linux-stable.git/include/linux/mm.h, branch v5.4.7

mm: thp: handle page cache THP correctly in PageTransCompoundMap

2019-11-06T16:28:58+00:00

We have a usecase to use tmpfs as QEMU memory backend and we would like
to take the advantage of THP as well.  But, our test shows the EPT is
not PMD mapped even though the underlying THP are PMD mapped on host.
The number showed by /sys/kernel/debug/kvm/largepage is much less than
the number of PMD mapped shmem pages as the below:

  7f2778200000-7f2878200000 rw-s 00000000 00:14 262232 /dev/shm/qemu_back_mem.mem.Hz2hSf (deleted)
  Size:            4194304 kB
  [snip]
  AnonHugePages:         0 kB
  ShmemPmdMapped:   579584 kB
  [snip]
  Locked:                0 kB

  cat /sys/kernel/debug/kvm/largepages
  12

And some benchmarks do worse than with anonymous THPs.

By digging into the code we figured out that commit 127393fbe597 ("mm:
thp: kvm: fix memory corruption in KVM with THP enabled") checks if
there is a single PTE mapping on the page for anonymous THP when setting
up EPT map.  But the _mapcount < 0 check doesn't work for page cache THP
since every subpage of page cache THP would get _mapcount inc'ed once it
is PMD mapped, so PageTransCompoundMap() always returns false for page
cache THP.  This would prevent KVM from setting up PMD mapped EPT entry.

So we need handle page cache THP correctly.  However, when page cache
THP's PMD gets split, kernel just remove the map instead of setting up
PTE map like what anonymous THP does.  Before KVM calls get_user_pages()
the subpages may get PTE mapped even though it is still a THP since the
page cache THP may be mapped by other processes at the mean time.

Checking its _mapcount and whether the THP has PTE mapped or not.
Although this may report some false negative cases (PTE mapped by other
processes), it looks not trivial to make this accurate.

With this fix /sys/kernel/debug/kvm/largepage would show reasonable
pages are PMD mapped by EPT as the below:

  7fbeaee00000-7fbfaee00000 rw-s 00000000 00:14 275464 /dev/shm/qemu_back_mem.mem.SKUvat (deleted)
  Size:            4194304 kB
  [snip]
  AnonHugePages:         0 kB
  ShmemPmdMapped:   557056 kB
  [snip]
  Locked:                0 kB

  cat /sys/kernel/debug/kvm/largepages
  271

And the benchmarks are as same as anonymous THPs.

[yang.shi@linux.alibaba.com: v4]
  Link: http://lkml.kernel.org/r/1571865575-42913-1-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1571769577-89735-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: dd78fedde4b9 ("rmap: support file thp")
Signed-off-by: Yang Shi 
Reported-by: Gang Deng 
Tested-by: Gang Deng 
Suggested-by: Hugh Dickins 
Acked-by: Kirill A. Shutemov 
Cc: Andrea Arcangeli 
Cc: Matthew Wilcox 
Cc: 	[4.8+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: treewide: clarify pgtable_page_{ctor,dtor}() naming

2019-09-26T17:10:44+00:00

The naming of pgtable_page_{ctor,dtor}() seems to have confused a few
people, and until recently arm64 used these erroneously/pointlessly for
other levels of page table.

To make it incredibly clear that these only apply to the PTE level, and to
align with the naming of pgtable_pmd_page_{ctor,dtor}(), let's rename them
to pgtable_pte_page_{ctor,dtor}().

These changes were generated with the following shell script:

----
git grep -lw 'pgtable_page_.tor' | while read FILE; do
    sed -i '{s/pgtable_page_ctor/pgtable_pte_page_ctor/}' $FILE;
    sed -i '{s/pgtable_page_dtor/pgtable_pte_page_dtor/}' $FILE;
done
----

... with the documentation re-flowed to remain under 80 columns, and
whitespace fixed up in macros to keep backslashes aligned.

There should be no functional change as a result of this patch.

Link: http://lkml.kernel.org/r/20190722141133.3116-1-mark.rutland@arm.com
Signed-off-by: Mark Rutland 
Reviewed-by: Mike Rapoport 
Acked-by: Geert Uytterhoeven 	[m68k]
Cc: Anshuman Khandual 
Cc: Matthew Wilcox 
Cc: Michal Hocko 
Cc: Yu Zhao 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, fs: move randomize_stack_top from fs to mm

2019-09-24T22:54:11+00:00

Patch series "Provide generic top-down mmap layout functions", v6.

This series introduces generic functions to make top-down mmap layout
easily accessible to architectures, in particular riscv which was the
initial goal of this series.  The generic implementation was taken from
arm64 and used successively by arm, mips and finally riscv.

Note that in addition the series fixes 2 issues:

- stack randomization was taken into account even if not necessary.

- [1] fixed an issue with mmap base which did not take into account
  randomization but did not report it to arm and mips, so by moving arm64
  into a generic library, this problem is now fixed for both
  architectures.

This work is an effort to factorize architecture functions to avoid code
duplication and oversights as in [1].

[1]: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html

This patch (of 14):

This preparatory commit moves this function so that further introduction
of generic topdown mmap layout is contained only in mm/util.c.

Link: http://lkml.kernel.org/r/20190730055113.23635-2-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti 
Acked-by: Kees Cook 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Luis Chamberlain 
Cc: Russell King 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Ralf Baechle 
Cc: Paul Burton 
Cc: James Hogan 
Cc: Palmer Dabbelt 
Cc: Albert Ou 
Cc: Alexander Viro 
Cc: Christoph Hellwig 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, thp: introduce FOLL_SPLIT_PMD

2019-09-24T22:54:11+00:00

Introduce a new foll_flag: FOLL_SPLIT_PMD.  As the name says
FOLL_SPLIT_PMD splits huge pmd for given mm_struct, the underlining huge
page stays as-is.

FOLL_SPLIT_PMD is useful for cases where we need to use regular pages, but
would switch back to huge page and huge pmd on.  One of such example is
uprobe.  The following patches use FOLL_SPLIT_PMD in uprobe.

Link: http://lkml.kernel.org/r/20190815164525.1848545-4-songliubraving@fb.com
Signed-off-by: Song Liu 
Reviewed-by: Oleg Nesterov 
Acked-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: move memcmp_pages() and pages_identical()

2019-09-24T22:54:11+00:00

Patch series "THP aware uprobe", v13.

This patchset makes uprobe aware of THPs.

Currently, when uprobe is attached to text on THP, the page is split by
FOLL_SPLIT.  As a result, uprobe eliminates the performance benefit of
THP.

This set makes uprobe THP-aware.  Instead of FOLL_SPLIT, we introduces
FOLL_SPLIT_PMD, which only split PMD for uprobe.

After all uprobes within the THP are removed, the PTE-mapped pages are
regrouped as huge PMD.

This set (plus a few THP patches) is also available at

   https://github.com/liu-song-6/linux/tree/uprobe-thp

This patch (of 6):

Move memcmp_pages() to mm/util.c and pages_identical() to mm.h, so that we
can use them in other files.

Link: http://lkml.kernel.org/r/20190815164525.1848545-2-songliubraving@fb.com
Signed-off-by: Song Liu 
Acked-by: Kirill A. Shutemov 
Reviewed-by: Oleg Nesterov 
Cc: Johannes Weiner 
Cc: Matthew Wilcox 
Cc: William Kucharski 
Cc: Srikar Dronamraju 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/gup: add make_dirty arg to put_user_pages_dirty_lock()

2019-09-24T22:54:08+00:00

[11~From: John Hubbard 
Subject: mm/gup: add make_dirty arg to put_user_pages_dirty_lock()

Patch series "mm/gup: add make_dirty arg to put_user_pages_dirty_lock()",
v3.

There are about 50+ patches in my tree [2], and I'll be sending out the
remaining ones in a few more groups:

* The block/bio related changes (Jerome mostly wrote those, but I've had
  to move stuff around extensively, and add a little code)

* mm/ changes

* other subsystem patches

* an RFC that shows the current state of the tracking patch set.  That
  can only be applied after all call sites are converted, but it's good to
  get an early look at it.

This is part a tree-wide conversion, as described in fc1d8e7cca2d ("mm:
introduce put_user_page*(), placeholder versions").

This patch (of 3):

Provide more capable variation of put_user_pages_dirty_lock(), and delete
put_user_pages_dirty().  This is based on the following:

1.  Lots of call sites become simpler if a bool is passed into
   put_user_page*(), instead of making the call site choose which
   put_user_page*() variant to call.

2.  Christoph Hellwig's observation that set_page_dirty_lock() is
   usually correct, and set_page_dirty() is usually a bug, or at least
   questionable, within a put_user_page*() calling chain.

This leads to the following API choices:

    * put_user_pages_dirty_lock(page, npages, make_dirty)

    * There is no put_user_pages_dirty(). You have to
      hand code that, in the rare case that it's
      required.

[jhubbard@nvidia.com: remove unused variable in siw_free_plist()]
  Link: http://lkml.kernel.org/r/20190729074306.10368-1-jhubbard@nvidia.com
Link: http://lkml.kernel.org/r/20190724044537.10458-2-jhubbard@nvidia.com
Signed-off-by: John Hubbard 
Cc: Matthew Wilcox 
Cc: Jan Kara 
Cc: Christoph Hellwig 
Cc: Ira Weiny 
Cc: Jason Gunthorpe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: introduce compound_nr()

2019-09-24T22:54:08+00:00

Replace 1 << compound_order(page) with compound_nr(page).  Minor
improvements in readability.

Link: http://lkml.kernel.org/r/20190721104612.19120-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Andrew Morton 
Reviewed-by: Ira Weiny 
Acked-by: Kirill A. Shutemov 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: introduce page_shift()

2019-09-24T22:54:08+00:00

Replace PAGE_SHIFT + compound_order(page) with the new page_shift()
function.  Minor improvements in readability.

[akpm@linux-foundation.org: fix build in tce_page_is_contained()]
  Link: http://lkml.kernel.org/r/201907241853.yNQTrJWd%25lkp@intel.com
Link: http://lkml.kernel.org/r/20190721104612.19120-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Andrew Morton 
Reviewed-by: Ira Weiny 
Acked-by: Kirill A. Shutemov 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: introduce page_size()

2019-09-24T22:54:08+00:00

Patch series "Make working with compound pages easier", v2.

These three patches add three helpers and convert the appropriate
places to use them.

This patch (of 3):

It's unnecessarily hard to find out the size of a potentially huge page.
Replace 'PAGE_SIZE << compound_order(page)' with page_size(page).

Link: http://lkml.kernel.org/r/20190721104612.19120-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Acked-by: Michal Hocko 
Reviewed-by: Andrew Morton 
Reviewed-by: Ira Weiny 
Acked-by: Kirill A. Shutemov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: add dummy can_do_mlock() helper

2019-09-24T22:54:06+00:00

On kernels without CONFIG_MMU, we get a link error for the siw driver:

drivers/infiniband/sw/siw/siw_mem.o: In function `siw_umem_get':
siw_mem.c:(.text+0x4c8): undefined reference to `can_do_mlock'

This is probably not the only driver that needs the function and could
otherwise build correctly without CONFIG_MMU, so add a dummy variant that
always returns false.

Link: http://lkml.kernel.org/r/20190909204201.931830-1-arnd@arndb.de
Fixes: 2251334dcac9 ("rdma/siw: application buffer management")
Signed-off-by: Arnd Bergmann 
Suggested-by: Jason Gunthorpe 
Acked-by: Michal Hocko 
Cc: Bernard Metzler 
Cc: "Matthew Wilcox (Oracle)" 
Cc: "Kirill A. Shutemov" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds