On Sat, 28 Mar 2015, Andrey Korolyov wrote:
> On Tue, Feb 24, 2015 at 3:12 AM, Marcelo Tosatti <mtosa...@redhat.com> 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.han...@linux.intel.com>
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")
[a...@linux-foundation.org: fix coding-style and comment text, per Naoya
Horiguchi]
Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
Acked-by: Mel Gorman <mgor...@suse.de>
Reviewed-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
Cc: Hillf Danton <dhi...@gmail.com>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Tested-by: Dave Jiang <dave.ji...@intel.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
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)
--
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