On Sun, Mar 29, 2015 at 3:25 AM, Hugh Dickins <hughd@xxxxxxxxxx> wrote: > 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) Thanks, the issue is fixed on 3.10 with trivial patch modification. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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