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  1. 22 2月, 2019 4 次提交
  3. 18 2月, 2019 1 次提交
  5. 16 2月, 2019 1 次提交
    • A
      arm64, mm, efi: Account for GICv3 LPI tables in static memblock reserve table · 8a5b403d
      由 Ard Biesheuvel 提交于 
      In the irqchip and EFI code, we have what basically amounts to a quirk
to work around a peculiarity in the GICv3 architecture, which permits
the system memory address of LPI tables to be programmable only once
after a CPU reset. This means kexec kernels must use the same memory
as the first kernel, and thus ensure that this memory has not been
given out for other purposes by the time the ITS init code runs, which
is not very early for secondary CPUs.

On systems with many CPUs, these reservations could overflow the
memblock reservation table, and this was addressed in commit:

  eff89628 ("efi/arm: Defer persistent reservations until after paging_init()")

However, this turns out to have made things worse, since the allocation
of page tables and heap space for the resized memblock reservation table
itself may overwrite the regions we are attempting to reserve, which may
cause all kinds of corruption, also considering that the ITS will still
be poking bits into that memory in response to incoming MSIs.

So instead, let's grow the static memblock reservation table on such
systems so it can accommodate these reservations at an earlier time.
This will permit us to revert the above commit in a subsequent patch.

[ mingo: Minor cleanups. ]
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: NMike Rapoport <rppt@linux.ibm.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20190215123333.21209-2-ard.biesheuvel@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      8a5b403d
  7. 15 2月, 2019 1 次提交
    • J
      mm: page_alloc: fix ref bias in page_frag_alloc() for 1-byte allocs · 2c2ade81
      由 Jann Horn 提交于 
      The basic idea behind ->pagecnt_bias is: If we pre-allocate the maximum
number of references that we might need to create in the fastpath later,
the bump-allocation fastpath only has to modify the non-atomic bias value
that tracks the number of extra references we hold instead of the atomic
refcount. The maximum number of allocations we can serve (under the
assumption that no allocation is made with size 0) is nc->size, so that's
the bias used.

However, even when all memory in the allocation has been given away, a
reference to the page is still held; and in the `offset < 0` slowpath, the
page may be reused if everyone else has dropped their references.
This means that the necessary number of references is actually
`nc->size+1`.

Luckily, from a quick grep, it looks like the only path that can call
page_frag_alloc(fragsz=1) is TAP with the IFF_NAPI_FRAGS flag, which
requires CAP_NET_ADMIN in the init namespace and is only intended to be
used for kernel testing and fuzzing.

To test for this issue, put a `WARN_ON(page_ref_count(page) == 0)` in the
`offset < 0` path, below the virt_to_page() call, and then repeatedly call
writev() on a TAP device with IFF_TAP|IFF_NO_PI|IFF_NAPI_FRAGS|IFF_NAPI,
with a vector consisting of 15 elements containing 1 byte each.
Signed-off-by: NJann Horn <jannh@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      2c2ade81
  9. 13 2月, 2019 3 次提交
    • Q
      Revert "mm: use early_pfn_to_nid in page_ext_init" · 2f1ee091
      由 Qian Cai 提交于 
      This reverts commit fe53ca54 ("mm: use early_pfn_to_nid in
page_ext_init").

When booting a system with "page_owner=on",

start_kernel
  page_ext_init
    invoke_init_callbacks
      init_section_page_ext
        init_page_owner
          init_early_allocated_pages
            init_zones_in_node
              init_pages_in_zone
                lookup_page_ext
                  page_to_nid

The issue here is that page_to_nid() will not work since some page flags
have no node information until later in page_alloc_init_late() due to
DEFERRED_STRUCT_PAGE_INIT.  Hence, it could trigger an out-of-bounds
access with an invalid nid.

  UBSAN: Undefined behaviour in ./include/linux/mm.h:1104:50
  index 7 is out of range for type 'zone [5]'

Also, kernel will panic since flags were poisoned earlier with,

CONFIG_DEBUG_VM_PGFLAGS=y
CONFIG_NODE_NOT_IN_PAGE_FLAGS=n

start_kernel
  setup_arch
    pagetable_init
      paging_init
        sparse_init
          sparse_init_nid
            memblock_alloc_try_nid_raw

It did not handle it well in init_pages_in_zone() which ends up calling
page_to_nid().

  page:ffffea0004200000 is uninitialized and poisoned
  raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
  raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
  page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
  page_owner info is not active (free page?)
  kernel BUG at include/linux/mm.h:990!
  RIP: 0010:init_page_owner+0x486/0x520

This means that assumptions behind commit fe53ca54 ("mm: use
early_pfn_to_nid in page_ext_init") are incomplete.  Therefore, revert
the commit for now.  A proper way to move the page_owner initialization
to sooner is to hook into memmap initialization.

Link: http://lkml.kernel.org/r/20190115202812.75820-1-cai@lca.pwSigned-off-by: NQian Cai <cai@lca.pw>
Acked-by: NMichal Hocko <mhocko@kernel.org>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2f1ee091
    • Y
      mm/gup: fix gup_pmd_range() for dax · 414fd080
      由 Yu Zhao 提交于 
      For dax pmd, pmd_trans_huge() returns false but pmd_huge() returns true
on x86.  So the function works as long as hugetlb is configured.
However, dax doesn't depend on hugetlb.

Link: http://lkml.kernel.org/r/20190111034033.601-1-yuzhao@google.comSigned-off-by: NYu Zhao <yuzhao@google.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Keith Busch <keith.busch@intel.com>
Cc: "Michael S . Tsirkin" <mst@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      414fd080
    • D
      Revert "mm: slowly shrink slabs with a relatively small number of objects" · a9a238e8
      由 Dave Chinner 提交于 
      This reverts commit 172b06c3 ("mm: slowly shrink slabs with a
relatively small number of objects").

This change changes the agressiveness of shrinker reclaim, causing small
cache and low priority reclaim to greatly increase scanning pressure on
small caches.  As a result, light memory pressure has a disproportionate
affect on small caches, and causes large caches to be reclaimed much
faster than previously.

As a result, it greatly perturbs the delicate balance of the VFS caches
(dentry/inode vs file page cache) such that the inode/dentry caches are
reclaimed much, much faster than the page cache and this drives us into
several other caching imbalance related problems.

As such, this is a bad change and needs to be reverted.

[ Needs some massaging to retain the later seekless shrinker
  modifications.]

Link: http://lkml.kernel.org/r/20190130041707.27750-3-david@fromorbit.com
Fixes: 172b06c3 ("mm: slowly shrink slabs with a relatively small number of objects")
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Cc: Wolfgang Walter <linux@stwm.de>
Cc: Roman Gushchin <guro@fb.com>
Cc: Spock <dairinin@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a9a238e8
  11. 02 2月, 2019 12 次提交
  13. 29 1月, 2019 1 次提交
    • M
      Revert "mm, memory_hotplug: initialize struct pages for the full memory section" · 4aa9fc2a
      由 Michal Hocko 提交于 
      This reverts commit 2830bf6f.

The underlying assumption that one sparse section belongs into a single
numa node doesn't hold really. Robert Shteynfeld has reported a boot
failure. The boot log was not captured but his memory layout is as
follows:

  Early memory node ranges
    node   1: [mem 0x0000000000001000-0x0000000000090fff]
    node   1: [mem 0x0000000000100000-0x00000000dbdf8fff]
    node   1: [mem 0x0000000100000000-0x0000001423ffffff]
    node   0: [mem 0x0000001424000000-0x0000002023ffffff]

This means that node0 starts in the middle of a memory section which is
also in node1.  memmap_init_zone tries to initialize padding of a
section even when it is outside of the given pfn range because there are
code paths (e.g.  memory hotplug) which assume that the full worth of
memory section is always initialized.

In this particular case, though, such a range is already intialized and
most likely already managed by the page allocator.  Scribbling over
those pages corrupts the internal state and likely blows up when any of
those pages gets used.
Reported-by: NRobert Shteynfeld <robert.shteynfeld@gmail.com>
Fixes: 2830bf6f ("mm, memory_hotplug: initialize struct pages for the full memory section")
Cc: stable@kernel.org
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4aa9fc2a
  15. 24 1月, 2019 1 次提交
    • L
      Revert "Change mincore() to count "mapped" pages rather than "cached" pages" · 30bac164
      由 Linus Torvalds 提交于 
      This reverts commit 574823bf.

It turns out that my hope that we could just remove the code that
exposes the cache residency status from mincore() was too optimistic.

There are various random users that want it, and one example would be
the Netflix database cluster maintenance. To quote Josh Snyder:

 "For Netflix, losing accurate information from the mincore syscall
  would lengthen database cluster maintenance operations from days to
  months. We rely on cross-process mincore to migrate the contents of a
  page cache from machine to machine, and across reboots.

  To do this, I wrote and maintain happycache [1], a page cache
  dumper/loader tool. It is quite similar in architecture to pgfincore,
  except that it is agnostic to workload. The gist of happycache's
  operation is "produce a dump of residence status for each page, do
  some operation, then reload exactly the same pages which were present
  before." happycache is entirely dependent on accurate reporting of the
  in-core status of file-backed pages, as accessed by another process.

  We primarily use happycache with Cassandra, which (like Postgres +
  pgfincore) relies heavily on OS page cache to reduce disk accesses.
  Because our workloads never experience a cold page cache, we are able
  to provision hardware for a peak utilization level that is far lower
  than the hypothetical "every query is a cache miss" peak.

  A database warmed by happycache can be ready for service in seconds
  (bounded only by the performance of the drives and the I/O subsystem),
  with no period of in-service degradation. By contrast, putting a
  database in service without a page cache entails a potentially
  unbounded period of degradation (at Netflix, the time to populate a
  single node's cache via natural cache misses varies by workload from
  hours to weeks). If a single node upgrade were to take weeks, then
  upgrading an entire cluster would take months. Since we want to apply
  security upgrades (and other things) on a somewhat tighter schedule,
  we would have to develop more complex solutions to provide the same
  functionality already provided by mincore.

  At the bottom line, happycache is designed to benignly exploit the
  same information leak documented in the paper [2]. I think it makes
  perfect sense to remove cross-process mincore functionality from
  unprivileged users, but not to remove it entirely"

We do have an alternate approach that limits the cache residency
reporting only to processes that have write permissions to the file, so
we can fix the original information leak issue that way.  It involves
_adding_ code rather than removing it, which is sad, but hey, at least
we haven't found any users that would find the restrictions
unacceptable.

So revert the optimistic first approach to make room for that alternate
fix instead.
Reported-by: NJosh Snyder <joshs@netflix.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Kevin Easton <kevin@guarana.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Cyril Hrubis <chrubis@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Daniel Gruss <daniel@gruss.cc>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      30bac164
  17. 23 1月, 2019 1 次提交
  19. 10 1月, 2019 1 次提交
  21. 09 1月, 2019 11 次提交
  23. 07 1月, 2019 1 次提交
    • L
      Change mincore() to count "mapped" pages rather than "cached" pages · 574823bf
      由 Linus Torvalds 提交于 
      The semantics of what "in core" means for the mincore() system call are
somewhat unclear, but Linux has always (since 2.3.52, which is when
mincore() was initially done) treated it as "page is available in page
cache" rather than "page is mapped in the mapping".

The problem with that traditional semantic is that it exposes a lot of
system cache state that it really probably shouldn't, and that users
shouldn't really even care about.

So let's try to avoid that information leak by simply changing the
semantics to be that mincore() counts actual mapped pages, not pages
that might be cheaply mapped if they were faulted (note the "might be"
part of the old semantics: being in the cache doesn't actually guarantee
that you can access them without IO anyway, since things like network
filesystems may have to revalidate the cache before use).

In many ways the old semantics were somewhat insane even aside from the
information leak issue.  From the very beginning (and that beginning is
a long time ago: 2.3.52 was released in March 2000, I think), the code
had a comment saying

  Later we can get more picky about what "in core" means precisely.

and this is that "later".  Admittedly it is much later than is really
comfortable.

NOTE! This is a real semantic change, and it is for example known to
change the output of "fincore", since that program literally does a
mmmap without populating it, and then doing "mincore()" on that mapping
that doesn't actually have any pages in it.

I'm hoping that nobody actually has any workflow that cares, and the
info leak is real.

We may have to do something different if it turns out that people have
valid reasons to want the old semantics, and if we can limit the
information leak sanely.

Cc: Kevin Easton <kevin@guarana.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Masatake YAMATO <yamato@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      574823bf
  25. 05 1月, 2019 2 次提交