linux-kernel - [patch] mmap.2: document the munmap exception for underlying page size

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Date:	Tue, 21 Jul 2015 17:41:34 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	mtk.manpages@...il.com
cc:	Hugh Dickins <hughd@...gle.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Eric B Munson <emunson@...mai.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-man@...r.kernel.org
Subject: [patch] mmap.2: document the munmap exception for underlying page
 size

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 <rientjes@...gle.com>
---
 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
--
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