Re: HUGETLB commit handling.

[Andy Whitcroft <apw@shadowen.org>]

--On Thursday, April 08, 2004 15:47:42 -0700 Andrew Morton <akpm@osdl.org> wrote:

> Andy Whitcroft <apw@shadowen.org> wrote:
>>
>> We have been looking at the HUGETLB page commit issue (offlist) and are
>> close a final merged patch.
>
> Be aware that I've merged a patch from Bill which does all the hugetlb code
> unduplication.  A thousand lines gone:
>
>  25-akpm/arch/i386/mm/hugetlbpage.c    |  264 ----------------------------------
>  25-akpm/arch/ia64/mm/hugetlbpage.c    |  251 --------------------------------
>  25-akpm/arch/ppc64/mm/hugetlbpage.c   |  257 ---------------------------------
>  25-akpm/arch/sh/mm/hugetlbpage.c      |  258 ---------------------------------
>  25-akpm/arch/sparc64/mm/hugetlbpage.c |  259 ---------------------------------
>  25-akpm/fs/hugetlbfs/inode.c          |    2
>  25-akpm/include/linux/hugetlb.h       |    7
>  25-akpm/kernel/sysctl.c               |    6
>  25-akpm/mm/Makefile                   |    1
>  25-akpm/mm/hugetlb.c                  |  245 +++++++++++++++++++++++++++++++
>  10 files changed, 263 insertions(+), 1287 deletions(-)
>
> Of course, this buggers up everyone else's patches, but I do think this
> work has to come first.
>
> I still need to test this on ppc64 and ia64.  I've dropped a rollup against
> 2.6.5 at http://www.zip.com.au/~akpm/linux/patches/stuff/mc3.bz2 which you
> should work against until I get -mc3 out for real.

After bashing my poor bruised head against the screen for a
considerable period I've discovered that memset'ing your IO space
to zero is a very good way to stop your machine dead, silently.
Anyhow, here is a patch against -mc4 to make HUGETLB support actually
work in the presence of memory in ZONE_HIGHMEM.

-apw

== 8< =When clearing a large page allocation ensure we use a page clear function
which will correctly clear a ZONE_HIGHMEM page.

---
 hugetlb.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletion(-)

diff -upN reference/mm/hugetlb.c current/mm/hugetlb.c
--- reference/mm/hugetlb.c	2004-04-13 12:10:56.000000000 +0100
+++ current/mm/hugetlb.c	2004-04-13 12:12:20.000000000 +0100
@@ -9,6 +9,7 @@
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
 #include <linux/sysctl.h>
+#include <linux/highmem.h>

 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
 static unsigned long nr_huge_pages, free_huge_pages;
@@ -66,6 +67,7 @@ void free_huge_page(struct page *page)
 struct page *alloc_huge_page(void)
 {
 	struct page *page;
+	int i;

 	spin_lock(&hugetlb_lock);
 	page = dequeue_huge_page();
@@ -77,7 +79,8 @@ struct page *alloc_huge_page(void)
 	spin_unlock(&hugetlb_lock);
 	set_page_count(page, 1);
 	page->lru.prev = (void *)free_huge_page;
-	memset(page_address(page), 0, HPAGE_SIZE);
+	for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); ++i)
+		clear_highpage(&page[i]);
 	return page;
 }