Commit 30b0a105 authored by Dave Hansen's avatar Dave Hansen Committed by Linus Torvalds

mm: thp: give transparent hugepage code a separate copy_page

Right now, the migration code in migrate_page_copy() uses copy_huge_page()
for hugetlbfs and thp pages:

       if (PageHuge(page) || PageTransHuge(page))
                copy_huge_page(newpage, page);

So, yay for code reuse.  But:

  void copy_huge_page(struct page *dst, struct page *src)
  {
        struct hstate *h = page_hstate(src);

and a non-hugetlbfs page has no page_hstate().  This works 99% of the
time because page_hstate() determines the hstate from the page order
alone.  Since the page order of a THP page matches the default hugetlbfs
page order, it works.

But, if you change the default huge page size on the boot command-line
(say default_hugepagesz=1G), then we might not even *have* a 2MB hstate
so page_hstate() returns null and copy_huge_page() oopses pretty fast
since copy_huge_page() dereferences the hstate:

  void copy_huge_page(struct page *dst, struct page *src)
  {
        struct hstate *h = page_hstate(src);
        if (unlikely(pages_per_huge_page(h) > MAX_ORDER_NR_PAGES)) {
  ...

Mel noticed that the migration code is really the only user of these
functions.  This moves all the copy code over to migrate.c and makes
copy_huge_page() work for THP by checking for it explicitly.

I believe the bug was introduced in commit b32967ff ("mm: numa: Add
THP migration for the NUMA working set scanning fault case")

[akpm@linux-foundation.org: fix coding-style and comment text, per Naoya Horiguchi]
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Tested-by: default avatarDave Jiang <dave.jiang@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c11230f4
......@@ -69,7 +69,6 @@ int dequeue_hwpoisoned_huge_page(struct page *page);
bool isolate_huge_page(struct page *page, struct list_head *list);
void putback_active_hugepage(struct page *page);
bool is_hugepage_active(struct page *page);
void copy_huge_page(struct page *dst, struct page *src);
#ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud);
......@@ -140,9 +139,6 @@ static inline int dequeue_hwpoisoned_huge_page(struct page *page)
#define isolate_huge_page(p, l) false
#define putback_active_hugepage(p) do {} while (0)
#define is_hugepage_active(x) false
static inline void copy_huge_page(struct page *dst, struct page *src)
{
}
static inline unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
unsigned long address, unsigned long end, pgprot_t newprot)
......
......@@ -476,40 +476,6 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg)
return 0;
}
static void copy_gigantic_page(struct page *dst, struct page *src)
{
int i;
struct hstate *h = page_hstate(src);
struct page *dst_base = dst;
struct page *src_base = src;
for (i = 0; i < pages_per_huge_page(h); ) {
cond_resched();
copy_highpage(dst, src);
i++;
dst = mem_map_next(dst, dst_base, i);
src = mem_map_next(src, src_base, i);
}
}
void copy_huge_page(struct page *dst, struct page *src)
{
int i;
struct hstate *h = page_hstate(src);
if (unlikely(pages_per_huge_page(h) > MAX_ORDER_NR_PAGES)) {
copy_gigantic_page(dst, src);
return;
}
might_sleep();
for (i = 0; i < pages_per_huge_page(h); i++) {
cond_resched();
copy_highpage(dst + i, src + i);
}
}
static void enqueue_huge_page(struct hstate *h, struct page *page)
{
int nid = page_to_nid(page);
......
......@@ -441,6 +441,54 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
return MIGRATEPAGE_SUCCESS;
}
/*
* Gigantic pages are so large that we do not guarantee that page++ pointer
* arithmetic will work across the entire page. We need something more
* specialized.
*/
static void __copy_gigantic_page(struct page *dst, struct page *src,
int nr_pages)
{
int i;
struct page *dst_base = dst;
struct page *src_base = src;
for (i = 0; i < nr_pages; ) {
cond_resched();
copy_highpage(dst, src);
i++;
dst = mem_map_next(dst, dst_base, i);
src = mem_map_next(src, src_base, i);
}
}
static void copy_huge_page(struct page *dst, struct page *src)
{
int i;
int nr_pages;
if (PageHuge(src)) {
/* hugetlbfs page */
struct hstate *h = page_hstate(src);
nr_pages = pages_per_huge_page(h);
if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
__copy_gigantic_page(dst, src, nr_pages);
return;
}
} else {
/* thp page */
BUG_ON(!PageTransHuge(src));
nr_pages = hpage_nr_pages(src);
}
for (i = 0; i < nr_pages; i++) {
cond_resched();
copy_highpage(dst + i, src + i);
}
}
/*
* Copy the page to its new location
*/
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment