From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f181.google.com (mail-wi0-f181.google.com [209.85.212.181]) by kanga.kvack.org (Postfix) with ESMTP id 44CD56B0279 for ; Wed, 22 Jul 2015 13:17:03 -0400 (EDT) Received: by wicgb10 with SMTP id gb10so107760519wic.1 for ; Wed, 22 Jul 2015 10:17:02 -0700 (PDT) Received: from mail-wi0-x22f.google.com (mail-wi0-x22f.google.com. [2a00:1450:400c:c05::22f]) by mx.google.com with ESMTPS id gp7si3554072wjc.131.2015.07.22.10.17.01 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Jul 2015 10:17:01 -0700 (PDT) Received: by wibxm9 with SMTP id xm9so172973743wib.0 for ; Wed, 22 Jul 2015 10:17:01 -0700 (PDT) Message-ID: <55AFD009.6080706@gmail.com> Date: Wed, 22 Jul 2015 19:16:57 +0200 From: "Michael Kerrisk (man-pages)" MIME-Version: 1.0 Subject: Re: [patch] mmap.2: document the munmap exception for underlying page size References: In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: mtk.manpages@gmail.com, Hugh Dickins , Davide Libenzi , Eric B Munson , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-man@vger.kernel.org Hi David, On 07/22/2015 02:41 AM, David Rientjes wrote: > munmap(2) will fail with an errno of EINVAL for hugetlb memory if the > length is not a multiple of the underlying page size. > > Documentation/vm/hugetlbpage.txt was updated to specify this behavior > since Linux 4.1 in commit 80d6b94bd69a ("mm, doc: cleanup and clarify > munmap behavior for hugetlb memory"). > > Signed-off-by: David Rientjes > --- > man2/mmap.2 | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/man2/mmap.2 b/man2/mmap.2 > --- a/man2/mmap.2 > +++ b/man2/mmap.2 > @@ -383,6 +383,10 @@ All pages containing a part > of the indicated range are unmapped, and subsequent references > to these pages will generate > .BR SIGSEGV . > +An exception is when the underlying memory is not of the native page > +size, such as hugetlb page sizes, whereas > +.I length > +must be a multiple of the underlying page size. > It is not an error if the > indicated range does not contain any mapped pages. > .SS Timestamps changes for file-backed mappings I'm struggling a bit to understand your text. Is the point this: If we have a hugetlb area, then the munmap() length must be a multiple of the page size. ? Are there any requirements about 'addr'? Must it also me huge-page-aligned? Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org