From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756414AbbDGNbN (ORCPT ); Tue, 7 Apr 2015 09:31:13 -0400 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:54381 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754051AbbDGMwG (ORCPT ); Tue, 7 Apr 2015 08:52:06 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Dave Hansen , Hillf Danton , Andrea Arcangeli , Andrew Morton , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 023/155] mm: thp: give transparent hugepage code a separate copy_page Date: Tue, 7 Apr 2015 14:49:52 +0200 Message-Id: X-Mailer: git-send-email 2.3.4 In-Reply-To: <9a548862b8a26cbccc14f2c6c9c3688813d8d14b.1428411003.git.jslaby@suse.cz> References: <9a548862b8a26cbccc14f2c6c9c3688813d8d14b.1428411003.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 30b0a105d9f7141e4cbf72ae5511832457d89788 upstream. 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 Signed-off-by: Jiri Slaby --- include/linux/hugetlb.h | 4 ---- mm/hugetlb.c | 34 ---------------------------------- mm/migrate.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 48 insertions(+), 38 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 2a943a396d20..1eaf61dde2c3 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -70,7 +70,6 @@ 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); @@ -149,9 +148,6 @@ static inline bool isolate_huge_page(struct page *page, struct list_head *list) } #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) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 1b040cb0ac5b..b43467a88243 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -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); diff --git a/mm/migrate.c b/mm/migrate.c index 66ca0c494b90..05502f10c842 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -444,6 +444,54 @@ int migrate_huge_page_move_mapping(struct address_space *mapping, } /* + * 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 */ void migrate_page_copy(struct page *newpage, struct page *page) -- 2.3.4