We want to switch to allocating them runtime only when hash translation is
enabled. Add helpers so that both book3s and nohash can be adapted to
upcoming change easily.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

When doing top-down search the low_limit is not PAGE_SIZE but rather
max(PAGE_SIZE, mmap_min_addr). This handle cases in which mmap_min_addr >
PAGE_SIZE.

Fixes: fba2369e ("mm: use vm_unmapped_area() on powerpc architecture")
Reviewed-by: NLaurent Dufour <ldufour@linux.vnet.ibm.com>
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This patch fixes the following warnings (obtained with make W=1).

arch/powerpc/mm/slice.c: In function 'slice_range_to_mask':
arch/powerpc/mm/slice.c:73:12: error: comparison is always true due to limited range of data type [-Werror=type-limits]
  if (start < SLICE_LOW_TOP) {
            ^
arch/powerpc/mm/slice.c:81:20: error: comparison is always false due to limited range of data type [-Werror=type-limits]
  if ((start + len) > SLICE_LOW_TOP) {
                    ^
arch/powerpc/mm/slice.c: In function 'slice_mask_for_free':
arch/powerpc/mm/slice.c:136:17: error: comparison is always true due to limited range of data type [-Werror=type-limits]
  if (high_limit <= SLICE_LOW_TOP)
                 ^
arch/powerpc/mm/slice.c: In function 'slice_check_range_fits':
arch/powerpc/mm/slice.c:185:12: error: comparison is always true due to limited range of data type [-Werror=type-limits]
  if (start < SLICE_LOW_TOP) {
            ^
arch/powerpc/mm/slice.c:195:39: error: comparison is always false due to limited range of data type [-Werror=type-limits]
  if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
                                       ^
arch/powerpc/mm/slice.c: In function 'slice_scan_available':
arch/powerpc/mm/slice.c:306:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
  if (addr < SLICE_LOW_TOP) {
           ^
arch/powerpc/mm/slice.c: In function 'get_slice_psize':
arch/powerpc/mm/slice.c:709:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
  if (addr < SLICE_LOW_TOP) {
           ^
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This patch fixes the following warnings (obtained with make W=1).

arch/powerpc/mm/slice.c: At top level:
arch/powerpc/mm/slice.c:682:15: error: no previous prototype for 'arch_get_unmapped_area' [-Werror=missing-prototypes]
 unsigned long arch_get_unmapped_area(struct file *filp,
               ^
arch/powerpc/mm/slice.c:692:15: error: no previous prototype for 'arch_get_unmapped_area_topdown' [-Werror=missing-prototypes]
 unsigned long arch_get_unmapped_area_topdown(struct file *filp,
               ^
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

slb_flush_and_rebolt() is misleading, it is called in virtual mode, so
it can not possibly change the stack, so it should not be touching the
shadow area. And since vmalloc is no longer bolted, it should not
change any bolted mappings at all.

Change the name to slb_flush_and_restore_bolted(), and have it just
load the kernel stack from what's currently in the shadow SLB area.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This will be used by the SLB code in the next patch, but for now this
sets the slb_addr_limit to the correct size for 32-bit tasks.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This reverts commits:
  5e46e29e ("powerpc/64s/hash: convert SLB miss handlers to C")
  8fed04d0 ("powerpc/64s/hash: remove user SLB data from the paca")
  655deecf ("powerpc/64s/hash: SLB allocation status bitmaps")
  2e162674 ("powerpc/64s/hash: provide arch_setup_exec hooks for hash slice setup")
  89ca4e12 ("powerpc/64s/hash: Add a SLB preload cache")

This series had a few bugs, and the fixes are not all trivial. So
revert most of it for now.
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This will be used by the SLB code in the next patch, but for now this
sets the slb_addr_limit to the correct size for 32-bit tasks.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

User SLB mappig data is copied into the PACA from the mm->context so
it can be accessed by the SLB miss handlers.

After the C conversion, SLB miss handlers now run with relocation on,
and user SLB misses are able to take recursive kernel SLB misses, so
the user SLB mapping data can be removed from the paca and accessed
directly.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

8xx uses the slice code when hugetlbfs is enabled. We missed a header
include on 8xx which resulted in the below build failure:

  config: mpc885_ads_defconfig + CONFIG_HUGETLBFS

  arch/powerpc/mm/slice.c: In function 'slice_get_unmapped_area':
  arch/powerpc/mm/slice.c:655:2: error: implicit declaration of function 'need_extra_context'
  arch/powerpc/mm/slice.c:656:3: error: implicit declaration of function 'alloc_extended_context'

on PPC64 the mmu_context.h was included via linux/pkeys.h
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

For addresses above 512TB we allocate additional mmu contexts. To make
it all easy, addresses above 512TB are handled with IR/DR=1 and with
stack frame setup.

The mmu_context_t is also updated to track the new extended_ids. To
support upto 4PB we need a total 8 contexts.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Minor formatting tweaks and comment wording, switch BUG to WARN
      in get_ea_context().]
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

In a following patch, on finding a free area we will need to do
allocatinon of extra contexts as needed. Consolidating the return path
for slice_get_unmapped_area() will make that easier.

Split into a separate patch to make review easy.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This is a tidy up which removes radix MMU calls into the slice
code.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

The slice_mask cache was a basic conversion which copied the slice
mask into caller's structures, because that's how the original code
worked. In most cases the pointer can be used directly instead, saving
a copy and an on-stack structure.

On POWER8, this increases vfork+exec+exit performance by 0.3%
and reduces time to mmap+munmap a 64kB page by 2%.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This code is never compiled in, and it gets broken by the next
patch, so remove it.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This converts the slice_mask bit operation helpers to be the usual
3-operand kind, which allows 2 inputs to set a different output
without an extra copy, which is used in the next patch.

Adds slice_copy_mask, which will be used in the next patch.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Rather than build slice masks from a range then use that to check for
fit in a candidate mask, implement slice_check_range_fits that checks
if a range fits in a mask directly.

This allows several structures to be removed from stacks, and also we
don't expect a huge range in a lot of these cases, so building and
comparing a full mask is going to be more expensive than testing just
one or two bits of the range.

On POWER8, this increases vfork+exec+exit performance by 0.3%
and reduces time to mmap+munmap a 64kB page by 5%.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Calculating the slice mask can become a signifcant overhead for
get_unmapped_area. This patch adds a struct slice_mask for
each page size in the mm_context, and keeps these in synch with
the slices psize arrays and slb_addr_limit.

On Book3S/64 this adds 288 bytes to the mm_context_t for the
slice mask caches.

On POWER8, this increases vfork+exec+exit performance by 9.9%
and reduces time to mmap+munmap a 64kB page by 28%.

Reduces time to mmap+munmap by about 10% on 8xx.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Pass around const pointers to struct slice_mask where possible, rather
than copies of slice_mask, to reduce stack and call overhead.

checkstack.pl gives, before:
0x00000d1c slice_get_unmapped_area [slice.o]:		592
0x00001864 is_hugepage_only_range [slice.o]:		448
0x00000754 slice_find_area_topdown [slice.o]:		400
0x00000484 slice_find_area_bottomup.isra.1 [slice.o]:	272
0x000017b4 slice_set_range_psize [slice.o]:		224
0x00000a4c slice_find_area [slice.o]:			128
0x00000160 slice_check_fit [slice.o]:			112

after:
0x00000ad0 slice_get_unmapped_area [slice.o]:		448
0x00001464 is_hugepage_only_range [slice.o]:		288
0x000006c0 slice_find_area [slice.o]:			144
0x0000016c slice_check_fit [slice.o]:			128
0x00000528 slice_find_area_bottomup.isra.2 [slice.o]:	128
0x000013e4 slice_set_range_psize [slice.o]:		128

This increases vfork+exec+exit performance by 1.5%.

Reduces time to mmap+munmap a 64kB page by 17%.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Make these loops look the same, and change their form so the
important part is not wrapped over so many lines.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

The slice state of an mm gets zeroed then initialised upon exec.
This is the only caller of slice_set_user_psize now, so that can be
removed and instead implement a faster and simplified approach that
requires no locking or checking existing state.

This speeds up vfork+exec+exit performance on POWER8 by 3%.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

While the implementation of the "slices" address space allows
a significant amount of high slices, it limits the number of
low slices to 16 due to the use of a single u64 low_slices_psize
element in struct mm_context_t

On the 8xx, the minimum slice size is the size of the area
covered by a single PMD entry, ie 4M in 4K pages mode and 64M in
16K pages mode. This means we could have at least 64 slices.

In order to override this limitation, this patch switches the
handling of low_slices_psize to char array as done already for
high_slices_psize.
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

In preparation for the following patch which will fix an issue on
the 8xx by re-using the 'slices', this patch enhances the
'slices' implementation to support 32 bits CPUs.

On PPC32, the address space is limited to 4Gbytes, hence only the low
slices will be used.

The high slices use bitmaps. As bitmap functions are not prepared to
handle bitmaps of size 0, this patch ensures that bitmap functions
are called only when SLICE_NUM_HIGH is not nul.
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

bitmap_or() and bitmap_andnot() can work properly with dst identical
to src1 or src2. There is no need of an intermediate result bitmap
that is copied back to dst in a second step.
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

While computing slice mask for the free area we need make sure we only
search in the addr limit applicable for this mmap. We update the
slb_addr_limit after we request for a mmap above 128TB. But the
following mmap request with hint addr below 128TB should still limit
its search to below 128TB. ie. we should not use slb_addr_limit to
compute slice mask in this case. Instead, we should derive high addr
limit based on the mmap hint addr value.

Fixes: f4ea6dcb ("powerpc/mm: Enable mappings above 128TB")
Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Radix keeps no meaningful state in addr_limit, so remove it from radix
code and rename to slb_addr_limit to make it clear it applies to hash
only.
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

While mapping hints with a length that cross 128TB are disallowed,
MAP_FIXED allocations that cross 128TB are allowed. These are failing
on hash (on radix they succeed). Add an additional case for fixed
mappings to expand the addr_limit when crossing 128TB.

Fixes: f4ea6dcb ("powerpc/mm: Enable mappings above 128TB")
Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

When allocating VA space with a hint that crosses 128TB, the SLB
addr_limit variable is not expanded if addr is not > 128TB, but the
slice allocation looks at task_size, which is 512TB. This results in
slice_check_fit() incorrectly succeeding because the slice_count
truncates off bit 128 of the requested mask, so the comparison to the
available mask succeeds.

Fix this by using mm->context.addr_limit instead of mm->task_size for
testing allocation limits. This causes such allocations to fail.

Fixes: f4ea6dcb ("powerpc/mm: Enable mappings above 128TB")
Cc: stable@vger.kernel.org # v4.12+
Reported-by: NFlorian Weimer <fweimer@redhat.com>
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Currently userspace is able to request mmap() search between 128T-512T
by specifying a hint address that is greater than 128T. But that means
a hint of 128T exactly will return an address below 128T, which is
confusing and wrong.

So fix the logic to check the hint is greater than *or equal* to 128T.

Fixes: f4ea6dcb ("powerpc/mm: Enable mappings above 128TB")
Cc: stable@vger.kernel.org # v4.12+
Suggested-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Suggested-by: NNicholas Piggin <npiggin@gmail.com>
[mpe: Split out of Nick's bigger patch]
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.
Original-patch-by: NOleg Nesterov <oleg@redhat.com>
Original-patch-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NHugh Dickins <hughd@google.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

As part of the new large address space support, processes start out life with a
128TB virtual address space. However when calling mmap() a process can pass a
hint address, and if that hint is > 128TB the kernel will use the full 512TB
address space to try and satisfy the mmap() request.

Currently we have a check that the hint is > 128TB and < 512TB (TASK_SIZE),
which was added as an optimisation to avoid updating addr_limit unnecessarily
and also to avoid calling slice_flush_segments() on all CPUs more than
necessary.

However this has the user-visible side effect that an mmap() hint above 512TB
does not search the full address space unless a preceding mmap() used a hint
value > 128TB && < 512TB.

So fix it to treat any hint above 128TB as a hint to search the full address
space, instead of checking the hint against TASK_SIZE, we instead check if the
addr_limit is already == TASK_SIZE.

This also brings the ABI in-line with what is proposed on x86. ie, that a hint
address above 128TB up to and including (2^64)-1 is an indication to search the
full address space.

Fixes: f4ea6dcb (powerpc/mm: Enable mappings above 128TB)
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

We don't init addr_limit correctly for 32 bit applications. So default to using
mm->task_size for boundary condition checking. We use addr_limit to only control
free space search. This makes sure that we do the right thing with 32 bit
applications.

We should consolidate the usage of TASK_SIZE/mm->task_size and
mm->context.addr_limit later.

This partially reverts commit fbfef902 (powerpc/mm: Switch some
TASK_SIZE checks to use mm_context addr_limit).

Fixes: fbfef902 ("powerpc/mm: Switch some TASK_SIZE checks to use mm_context addr_limit")
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Not all user space application is ready to handle wide addresses. It's
known that at least some JIT compilers use higher bits in pointers to
encode their information. It collides with valid pointers with 512TB
addresses and leads to crashes.

To mitigate this, we are not going to allocate virtual address space
above 128TB by default.

But userspace can ask for allocation from full address space by
specifying hint address (with or without MAP_FIXED) above 128TB.

If hint address set above 128TB, but MAP_FIXED is not specified, we try
to look for unmapped area by specified address. If it's already
occupied, we look for unmapped area in *full* address space, rather than
from 128TB window.

This approach helps to easily make application's memory allocator aware
about large address space without manually tracking allocated virtual
address space.

This is going to be a per mmap decision. ie, we can have some mmaps with
larger addresses and other that do not.

A sample memory layout looks like:

  10000000-10010000 r-xp 00000000 fc:00 9057045          /home/max_addr_512TB
  10010000-10020000 r--p 00000000 fc:00 9057045          /home/max_addr_512TB
  10020000-10030000 rw-p 00010000 fc:00 9057045          /home/max_addr_512TB
  10029630000-10029660000 rw-p 00000000 00:00 0          [heap]
  7fff834a0000-7fff834b0000 rw-p 00000000 00:00 0
  7fff834b0000-7fff83670000 r-xp 00000000 fc:00 9177190  /lib/powerpc64le-linux-gnu/libc-2.23.so
  7fff83670000-7fff83680000 r--p 001b0000 fc:00 9177190  /lib/powerpc64le-linux-gnu/libc-2.23.so
  7fff83680000-7fff83690000 rw-p 001c0000 fc:00 9177190  /lib/powerpc64le-linux-gnu/libc-2.23.so
  7fff83690000-7fff836a0000 rw-p 00000000 00:00 0
  7fff836a0000-7fff836c0000 r-xp 00000000 00:00 0        [vdso]
  7fff836c0000-7fff83700000 r-xp 00000000 fc:00 9177193  /lib/powerpc64le-linux-gnu/ld-2.23.so
  7fff83700000-7fff83710000 r--p 00030000 fc:00 9177193  /lib/powerpc64le-linux-gnu/ld-2.23.so
  7fff83710000-7fff83720000 rw-p 00040000 fc:00 9177193  /lib/powerpc64le-linux-gnu/ld-2.23.so
  7fffdccf0000-7fffdcd20000 rw-p 00000000 00:00 0        [stack]
  1000000000000-1000000010000 rw-p 00000000 00:00 0
  1ffff83710000-1ffff83720000 rw-p 00000000 00:00 0
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

In the followup patch, we will increase the slice array size to handle
512TB range, but will limit the max addr to 128TB. Avoid doing
unnecessary computation and avoid doing slice mask related operation
above address limit.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

We now get output like below which is much better.

[    0.935306]  good_mask low_slice: 0-15
[    0.935360]  good_mask high_slice: 0-511

Compared to

[    0.953414]  good_mask:1111111111111111 - 1111111111111.........

I also fixed an error with slice_dbg printing.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This structure definition need not be in a header since this is used only by
slice.c file. So move it to slice.c. This also allow us to use SLICE_NUM_HIGH
instead of 64.

I also switch the low_slices type to u64 from u16. This doesn't have an impact
on size of struct due to padding added with u16 type. This helps in using
bitmap printing function for printing slice mask.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

We also update the function arg to struct mm_struct. Move this so that function
finds the definition of struct mm_struct. No functional change in this patch.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

This avoid copying the slice_mask struct as function return value
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

In followup patch we want to increase the va range which will result
in us requiring high_slices to have more than 64 bits. To enable this
convert high_slices to bitmap. We keep the number bits same in this patch
and later change that to higher value
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Fold in fix to use bitmap_empty()]
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>