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=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 E03FCECDE20 for ; Wed, 11 Sep 2019 09:46:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C01222089F for ; Wed, 11 Sep 2019 09:46:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727538AbfIKJqL (ORCPT ); Wed, 11 Sep 2019 05:46:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36926 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726928AbfIKJqK (ORCPT ); Wed, 11 Sep 2019 05:46:10 -0400 Received: from mail-pl1-f197.google.com (mail-pl1-f197.google.com [209.85.214.197]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 88E1A11A2D for ; Wed, 11 Sep 2019 09:46:09 +0000 (UTC) Received: by mail-pl1-f197.google.com with SMTP id h17so10166512plr.11 for ; Wed, 11 Sep 2019 02:46:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=aGQLRgm7G2kTyYY3bxXh1HW8rTy0El4wjuzgSvgBfMw=; b=Wm/mEgy0gbz8IuXFB/PhxosffIiV0XCfJQ3S8HxOCyIcMHUujIrc6bbJQ09fgshs8k 1/N+Vb/Bz9QnARL/+qxBJJGn81VuLYqsTDLIVPWebpw2SaEROxkGyztYR58WCqrv/Mhy /Gll2/IYTQPN2950q9nb0pRgPmgsBtg41lygzdyA8OZ2sRW81Rknp8URXG1DJbB+3Vpb V7yVGO/NWjVWvwTW6oPg71F20049jiB+ifWeRyZAn2WQGUHWn/vQhqgeWMNQC2PQfEM7 zaZqxZES6orZWJ7cgJiUAItwviwY7isZvhqy9y9zeTYKhB14NeHxMvERwWIXleTo7zbc u3yA== X-Gm-Message-State: APjAAAUqotuc37ZqXCKfYBdxA4K5iEOApLpJWZRAFID/dsanuwZXpb/c DJzbiFArU5Hylbsx3dMcu7IpUaIwy55NscPDGsFWu+JZbY8LnDVEramXYkkg86lT9xviHMjRewE URTmmh6MHHVABw3c5RU/IABcA X-Received: by 2002:a17:90b:8d7:: with SMTP id ds23mr4268270pjb.141.1568195169013; Wed, 11 Sep 2019 02:46:09 -0700 (PDT) X-Google-Smtp-Source: APXvYqyLp2sZfcawkJJYszjOJIQ4z7kr7IN7Q37DCMo9yfe4m+hzrzukPqOTG4qN8IJMbHZpOAm2IA== X-Received: by 2002:a17:90b:8d7:: with SMTP id ds23mr4268232pjb.141.1568195168646; Wed, 11 Sep 2019 02:46:08 -0700 (PDT) Received: from xz-x1.redhat.com ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id j7sm21610436pfi.96.2019.09.11.02.46.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Sep 2019 02:46:07 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Peter Xu , David Hildenbrand , Hugh Dickins , Maya Gokhale , Jerome Glisse , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Marty McFadden , Shaohua Li , Andrea Arcangeli , Mike Kravetz , Denis Plotnikov , Mike Rapoport , Linus Torvalds , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" Subject: [PATCH v3.1 7/7] mm/gup: Allow VM_FAULT_RETRY for multiple times Date: Wed, 11 Sep 2019 17:45:55 +0800 Message-Id: <20190911094555.9180-1-peterx@redhat.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190911071007.20077-8-peterx@redhat.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is the gup counterpart of the change that allows the VM_FAULT_RETRY to happen for more than once. One thing to mention is that we must check the fatal signal here before retry because the GUP can be interrupted by that, otherwise we can loop forever. Signed-off-by: Peter Xu --- mm/gup.c | 25 ++++++++++++++++++++----- mm/hugetlb.c | 6 ++++-- 2 files changed, 24 insertions(+), 7 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index eddbb95dcb8f..4b9413ee7b23 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -644,7 +644,10 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma, if (*flags & FOLL_NOWAIT) fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; if (*flags & FOLL_TRIED) { - VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY); + /* + * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED + * can co-exist + */ fault_flags |= FAULT_FLAG_TRIED; } @@ -1059,17 +1062,29 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk, if (likely(pages)) pages += ret; start += ret << PAGE_SHIFT; + lock_dropped = true; +retry: /* * Repeat on the address that fired VM_FAULT_RETRY - * without FAULT_FLAG_ALLOW_RETRY but with - * FAULT_FLAG_TRIED. + * with both FAULT_FLAG_ALLOW_RETRY and + * FAULT_FLAG_TRIED. Note that GUP can be interrupted + * by fatal signals, so we need to check it before we + * start trying again otherwise it can loop forever. */ + + if (fatal_signal_pending(current)) + break; + *locked = 1; - lock_dropped = true; down_read(&mm->mmap_sem); ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED, - pages, NULL, NULL); + pages, NULL, locked); + if (!*locked) { + /* Continue to retry until we succeeded */ + BUG_ON(ret != 0); + goto retry; + } if (ret != 1) { BUG_ON(ret > 1); if (!pages_done) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 31c2a6275023..d0c98cff5b0f 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4347,8 +4347,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; if (flags & FOLL_TRIED) { - VM_WARN_ON_ONCE(fault_flags & - FAULT_FLAG_ALLOW_RETRY); + /* + * Note: FAULT_FLAG_ALLOW_RETRY and + * FAULT_FLAG_TRIED can co-exist + */ fault_flags |= FAULT_FLAG_TRIED; } ret = hugetlb_fault(mm, vma, vaddr, fault_flags); -- 2.21.0