1. 22 1月, 2014 5 次提交
  2. 22 11月, 2013 2 次提交
    • A
      mm: hugetlbfs: fix hugetlbfs optimization · 27c73ae7
      Andrea Arcangeli 提交于
      Commit 7cb2ef56 ("mm: fix aio performance regression for database
      caused by THP") can cause dereference of a dangling pointer if
      split_huge_page runs during PageHuge() if there are updates to the
      tail_page->private field.
      
      Also it is repeating compound_head twice for hugetlbfs and it is running
      compound_head+compound_trans_head for THP when a single one is needed in
      both cases.
      
      The new code within the PageSlab() check doesn't need to verify that the
      THP page size is never bigger than the smallest hugetlbfs page size, to
      avoid memory corruption.
      
      A longstanding theoretical race condition was found while fixing the
      above (see the change right after the skip_unlock label, that is
      relevant for the compound_lock path too).
      
      By re-establishing the _mapcount tail refcounting for all compound
      pages, this also fixes the below problem:
      
        echo 0 >/sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
      
        BUG: Bad page state in process bash  pfn:59a01
        page:ffffea000139b038 count:0 mapcount:10 mapping:          (null) index:0x0
        page flags: 0x1c00000000008000(tail)
        Modules linked in:
        CPU: 6 PID: 2018 Comm: bash Not tainted 3.12.0+ #25
        Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
        Call Trace:
          dump_stack+0x55/0x76
          bad_page+0xd5/0x130
          free_pages_prepare+0x213/0x280
          __free_pages+0x36/0x80
          update_and_free_page+0xc1/0xd0
          free_pool_huge_page+0xc2/0xe0
          set_max_huge_pages.part.58+0x14c/0x220
          nr_hugepages_store_common.isra.60+0xd0/0xf0
          nr_hugepages_store+0x13/0x20
          kobj_attr_store+0xf/0x20
          sysfs_write_file+0x189/0x1e0
          vfs_write+0xc5/0x1f0
          SyS_write+0x55/0xb0
          system_call_fastpath+0x16/0x1b
      Signed-off-by: NKhalid Aziz <khalid.aziz@oracle.com>
      Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
      Tested-by: NKhalid Aziz <khalid.aziz@oracle.com>
      Cc: Pravin Shelar <pshelar@nicira.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Ben Hutchings <bhutchings@solarflare.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Johannes Weiner <jweiner@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      27c73ae7
    • D
      mm: thp: give transparent hugepage code a separate copy_page · 30b0a105
      Dave Hansen 提交于
      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 b32967ff ("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: NDave Hansen <dave.hansen@linux.intel.com>
      Acked-by: NMel Gorman <mgorman@suse.de>
      Reviewed-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Hillf Danton <dhillf@gmail.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Tested-by: NDave Jiang <dave.jiang@intel.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      30b0a105
  3. 15 11月, 2013 1 次提交
    • K
      mm, hugetlb: convert hugetlbfs to use split pmd lock · cb900f41
      Kirill A. Shutemov 提交于
      Hugetlb supports multiple page sizes. We use split lock only for PMD
      level, but not for PUD.
      
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Signed-off-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Tested-by: NAlex Thorlton <athorlton@sgi.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: "Eric W . Biederman" <ebiederm@xmission.com>
      Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Dave Jones <davej@redhat.com>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Michael Kerrisk <mtk.manpages@gmail.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Robin Holt <robinmholt@gmail.com>
      Cc: Sedat Dilek <sedat.dilek@gmail.com>
      Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Hugh Dickins <hughd@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      cb900f41
  4. 17 10月, 2013 2 次提交
    • A
      mm: hugetlb: initialize PG_reserved for tail pages of gigantic compound pages · ef5a22be
      Andrea Arcangeli 提交于
      Commit 11feeb49 ("kvm: optimize away THP checks in
      kvm_is_mmio_pfn()") introduced a memory leak when KVM is run on gigantic
      compound pages.
      
      That commit depends on the assumption that PG_reserved is identical for
      all head and tail pages of a compound page.  So that if get_user_pages
      returns a tail page, we don't need to check the head page in order to
      know if we deal with a reserved page that requires different
      refcounting.
      
      The assumption that PG_reserved is the same for head and tail pages is
      certainly correct for THP and regular hugepages, but gigantic hugepages
      allocated through bootmem don't clear the PG_reserved on the tail pages
      (the clearing of PG_reserved is done later only if the gigantic hugepage
      is freed).
      
      This patch corrects the gigantic compound page initialization so that we
      can retain the optimization in 11feeb49.  The cacheline was already
      modified in order to set PG_tail so this won't affect the boot time of
      large memory systems.
      
      [akpm@linux-foundation.org: tweak comment layout and grammar]
      Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
      Reported-by: Nandy123 <ajs124.ajs124@gmail.com>
      Acked-by: NRik van Riel <riel@redhat.com>
      Cc: Gleb Natapov <gleb@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Hugh Dickins <hughd@google.com>
      Acked-by: NRafael Aquini <aquini@redhat.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ef5a22be
    • J
      mm/hugetlb.c: correct missing private flag clearing · 16c794b4
      Joonsoo Kim 提交于
      We should clear the page's private flag when returing the page to the
      hugepage pool.  Otherwise, marked hugepage can be allocated to the user
      who tries to allocate the non-reserved hugepage.  If this user fail to
      map this hugepage, he would try to return the page to the hugepage pool.
      Since this page has a private flag, resv_huge_pages would mistakenly
      increase.  This patch fixes this situation.
      Signed-off-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Michal Hocko <mhocko@suse.cz>
      Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
      Cc: David Gibson <david@gibson.dropbear.id.au>
      Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Hillf Danton <dhillf@gmail.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      16c794b4
  5. 12 9月, 2013 20 次提交
  6. 16 8月, 2013 1 次提交
    • L
      Fix TLB gather virtual address range invalidation corner cases · 2b047252
      Linus Torvalds 提交于
      Ben Tebulin reported:
      
       "Since v3.7.2 on two independent machines a very specific Git
        repository fails in 9/10 cases on git-fsck due to an SHA1/memory
        failures.  This only occurs on a very specific repository and can be
        reproduced stably on two independent laptops.  Git mailing list ran
        out of ideas and for me this looks like some very exotic kernel issue"
      
      and bisected the failure to the backport of commit 53a59fc6 ("mm:
      limit mmu_gather batching to fix soft lockups on !CONFIG_PREEMPT").
      
      That commit itself is not actually buggy, but what it does is to make it
      much more likely to hit the partial TLB invalidation case, since it
      introduces a new case in tlb_next_batch() that previously only ever
      happened when running out of memory.
      
      The real bug is that the TLB gather virtual memory range setup is subtly
      buggered.  It was introduced in commit 597e1c35 ("mm/mmu_gather:
      enable tlb flush range in generic mmu_gather"), and the range handling
      was already fixed at least once in commit e6c495a9 ("mm: fix the TLB
      range flushed when __tlb_remove_page() runs out of slots"), but that fix
      was not complete.
      
      The problem with the TLB gather virtual address range is that it isn't
      set up by the initial tlb_gather_mmu() initialization (which didn't get
      the TLB range information), but it is set up ad-hoc later by the
      functions that actually flush the TLB.  And so any such case that forgot
      to update the TLB range entries would potentially miss TLB invalidates.
      
      Rather than try to figure out exactly which particular ad-hoc range
      setup was missing (I personally suspect it's the hugetlb case in
      zap_huge_pmd(), which didn't have the same logic as zap_pte_range()
      did), this patch just gets rid of the problem at the source: make the
      TLB range information available to tlb_gather_mmu(), and initialize it
      when initializing all the other tlb gather fields.
      
      This makes the patch larger, but conceptually much simpler.  And the end
      result is much more understandable; even if you want to play games with
      partial ranges when invalidating the TLB contents in chunks, now the
      range information is always there, and anybody who doesn't want to
      bother with it won't introduce subtle bugs.
      
      Ben verified that this fixes his problem.
      Reported-bisected-and-tested-by: NBen Tebulin <tebulin@googlemail.com>
      Build-testing-by: NStephen Rothwell <sfr@canb.auug.org.au>
      Build-testing-by: NRichard Weinberger <richard.weinberger@gmail.com>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Acked-by: NPeter Zijlstra <peterz@infradead.org>
      Cc: stable@vger.kernel.org
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2b047252
  7. 04 7月, 2013 2 次提交
    • J
      mm: correctly update zone->managed_pages · 3dcc0571
      Jiang Liu 提交于
      Enhance adjust_managed_page_count() to adjust totalhigh_pages for
      highmem pages.  And change code which directly adjusts totalram_pages to
      use adjust_managed_page_count() because it adjusts totalram_pages,
      totalhigh_pages and zone->managed_pages altogether in a safe way.
      
      Remove inc_totalhigh_pages() and dec_totalhigh_pages() from xen/balloon
      driver bacause adjust_managed_page_count() has already adjusted
      totalhigh_pages.
      
      This patch also fixes two bugs:
      
      1) enhances virtio_balloon driver to adjust totalhigh_pages when
         reserve/unreserve pages.
      2) enhance memory_hotplug.c to adjust totalhigh_pages when hot-removing
         memory.
      
      We still need to deal with modifications of totalram_pages in file
      arch/powerpc/platforms/pseries/cmm.c, but need help from PPC experts.
      
      [akpm@linux-foundation.org: remove ifdef, per Wanpeng Li, virtio_balloon.c cleanup, per Sergei]
      [akpm@linux-foundation.org: export adjust_managed_page_count() to modules, for drivers/virtio/virtio_balloon.c]
      Signed-off-by: NJiang Liu <jiang.liu@huawei.com>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: "Michael S. Tsirkin" <mst@redhat.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Jeremy Fitzhardinge <jeremy@goop.org>
      Cc: Wen Congyang <wency@cn.fujitsu.com>
      Cc: Tang Chen <tangchen@cn.fujitsu.com>
      Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
      Cc: Mel Gorman <mel@csn.ul.ie>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: <sworddragon2@aol.com>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Jianguo Wu <wujianguo@huawei.com>
      Cc: Joonsoo Kim <js1304@gmail.com>
      Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Marek Szyprowski <m.szyprowski@samsung.com>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Yinghai Lu <yinghai@kernel.org>
      Cc: Russell King <rmk@arm.linux.org.uk>
      Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3dcc0571
    • W
      mm/hugetlb: use already existing interface huge_page_shift · 2415cf12
      Wanpeng Li 提交于
      Use the already existing interface huge_page_shift instead of h->order +
      PAGE_SHIFT.
      Signed-off-by: NWanpeng Li <liwanp@linux.vnet.ibm.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Reviewed-by: NMichal Hocko <mhocko@suse.cz>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2415cf12
  8. 26 6月, 2013 1 次提交
    • Z
      futex: Take hugepages into account when generating futex_key · 13d60f4b
      Zhang Yi 提交于
      The futex_keys of process shared futexes are generated from the page
      offset, the mapping host and the mapping index of the futex user space
      address. This should result in an unique identifier for each futex.
      
      Though this is not true when futexes are located in different subpages
      of an hugepage. The reason is, that the mapping index for all those
      futexes evaluates to the index of the base page of the hugetlbfs
      mapping. So a futex at offset 0 of the hugepage mapping and another
      one at offset PAGE_SIZE of the same hugepage mapping have identical
      futex_keys. This happens because the futex code blindly uses
      page->index.
      
      Steps to reproduce the bug:
      
      1. Map a file from hugetlbfs. Initialize pthread_mutex1 at offset 0
         and pthread_mutex2 at offset PAGE_SIZE of the hugetlbfs
         mapping.
      
         The mutexes must be initialized as PTHREAD_PROCESS_SHARED because
         PTHREAD_PROCESS_PRIVATE mutexes are not affected by this issue as
         their keys solely depend on the user space address.
      
      2. Lock mutex1 and mutex2
      
      3. Create thread1 and in the thread function lock mutex1, which
         results in thread1 blocking on the locked mutex1.
      
      4. Create thread2 and in the thread function lock mutex2, which
         results in thread2 blocking on the locked mutex2.
      
      5. Unlock mutex2. Despite the fact that mutex2 got unlocked, thread2
         still blocks on mutex2 because the futex_key points to mutex1.
      
      To solve this issue we need to take the normal page index of the page
      which contains the futex into account, if the futex is in an hugetlbfs
      mapping. In other words, we calculate the normal page mapping index of
      the subpage in the hugetlbfs mapping.
      
      Mappings which are not based on hugetlbfs are not affected and still
      use page->index.
      
      Thanks to Mel Gorman who provided a patch for adding proper evaluation
      functions to the hugetlbfs code to avoid exposing hugetlbfs specific
      details to the futex code.
      
      [ tglx: Massaged changelog ]
      Signed-off-by: NZhang Yi <zhang.yi20@zte.com.cn>
      Reviewed-by: NJiang Biao <jiang.biao2@zte.com.cn>
      Tested-by: NMa Chenggong <ma.chenggong@zte.com.cn>
      Reviewed-by: N'Mel Gorman' <mgorman@suse.de>
      Acked-by: N'Darren Hart' <dvhart@linux.intel.com>
      Cc: 'Peter Zijlstra' <peterz@infradead.org>
      Cc: stable@vger.kernel.org
      Link: http://lkml.kernel.org/r/000101ce71a6%24a83c5880%24f8b50980%24@comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>
      13d60f4b
  9. 14 6月, 2013 2 次提交
  10. 13 6月, 2013 1 次提交
  11. 30 4月, 2013 2 次提交
    • D
      mm, hugetlb: include hugepages in meminfo · 949f7ec5
      David Rientjes 提交于
      Particularly in oom conditions, it's troublesome that hugetlb memory is
      not displayed.  All other meminfo that is emitted will not add up to
      what is expected, and there is no artifact left in the kernel log to
      show that a potentially significant amount of memory is actually
      allocated as hugepages which are not available to be reclaimed.
      
      Booting with hugepages=8192 on the command line, this memory is now
      shown in oom conditions.  For example, with echo m >
      /proc/sysrq-trigger:
      
        Node 0 hugepages_total=2048 hugepages_free=2048 hugepages_surp=0 hugepages_size=2048kB
        Node 1 hugepages_total=2048 hugepages_free=2048 hugepages_surp=0 hugepages_size=2048kB
        Node 2 hugepages_total=2048 hugepages_free=2048 hugepages_surp=0 hugepages_size=2048kB
        Node 3 hugepages_total=2048 hugepages_free=2048 hugepages_surp=0 hugepages_size=2048kB
      
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: NDavid Rientjes <rientjes@google.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      949f7ec5
    • G
      mm/hugetlb: add more arch-defined huge_pte functions · 106c992a
      Gerald Schaefer 提交于
      Commit abf09bed ("s390/mm: implement software dirty bits")
      introduced another difference in the pte layout vs.  the pmd layout on
      s390, thoroughly breaking the s390 support for hugetlbfs.  This requires
      replacing some more pte_xxx functions in mm/hugetlbfs.c with a
      huge_pte_xxx version.
      
      This patch introduces those huge_pte_xxx functions and their generic
      implementation in asm-generic/hugetlb.h, which will now be included on
      all architectures supporting hugetlbfs apart from s390.  This change
      will be a no-op for those architectures.
      
      [akpm@linux-foundation.org: fix warning]
      Signed-off-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Hillf Danton <dhillf@gmail.com>
      Acked-by: Michal Hocko <mhocko@suse.cz>	[for !s390 parts]
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Paul Mundt <lethal@linux-sh.org>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      106c992a
  12. 18 4月, 2013 1 次提交
    • N
      hugetlbfs: add swap entry check in follow_hugetlb_page() · 9cc3a5bd
      Naoya Horiguchi 提交于
      With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in
      initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory
      error happens on a hugepage and the affected processes try to access the
      error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0) in
      get_page().
      
      The reason for this bug is that coredump-related code doesn't recognise
      "hugepage hwpoison entry" with which a pmd entry is replaced when a memory
      error occurs on a hugepage.
      
      In other words, physical address information is stored in different bit
      layout between hugepage hwpoison entry and pmd entry, so
      follow_hugetlb_page() which is called in get_dump_page() returns a wrong
      page from a given address.
      
      The expected behavior is like this:
      
        absent   is_swap_pte   FOLL_DUMP   Expected behavior
        -------------------------------------------------------------------
         true     false         false       hugetlb_fault
         false    true          false       hugetlb_fault
         false    false         false       return page
         true     false         true        skip page (to avoid allocation)
         false    true          true        hugetlb_fault
         false    false         true        return page
      
      With this patch, we can call hugetlb_fault() and take proper actions (we
      wait for migration entries, fail with VM_FAULT_HWPOISON_LARGE for
      hwpoisoned entries,) and as the result we can dump all hugepages except
      for hwpoisoned ones.
      Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
      Cc: Rik van Riel <riel@redhat.com>
      Acked-by: NMichal Hocko <mhocko@suse.cz>
      Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
      Acked-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
      Acked-by: NDavid Rientjes <rientjes@google.com>
      Cc: <stable@vger.kernel.org>	[2.6.34+?]
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9cc3a5bd