Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753302AbbGVXbn (ORCPT ); Wed, 22 Jul 2015 19:31:43 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:49384 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751154AbbGVXbm (ORCPT ); Wed, 22 Jul 2015 19:31:42 -0400 Message-ID: <55B027D3.4020608@oracle.com> Date: Wed, 22 Jul 2015 16:31:31 -0700 From: Mike Kravetz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: David Rientjes , mtk.manpages@gmail.com CC: Hugh Dickins , Davide Libenzi , Eric B Munson , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-man@vger.kernel.org Subject: Re: [patch] mmap.2: document the munmap exception for underlying page size References: In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1674 Lines: 47 On 07/21/2015 05:41 PM, 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 > > -- Should we also add a similar comment for the mmap offset? Currently the man page says: "offset must be a multiple of the page size as returned by sysconf(_SC_PAGE_SIZE)." For hugetlbfs, I beieve the offset must be a multiple of the hugetlb page size. A similar comment/exception about using the "underlying page size" would apply here as well. -- Mike Kravetz -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/