On Mon, Oct 28, 2013 at 03:16:20PM -0700, Dave Hansen wrote: > > From: Dave Hansen <[email protected]> > > 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)) { > ... > > This patch creates a copy_high_order_page() which can > be used on THP pages.
We already have copy_user_huge_page() and copy_user_gigantic_page() in generic code (mm/memory.c). I think copy_gigantic_page() and copy_huge_page() should be moved there too. BTW, I think pages_per_huge_page in copy_user_huge_page() is redunand: compound_order(page) should be enough, right? -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
