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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 C6ECCC433DF for ; Fri, 16 Oct 2020 03:12:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F4AC20B1F for ; Fri, 16 Oct 2020 03:12:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602817979; bh=6modujK1KqEcnF77PHRhJ1t0xgjkAj5BhbMCyPdrZu8=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=PTAf+NioKh3+LW5E4POQ8lTBG0WiN5gpOVF2+yt9VoldZBVd9s6lfRWBH8RUpjclm 6hBToPOc3M9TlYetW+zbM4HNzsbEBpgxIeOpQN9d33f7ptaEjaebq18YvtneKED+4x qm/i5BOEu7LGV762ZJHqme6AHYGX1JWE+KScyaqo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392953AbgJPDM7 (ORCPT ); Thu, 15 Oct 2020 23:12:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:48816 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389908AbgJPDM6 (ORCPT ); Thu, 15 Oct 2020 23:12:58 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 19CD1208E4; Fri, 16 Oct 2020 03:12:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602817978; bh=6modujK1KqEcnF77PHRhJ1t0xgjkAj5BhbMCyPdrZu8=; h=Date:From:To:Subject:In-Reply-To:From; b=WMDcetgzEeSd8kcQkCBgzltOscAhe6ICuji1Kwwb16Ysx9fLQE03phMXQE0LULfdX iT5HUGbCFWX1GmukuTN4InbMiNLo1cSzOa3+9i0a6iDuKpohH1swr0nQJ0HrCpIhVo x8E1LyWy5T6pNiz+wBm4Y0px9XY0przsA7nKZYgk= Date: Thu, 15 Oct 2020 20:12:57 -0700 From: Andrew Morton To: akpm@linux-foundation.org, ebiederm@xmission.com, hch@lst.de, hughd@google.com, jannh@google.com, mm-commits@vger.kernel.org, oleg@redhat.com, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk Subject: [patch 141/156] mm/gup: take mmap_lock in get_dump_page() Message-ID: <20201016031257.VT__Apprg%akpm@linux-foundation.org> In-Reply-To: <20201015194043.84cda0c1d6ca2a6847f2384a@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Jann Horn Subject: mm/gup: take mmap_lock in get_dump_page() Properly take the mmap_lock before calling into the GUP code from get_dump_page(); and play nice, allowing the GUP code to drop the mmap_lock if it has to sleep. As Linus pointed out, we don't actually need the VMA because __get_user_pages() will flush the dcache for us if necessary. Link: http://lkml.kernel.org/r/20200827114932.3572699-7-jannh@google.com Signed-off-by: Jann Horn Acked-by: Linus Torvalds Cc: Christoph Hellwig Cc: Alexander Viro Cc: "Eric W . Biederman" Cc: Oleg Nesterov Cc: Hugh Dickins Signed-off-by: Andrew Morton --- mm/gup.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) --- a/mm/gup.c~mm-gup-take-mmap_lock-in-get_dump_page +++ a/mm/gup.c @@ -1547,19 +1547,23 @@ finish_or_fault: * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - * allowing a hole to be left in the corefile to save diskspace. * - * Called without mmap_lock, but after all other threads have been killed. + * Called without mmap_lock (takes and releases the mmap_lock by itself). */ #ifdef CONFIG_ELF_CORE struct page *get_dump_page(unsigned long addr) { - struct vm_area_struct *vma; + struct mm_struct *mm = current->mm; struct page *page; + int locked = 1; + int ret; - if (__get_user_pages_locked(current->mm, addr, 1, &page, &vma, NULL, - FOLL_FORCE | FOLL_DUMP | FOLL_GET) < 1) + if (mmap_read_lock_killable(mm)) return NULL; - flush_cache_page(vma, addr, page_to_pfn(page)); - return page; + ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked, + FOLL_FORCE | FOLL_DUMP | FOLL_GET); + if (locked) + mmap_read_unlock(mm); + return (ret == 1) ? page : NULL; } #endif /* CONFIG_ELF_CORE */ _