From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) by kanga.kvack.org (Postfix) with ESMTP id 7C6598E009D for ; Tue, 8 Jan 2019 21:02:10 -0500 (EST) Received: by mail-qt1-f198.google.com with SMTP id j5so5221110qtk.11 for ; Tue, 08 Jan 2019 18:02:10 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id j14si753700qvm.164.2019.01.08.18.02.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Jan 2019 18:02:09 -0800 (PST) From: Andrea Arcangeli Subject: [PATCH 1/1] mm/hugetlb.c: teach follow_hugetlb_page() to handle FOLL_NOWAIT Date: Tue, 8 Jan 2019 21:02:03 -0500 Message-Id: <20190109020203.26669-2-aarcange@redhat.com> In-Reply-To: <20190109020203.26669-1-aarcange@redhat.com> References: <20190109020203.26669-1-aarcange@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mike Rapoport , Mike Kravetz , Peter Xu , "Dr. David Alan Gilbert" hugetlb needs the same fix as faultin_nopage (which was applied in 96312e61282ae3f6537a562625706498cbc75594) or KVM hangs because it thinks the mmap_sem was already released by hugetlb_fault() if it returned VM_FAULT_RETRY, but it wasn't in the FOLL_NOWAIT case. Fixes: ce53053ce378 ("kvm: switch get_user_page_nowait() to get_user_pages_unlocked()") Signed-off-by: Andrea Arcangeli Tested-by: "Dr. David Alan Gilbert" Reported-by: "Dr. David Alan Gilbert" --- mm/hugetlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index e37efd5d8318..b3622d7888c8 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4301,7 +4301,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, break; } if (ret & VM_FAULT_RETRY) { - if (nonblocking) + if (nonblocking && + !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) *nonblocking = 0; *nr_pages = 0; /*