On Sat, 28 Mar 2015, Andrey Korolyov wrote: > On Tue, Feb 24, 2015 at 3:12 AM, Marcelo Tosatti <mtosatti@xxxxxxxxxx> wrote: > > On Wed, Feb 04, 2015 at 08:34:04PM +0400, Andrey Korolyov wrote: > >> >Hi, > >> > > >> >I've seen the problem quite a few times. Before spending more time on > >> >it, I'd like to have a quick check here to see if anyone ever saw the > >> >same problem? Hope it is a relevant question with this mail list. > >> > > >> > > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.078623] BUG: unable to handle > >> >kernel NULL pointer dereference at 0000000000000008 > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.078916] IP: [<ffffffff8118d0fa>] > >> >copy_huge_page+0x8a/0x2a0 > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.079128] PGD 0 > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.079198] Oops: 0000 [#1] SMP > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.079319] Modules linked in: > >> >ip6table_filter ip6_tables ebtable_nat ebtables ipt_MASQUERADE > >> >iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 > >> >xt_state nf_conntrack ipt_REJECT xt_CHECKSUM iptable_mangle xt_tcpudp > >> >iptable_filter ip_tables x_tables kvm_intel kvm bridge stp llc ast ttm > >> >drm_kms_helper drm sysimgblt sysfillrect syscopyarea lp mei_me ioatdma > >> >ext2 parport mei shpchp dcdbas joydev mac_hid lpc_ich acpi_pad wmi > >> >hid_generic usbhid hid ixgbe igb dca i2c_algo_bit ahci ptp libahci > >> >mdio pps_core > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.081090] CPU: 19 PID: 3494 Comm: > >> >qemu-system-x86 Not tainted 3.11.0-15-generic #25~precise1-Ubuntu > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.081424] Hardware name: Dell Inc. > >> >PowerEdge C6220 II/09N44V, BIOS 2.0.3 07/03/2013 > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.081705] task: ffff881026750000 > >> >ti: ffff881026056000 task.ti: ffff881026056000 > >> >Jul 2 11:08:21 arno-3 kernel: [ 2165.081973] RIP: > >> >0010:[<ffffffff8118d0fa>] [<ffffffff8118d0fa>] > >> >copy_huge_page+0x8a/0x2a0 > >> > >> > >> Hello, > >> > >> sorry for possible top-posting, the same issue appears on at least > >> 3.10 LTS series. The original thread is at > >> http://marc.info/?l=kvm&m=14043742300901. > > > > Andrey, > > > > I am unable to access the URL above? > > > >> The necessary components for failure to reappear are a single running > >> kvm guest and mounted large thp: hugepagesz=1G (seemingly the same as > >> in initial report). With default 2M pages everything is working well, > >> the same for 3.18 with 1G THP. Are there any obvious clues for the > >> issue? > >> > >> Thanks! > > > > > > Hello, > > Marcelo, sorry, I`ve missed your reply in time. The working link, for > example is http://www.spinics.net/lists/linux-mm/msg75658.html. The > reproducer is a very simple, you need 1G THP and mounted hugetlbfs. > What is interesting, if guest is backed by THP like '-object > memory-backend-file,id=mem,size=1G,mem-path=/hugepages,share=on' the > failure is less likely to occur. I think you're mistaken when you write of "1G THP": although hugetlbfs can support 1G hugepages, we don't support that size with Transparent Huge Pages. But you are very appositely mistaken: copy_huge_page() used to make the same mistake, and Dave Hansen fixed it back in v3.13, but the fix never went to the stable trees. Your report was on an Ubuntu "3.11.0-15" kernel: I think Ubuntu have discontinued their 3.11-stable kernel series, but 3.10-longterm and 3.12-longterm would benefit from including this fix. I haven't tried patching and building and testing it there, but it looks reasonable. Hugh commit 30b0a105d9f7141e4cbf72ae5511832457d89788 Author: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Date: Thu Nov 21 14:31:58 2013 -0800 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@xxxxxxxxxxxxxxxxxxxx: fix coding-style and comment text, per Naoya Horiguchi] Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Cc: Hillf Danton <dhillf@xxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Tested-by: Dave Jiang <dave.jiang@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> 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) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 7d57af21f49e..2130365d387d 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 316e720a2023..bb940045fe85 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -442,6 +442,54 @@ 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) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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