linux-kernel - [PATCH] mm/mremap: Document MREMAP_FIXED dependency on MREMAP

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Message-Id: <20170710113211.31394-1-khandual@linux.vnet.ibm.com>
Date:   Mon, 10 Jul 2017 17:02:11 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     akpm@...ux-foundation.org, mike.kravetz@...cle.com
Subject: [PATCH] mm/mremap: Document MREMAP_FIXED dependency on MREMAP_MAYMOVE

In the header file, just specify the dependency of MREMAP_FIXED
on MREMAP_MAYMOVE and make it explicit for the user space.

Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
---
 include/uapi/linux/mman.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
index ade4acd..8cae3f6 100644
--- a/include/uapi/linux/mman.h
+++ b/include/uapi/linux/mman.h
@@ -3,8 +3,10 @@
 
 #include <asm/mman.h>
 
-#define MREMAP_MAYMOVE	1
-#define MREMAP_FIXED	2
+#define MREMAP_MAYMOVE	1 /* VMA can move after remap and resize */
+#define MREMAP_FIXED	2 /* VMA can remap at particular address */
+
+/* NOTE: MREMAP_FIXED must be set with MREMAP_MAYMOVE, not alone */
 
 #define OVERCOMMIT_GUESS		0
 #define OVERCOMMIT_ALWAYS		1
-- 
1.8.5.2