mm, doc: cleanup and clarify munmap behavior for hugetlb memory fix

Don't only specify munmap(2) behavior with respect the hugetlb memory, all
other syscalls get naturally aligned to the native page size of the
processor.  Rather, pick out munmap(2) as a specific example.

Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt
index 1270fb1ee7150b2c12da4b2a421b9f89f4565923..030977fb8d2dcb0cb820b5989b9c0cfedd3c2d83 100644 (file)
--- a/Documentation/vm/hugetlbpage.txt
+++ b/Documentation/vm/hugetlbpage.txt
@@ -313,8 +313,11 @@ into /proc/sys/vm/hugetlb_shm_group.  It is possible for same or different
 applications to use any combination of mmaps and shm* calls, though the mount of
 filesystem will be required for using mmap calls without MAP_HUGETLB.
 
-When using munmap(2) to unmap hugetlb memory, the length specified must be
-hugepage aligned, otherwise it will fail with errno set to EINVAL.
+Syscalls that operate on memory backed by hugetlb pages only have their lengths
+aligned to the native page size of the processor; they will normally fail with
+errno set to EINVAL or exclude hugetlb pages that extend beyond the length if
+not hugepage aligned.  For example, munmap(2) will fail if memory is backed by
+a hugetlb page and the length is smaller than the hugepage size.
 
 
 Examples