[patch -mm] mm, doc: cleanup and clarify munmap behavior for hugetlb memory fix
From: David Rientjes <rientjes@google.com>
Date: 2015-04-02 22:50:22
Also in:
linux-mm, lkml
Subsystem:
documentation, the rest · Maintainers:
Jonathan Corbet, Linus Torvalds
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> --- Documentation/vm/hugetlbpage.txt | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt
index 1270fb1..030977f 100644
--- 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 --
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