From 30b0a105d9f7141e4cbf72ae5511832457d89788 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Thu, 21 Nov 2013 14:31:58 -0800 Subject: 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 b32967ff101a ("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: Dave Hansen Acked-by: Mel Gorman Reviewed-by: Naoya Horiguchi Cc: Hillf Danton Cc: Andrea Arcangeli Tested-by: Dave Jiang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/hugetlb.h | 4 ---- 1 file changed, 4 deletions(-) (limited to 'include/linux/hugetlb.h') diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index acd2010328f3..85e0c58bdfdf 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -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) -- cgit