeping PTE-mapped huge pages on normal LRU lists: the PMD on border of VM_LOCKED VMA will be split into PTE table. Introduction of THP migration breaks[1] the rules around mlocking THP pages. If we had a single PMD mapping of the page in mlocked VMA, the page will get mlocked, regardless of PTE mappings of the page. For tmpfs/shmem it's easy to fix by checking PageDoubleMap() in remove_migration_pmd(). Anon THP pages can only be shared between processes via fork(). Mlocked page can only be shared if parent mlocked it before forking, otherwise CoW will be triggered on mlock(). For Anon-THP, we can fix the issue by munlocking the page on removing PTE migration entry for the page. PTEs for the page will always come after mlocked PMD: rmap walks VMAs from oldest to newest. Test-case: #include #include #include #include #include int main(void) { unsigned long nodemask = 4; void *addr; addr = mmap((void *)0x20000000UL, 2UL << 20, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_LOCKED, -1, 0); if (fork()) { wait(NULL); return 0; } mlock(addr, 4UL << 10); mbind(addr, 2UL << 20, MPOL_PREFERRED | MPOL_F_RELATIVE_NODES, &nodemask, 4, MPOL_MF_MOVE); return 0; } [1] https://lkml.kernel.org/r/CAOMGZ=G52R-30rZvhGxEbkTw7rLLwBGadVYeo--iizcD3upL3A@mail.gmail.com Signed-off-by: Kirill A. Shutemov Reported-by: Vegard Nossum Fixes: 616b8371539a ("mm: thp: enable thp migration in generic path") Cc: [v4.14+] Cc: Zi Yan Cc: Naoya Horiguchi Cc: Vlastimil Babka Cc: Andrea Arcangeli --- mm/huge_memory.c | 2 +- mm/migrate.c | 3 +++ 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 533f9b00147d..00704060b7f7 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2931,7 +2931,7 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) else page_add_file_rmap(new, true); set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); - if (vma->vm_flags & VM_LOCKED) + if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new)) mlock_vma_page(new); update_mmu_cache_pmd(vma, address, pvmw->pmd); } diff --git a/mm/migrate.c b/mm/migrate.c index d6a2e89b086a..9d374011c244 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -275,6 +275,9 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma, if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new)) mlock_vma_page(new); + if (PageTransHuge(page) && PageMlocked(page)) + clear_page_mlock(page); + /* No need to invalidate - it was non-present before */ update_mmu_cache(vma, pvmw.address, pvmw.pte); } -- 2.18.0