linux.git/mm, branch v4.8-rc6

Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

2016-09-10T16:58:52+00:00

Pull libnvdimm fixes from Dan Williams:
 "nvdimm fixes for v4.8, two of them are tagged for -stable:

   - Fix devm_memremap_pages() to use track_pfn_insert().  Otherwise,
     DAX pmd mappings end up with an uncached pgprot, and unusable
     performance for the device-dax interface.  The device-dax interface
     appeared in 4.7 so this is tagged for -stable.

   - Fix a couple VM_BUG_ON() checks in the show_smaps() path to
     understand DAX pmd entries.  This fix is tagged for -stable.

   - Fix a mis-merge of the nfit machine-check handler to flip the
     polarity of an if() to match the final version of the patch that
     Vishal sent for 4.8-rc1.  Without this the nfit machine check
     handler never detects / inserts new 'badblocks' entries which
     applications use to identify lost portions of files.

   - For test purposes, fix the nvdimm_clear_poison() path to operate on
     legacy / simulated nvdimm memory ranges.  Without this fix a test
     can set badblocks, but never clear them on these ranges.

   - Fix the range checking done by dax_dev_pmd_fault().  This is not
     tagged for -stable since this problem is mitigated by specifying
     aligned resources at device-dax setup time.

  These patches have appeared in a next release over the past week.  The
  recent rebase you can see in the timestamps was to drop an invalid fix
  as identified by the updated device-dax unit tests [1].  The -mm
  touches have an ack from Andrew"

[1]: "[ndctl PATCH 0/3] device-dax test for recent kernel bugs"
   https://lists.01.org/pipermail/linux-nvdimm/2016-September/006855.html

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  libnvdimm: allow legacy (e820) pmem region to clear bad blocks
  nfit, mce: Fix SPA matching logic in MCE handler
  mm: fix cache mode of dax pmd mappings
  mm: fix show_smap() for zone_device-pmd ranges
  dax: fix mapping size check

mm: fix show_smap() for zone_device-pmd ranges

2016-09-10T00:34:45+00:00

Attempting to dump /proc//smaps for a process with pmd dax mappings
currently results in the following VM_BUG_ONs:

 kernel BUG at mm/huge_memory.c:1105!
 task: ffff88045f16b140 task.stack: ffff88045be14000
 RIP: 0010:[]  [] follow_trans_huge_pmd+0x2cb/0x340
 [..]
 Call Trace:
  [] smaps_pte_range+0xa0/0x4b0
  [] ? vsnprintf+0x255/0x4c0
  [] __walk_page_range+0x1fe/0x4d0
  [] walk_page_vma+0x62/0x80
  [] show_smap+0xa6/0x2b0

 kernel BUG at fs/proc/task_mmu.c:585!
 RIP: 0010:[]  [] smaps_pte_range+0x499/0x4b0
 Call Trace:
  [] ? vsnprintf+0x255/0x4c0
  [] __walk_page_range+0x1fe/0x4d0
  [] walk_page_vma+0x62/0x80
  [] show_smap+0xa6/0x2b0

These locations are sanity checking page flags that must be set for an
anonymous transparent huge page, but are not set for the zone_device
pages associated with dax mappings.

Cc: Ross Zwisler 
Cc: Kirill A. Shutemov 
Acked-by: Andrew Morton 
Signed-off-by: Dan Williams

usercopy: remove page-spanning test for now

2016-09-07T18:33:26+00:00

A custom allocator without __GFP_COMP that copies to userspace has been
found in vmw_execbuf_process[1], so this disables the page-span checker
by placing it behind a CONFIG for future work where such things can be
tracked down later.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1373326

Reported-by: Vinson Lee 
Fixes: f5509cc18daa ("mm: Hardened usercopy")
Signed-off-by: Kees Cook

mm, mempolicy: task->mempolicy must be NULL before dropping final reference

2016-09-02T00:52:01+00:00

KASAN allocates memory from the page allocator as part of
kmem_cache_free(), and that can reference current->mempolicy through any
number of allocation functions.  It needs to be NULL'd out before the
final reference is dropped to prevent a use-after-free bug:

	BUG: KASAN: use-after-free in alloc_pages_current+0x363/0x370 at addr ffff88010b48102c
	CPU: 0 PID: 15425 Comm: trinity-c2 Not tainted 4.8.0-rc2+ #140
	...
	Call Trace:
		dump_stack
		kasan_object_err
		kasan_report_error
		__asan_report_load2_noabort
		alloc_pages_current	<-- use after free
		depot_save_stack
		save_stack
		kasan_slab_free
		kmem_cache_free
		__mpol_put		<-- free
		do_exit

This patch sets current->mempolicy to NULL before dropping the final
reference.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1608301442180.63329@chino.kir.corp.google.com
Fixes: cd11016e5f52 ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB")
Signed-off-by: David Rientjes 
Reported-by: Vegard Nossum 
Acked-by: Andrey Ryabinin 
Cc: Alexander Potapenko 
Cc: Dmitry Vyukov 
Cc: 	[4.6+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator

2016-09-02T00:52:01+00:00

Firmware Assisted Dump (FA_DUMP) on ppc64 reserves substantial amounts
of memory when booting a secondary kernel.  Srikar Dronamraju reported
that multiple nodes may have no memory managed by the buddy allocator
but still return true for populated_zone().

Commit 1d82de618ddd ("mm, vmscan: make kswapd reclaim in terms of
nodes") was reported to cause kswapd to spin at 100% CPU usage when
fadump was enabled.  The old code happened to deal with the situation of
a populated node with zero free pages by co-incidence but the current
code tries to reclaim populated zones without realising that is
impossible.

We cannot just convert populated_zone() as many existing users really
need to check for present_pages.  This patch introduces a managed_zone()
helper and uses it in the few cases where it is critical that the check
is made for managed pages -- zonelist construction and page reclaim.

Link: http://lkml.kernel.org/r/20160831195104.GB8119@techsingularity.net
Signed-off-by: Mel Gorman 
Reported-by: Srikar Dronamraju 
Tested-by: Srikar Dronamraju 
Acked-by: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, oom: prevent premature OOM killer invocation for high order request

2016-09-02T00:52:01+00:00

There have been several reports about pre-mature OOM killer invocation
in 4.7 kernel when order-2 allocation request (for the kernel stack)
invoked OOM killer even during basic workloads (light IO or even kernel
compile on some filesystems).  In all reported cases the memory is
fragmented and there are no order-2+ pages available.  There is usually
a large amount of slab memory (usually dentries/inodes) and further
debugging has shown that there are way too many unmovable blocks which
are skipped during the compaction.  Multiple reporters have confirmed
that the current linux-next which includes [1] and [2] helped and OOMs
are not reproducible anymore.

A simpler fix for the late rc and stable is to simply ignore the
compaction feedback and retry as long as there is a reclaim progress and
we are not getting OOM for order-0 pages.  We already do that for
CONFING_COMPACTION=n so let's reuse the same code when compaction is
enabled as well.

[1] http://lkml.kernel.org/r/20160810091226.6709-1-vbabka@suse.cz
[2] http://lkml.kernel.org/r/f7a9ea9d-bb88-bfd6-e340-3a933559305a@suse.cz

Fixes: 0a0337e0d1d1 ("mm, oom: rework oom detection")
Link: http://lkml.kernel.org/r/20160823074339.GB23577@dhcp22.suse.cz
Signed-off-by: Michal Hocko 
Tested-by: Olaf Hering 
Tested-by: Ralf-Peter Rohbeck 
Cc: Markus Trippelsdorf 
Cc: Arkadiusz Miskiewicz 
Cc: Ralf-Peter Rohbeck 
Cc: Jiri Slaby 
Cc: Vlastimil Babka 
Cc: Joonsoo Kim 
Cc: Tetsuo Handa 
Cc: David Rientjes 
Cc: 	[4.7.x]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: silently skip readahead for DAX inodes

2016-08-27T00:39:35+00:00

For DAX inodes we need to be careful to never have page cache pages in
the mapping->page_tree.  This radix tree should be composed only of DAX
exceptional entries and zero pages.

ltp's readahead02 test was triggering a warning because we were trying
to insert a DAX exceptional entry but found that a page cache page had
already been inserted into the tree.  This page was being inserted into
the radix tree in response to a readahead(2) call.

Readahead doesn't make sense for DAX inodes, but we don't want it to
report a failure either.  Instead, we just return success and don't do
any work.

Link: http://lkml.kernel.org/r/20160824221429.21158-1-ross.zwisler@linux.intel.com
Signed-off-by: Ross Zwisler 
Reported-by: Jeff Moyer 
Cc: Dan Williams 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: Jan Kara 
Cc: 	[4.5+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memcontrol: avoid unused function warning

2016-08-27T00:39:35+00:00

A bugfix in v4.8-rc2 introduced a harmless warning when
CONFIG_MEMCG_SWAP is disabled but CONFIG_MEMCG is enabled:

  mm/memcontrol.c:4085:27: error: 'mem_cgroup_id_get_online' defined but not used [-Werror=unused-function]
   static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)

This moves the function inside of the #ifdef block that hides the
calling function, to avoid the warning.

Fixes: 1f47b61fb407 ("mm: memcontrol: fix swap counter leak on swapout from offline cgroup")
Link: http://lkml.kernel.org/r/20160824113733.2776701-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann 
Acked-by: Michal Hocko 
Acked-by: Vladimir Davydov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: clarify COMPACTION Kconfig text

2016-08-27T00:39:35+00:00

The current wording of the COMPACTION Kconfig help text doesn't
emphasise that disabling COMPACTION might cripple the page allocator
which relies on the compaction quite heavily for high order requests and
an unexpected OOM can happen with the lack of compaction.  Make sure we
are vocal about that.

Link: http://lkml.kernel.org/r/20160823091726.GK23577@dhcp22.suse.cz
Signed-off-by: Michal Hocko 
Cc: Markus Trippelsdorf 
Cc: Mel Gorman 
Cc: Joonsoo Kim 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

soft_dirty: fix soft_dirty during THP split

2016-08-27T00:39:35+00:00

While adding proper userfaultfd_wp support with bits in pagetable and
swap entry to avoid false positives WP userfaults through swap/fork/
KSM/etc, I've been adding a framework that mostly mirrors soft dirty.

So I noticed in one place I had to add uffd_wp support to the pagetables
that wasn't covered by soft_dirty and I think it should have.

Example: in the THP migration code migrate_misplaced_transhuge_page()
pmd_mkdirty is called unconditionally after mk_huge_pmd.

	entry = mk_huge_pmd(new_page, vma->vm_page_prot);
	entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);

That sets soft dirty too (it's a false positive for soft dirty, the soft
dirty bit could be more finegrained and transfer the bit like uffd_wp
will do..  pmd/pte_uffd_wp() enforces the invariant that when it's set
pmd/pte_write is not set).

However in the THP split there's no unconditional pmd_mkdirty after
mk_huge_pmd and pte_swp_mksoft_dirty isn't called after the migration
entry is created.  The code sets the dirty bit in the struct page
instead of setting it in the pagetable (which is fully equivalent as far
as the real dirty bit is concerned, as the whole point of pagetable bits
is to be eventually flushed out of to the page, but that is not
equivalent for the soft-dirty bit that gets lost in translation).

This was found by code review only and totally untested as I'm working
to actually replace soft dirty and I don't have time to test potential
soft dirty bugfixes as well :).

Transfer the soft_dirty from pmd to pte during THP splits.

This fix avoids losing the soft_dirty bit and avoids userland memory
corruption in the checkpoint.

Fixes: eef1b3ba053aa6 ("thp: implement split_huge_pmd()")
Link: http://lkml.kernel.org/r/1471610515-30229-2-git-send-email-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli 
Acked-by: Pavel Emelyanov 
Cc: "Kirill A. Shutemov" 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds