From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hugh Dickins Subject: Re: [patch -mm] mm, doc: cleanup and clarify munmap behavior for hugetlb memory fix Date: Thu, 2 Apr 2015 18:05:10 -0700 (PDT) Message-ID: References: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: Sender: owner-linux-mm@kvack.org To: David Rientjes Cc: Andrew Morton , Hugh Dickins , Jonathan Corbet , Davide Libenzi , Luiz Capitulino , Shuah Khan , Andrea Arcangeli , Joern Engel , Jianguo Wu , Eric B Munson , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org List-Id: linux-api@vger.kernel.org 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 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 > --- > 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org