Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751541AbdIOVoH (ORCPT ); Fri, 15 Sep 2017 17:44:07 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:34249 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750871AbdIOVoE (ORCPT ); Fri, 15 Sep 2017 17:44:04 -0400 From: Mike Kravetz To: mtk.manpages@gmail.com Cc: linux-man@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Michal Hocko , Hugh Dickins , Andrea Arcangeli , "Kirill A . Shutemov" , Mike Kravetz Subject: [patch] memfd_create.2: Add description of MFD_HUGETLB (hugetlbfs) support Date: Fri, 15 Sep 2017 14:43:05 -0700 Message-Id: <20170915214305.7148-1-mike.kravetz@oracle.com> X-Mailer: git-send-email 2.13.5 X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1901 Lines: 57 hugetlbfs support for memfd_create was recently merged by Linus and should be in the Linux 4.14 release. To request hugetlbfs support a new memfd_create flag (MFD_HUGETLB) was added. This patch documents the following commit: commit 749df87bd7bee5a79cef073f5d032ddb2b211de8 Author: Mike Kravetz Date: Wed Sep 6 16:24:16 2017 -0700 mm/shmem: add hugetlbfs support to memfd_create() Signed-off-by: Mike Kravetz --- man2/memfd_create.2 | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/man2/memfd_create.2 b/man2/memfd_create.2 index 4dfd1bb2d..b61254bb8 100644 --- a/man2/memfd_create.2 +++ b/man2/memfd_create.2 @@ -100,6 +100,33 @@ If this flag is not set, the initial set of seals will be meaning that no other seals can be set on the file. .\" FIXME Why is the MFD_ALLOW_SEALING behavior not simply the default? .\" Is it worth adding some text explaining this? +.TP +.BR MFD_HUGETLB " (since Linux 4.14)" +The anonymous file will be created in the hugetlbfs filesystem using +huge pages. See the Linux kernel source file +.I Documentation/vm/hugetlbpage.txt +for more information about hugetlbfs. The hugetlbfs filesystem does +not support file sealing operations. Therefore, specifying both +.B MFD_HUGETLB +and +.B MFD_ALLOW_SEALING +will result in an error +.RB (EINVAL) +being returned. + +.TP +.BR MFD_HUGE_2MB ", " MFD_HUGE_1GB ", " "..." +Used in conjunction with +.B MFD_HUGETLB +to select alternative hugetlb page sizes (respectively, 2 MB, 1 GB, ...) +on systems that support multiple hugetlb page sizes. Definitions for known +huge page sizes are included in the header file +.I . + +For details on encoding huge page sizes not included in the header file, +see the discussion of the similarly named constants in +.BR mmap (2). + .PP Unused bits in .I flags -- 2.13.5