Messages in this thread | | | Date | Thu, 2 Apr 2015 18:05:10 -0700 (PDT) | From | Hugh Dickins <> | Subject | Re: [patch -mm] mm, doc: cleanup and clarify munmap behavior for hugetlb memory fix |
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On Thu, 2 Apr 2015, David Rientjes wrote:
> 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>
Thanks, yes, good wording: it is best to be a bit vague here, since each msyscall takes the approach most convenient for it.
Acked-by: Hugh Dickins <hughd@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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