linux-stable.git/mm/page_alloc.c, branch linux-4.5.y

mm: use phys_addr_t for reserve_bootmem_region() arguments

2016-06-08T01:18:50+00:00

commit 4b50bcc7eda4d3cc9e3f2a0aa60e590fedf728c5 upstream.

Since commit 92923ca3aace ("mm: meminit: only set page reserved in the
memblock region") the reserved bit is set on reserved memblock regions.
However start and end address are passed as unsigned long.  This is only
32bit on i386, so it can end up marking the wrong pages reserved for
ranges at 4GB and above.

This was observed on a 32bit Xen dom0 which was booted with initial
memory set to a value below 4G but allowing to balloon in memory
(dom0_mem=1024M for example).  This would define a reserved bootmem
region for the additional memory (for example on a 8GB system there was
a reverved region covering the 4GB-8GB range).  But since the addresses
were passed on as unsigned long, this was actually marking all pages
from 0 to 4GB as reserved.

Fixes: 92923ca3aacef63 ("mm: meminit: only set page reserved in the memblock region")
Link: http://lkml.kernel.org/r/1463491221-10573-1-git-send-email-stefan.bader@canonical.com
Signed-off-by: Stefan Bader 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: update min_free_kbytes from khugepaged after core initialization

2016-05-11T09:21:35+00:00

commit bc22af74f271ef76b2e6f72f3941f91f0da3f5f8 upstream.

Khugepaged attempts to raise min_free_kbytes if its set too low.
However, on boot khugepaged sets min_free_kbytes first from
subsys_initcall(), and then the mm 'core' over-rides min_free_kbytes
after from init_per_zone_wmark_min(), via a module_init() call.

Khugepaged used to use a late_initcall() to set min_free_kbytes (such
that it occurred after the core initialization), however this was
removed when the initialization of min_free_kbytes was integrated into
the starting of the khugepaged thread.

The fix here is simply to invoke the core initialization using a
core_initcall() instead of module_init(), such that the previous
initialization ordering is restored.  I didn't restore the
late_initcall() since start_stop_khugepaged() already sets
min_free_kbytes via set_recommended_min_free_kbytes().

This was noticed when we had a number of page allocation failures when
moving a workload to a kernel with this new initialization ordering.  On
an 8GB system this restores min_free_kbytes back to 67584 from 11365
when CONFIG_TRANSPARENT_HUGEPAGE=y is set and either
CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS=y or
CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y.

Fixes: 79553da293d3 ("thp: cleanup khugepaged startup")
Signed-off-by: Jason Baron 
Acked-by: Kirill A. Shutemov 
Acked-by: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/page_alloc: prevent merging between isolated and other pageblocks

2016-04-12T14:33:48+00:00

commit d9dddbf556674bf125ecd925b24e43a5cf2a568a upstream.

Hanjun Guo has reported that a CMA stress test causes broken accounting of
CMA and free pages:

> Before the test, I got:
> -bash-4.3# cat /proc/meminfo | grep Cma
> CmaTotal:         204800 kB
> CmaFree:          195044 kB
>
>
> After running the test:
> -bash-4.3# cat /proc/meminfo | grep Cma
> CmaTotal:         204800 kB
> CmaFree:         6602584 kB
>
> So the freed CMA memory is more than total..
>
> Also the the MemFree is more than mem total:
>
> -bash-4.3# cat /proc/meminfo
> MemTotal:       16342016 kB
> MemFree:        22367268 kB
> MemAvailable:   22370528 kB

Laura Abbott has confirmed the issue and suspected the freepage accounting
rewrite around 3.18/4.0 by Joonsoo Kim.  Joonsoo had a theory that this is
caused by unexpected merging between MIGRATE_ISOLATE and MIGRATE_CMA
pageblocks:

> CMA isolates MAX_ORDER aligned blocks, but, during the process,
> partialy isolated block exists. If MAX_ORDER is 11 and
> pageblock_order is 9, two pageblocks make up MAX_ORDER
> aligned block and I can think following scenario because pageblock
> (un)isolation would be done one by one.
>
> (each character means one pageblock. 'C', 'I' means MIGRATE_CMA,
> MIGRATE_ISOLATE, respectively.
>
> CC -> IC -> II (Isolation)
> II -> CI -> CC (Un-isolation)
>
> If some pages are freed at this intermediate state such as IC or CI,
> that page could be merged to the other page that is resident on
> different type of pageblock and it will cause wrong freepage count.

This was supposed to be prevented by CMA operating on MAX_ORDER blocks,
but since it doesn't hold the zone->lock between pageblocks, a race
window does exist.

It's also likely that unexpected merging can occur between
MIGRATE_ISOLATE and non-CMA pageblocks.  This should be prevented in
__free_one_page() since commit 3c605096d315 ("mm/page_alloc: restrict
max order of merging on isolated pageblock").  However, we only check
the migratetype of the pageblock where buddy merging has been initiated,
not the migratetype of the buddy pageblock (or group of pageblocks)
which can be MIGRATE_ISOLATE.

Joonsoo has suggested checking for buddy migratetype as part of
page_is_buddy(), but that would add extra checks in allocator hotpath
and bloat-o-meter has shown significant code bloat (the function is
inline).

This patch reduces the bloat at some expense of more complicated code.
The buddy-merging while-loop in __free_one_page() is initially bounded
to pageblock_border and without any migratetype checks.  The checks are
placed outside, bumping the max_order if merging is allowed, and
returning to the while-loop with a statement which can't be possibly
considered harmful.

This fixes the accounting bug and also removes the arguably weird state
in the original commit 3c605096d315 where buddies could be left
unmerged.

Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
Link: https://lkml.org/lkml/2016/3/2/280
Signed-off-by: Vlastimil Babka 
Reported-by: Hanjun Guo 
Tested-by: Hanjun Guo 
Acked-by: Joonsoo Kim 
Debugged-by: Laura Abbott 
Debugged-by: Joonsoo Kim 
Cc: Mel Gorman 
Cc: "Kirill A. Shutemov" 
Cc: Johannes Weiner 
Cc: Minchan Kim 
Cc: Yasuaki Ishimatsu 
Cc: Zhang Yanfei 
Cc: Michal Nazarewicz 
Cc: Naoya Horiguchi 
Cc: "Aneesh Kumar K.V" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm, hugetlb: don't require CMA for runtime gigantic pages

2016-02-06T02:10:40+00:00

Commit 944d9fec8d7a ("hugetlb: add support for gigantic page allocation
at runtime") has added the runtime gigantic page allocation via
alloc_contig_range(), making this support available only when CONFIG_CMA
is enabled.  Because it doesn't depend on MIGRATE_CMA pageblocks and the
associated infrastructure, it is possible with few simple adjustments to
require only CONFIG_MEMORY_ISOLATION instead of full CONFIG_CMA.

After this patch, alloc_contig_range() and related functions are
available and used for gigantic pages with just CONFIG_MEMORY_ISOLATION
enabled.  Note CONFIG_CMA selects CONFIG_MEMORY_ISOLATION.  This allows
supporting runtime gigantic pages without the CMA-specific checks in
page allocator fastpaths.

Signed-off-by: Vlastimil Babka 
Cc: Luiz Capitulino 
Cc: Kirill A. Shutemov 
Cc: Zhang Yanfei 
Cc: Yasuaki Ishimatsu 
Cc: Joonsoo Kim 
Cc: Naoya Horiguchi 
Cc: Mel Gorman 
Cc: Davidlohr Bueso 
Cc: Hillf Danton 
Cc: Mike Kravetz 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

thp: make split_queue per-node

2016-02-03T16:28:43+00:00

Andrea Arcangeli suggested to make split queue per-node to improve
scalability.  Let's do it.

Signed-off-by: Kirill A. Shutemov 
Suggested-by: Andrea Arcangeli 
Reviewed-by: Andrea Arcangeli 
Cc: Hugh Dickins 
Cc: Dave Hansen 
Cc: Mel Gorman 
Cc: Rik van Riel 
Cc: Vlastimil Babka 
Cc: "Aneesh Kumar K.V" 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Jerome Marchand 
Cc: Sasha Levin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/page_alloc.c: remove unused struct zone *z variable

2016-01-16T01:56:32+00:00

Remove unused struct zone *z variable which appeared in 86051ca5eaf5
("mm: fix usemap initialization").

Signed-off-by: Alexander Kuleshov 
Acked-by: Kirill A. Shutemov 
Acked-by: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

x86, mm: introduce vmem_altmap to augment vmemmap_populate()

2016-01-16T01:56:32+00:00

In support of providing struct page for large persistent memory
capacities, use struct vmem_altmap to change the default policy for
allocating memory for the memmap array.  The default vmemmap_populate()
allocates page table storage area from the page allocator.  Given
persistent memory capacities relative to DRAM it may not be feasible to
store the memmap in 'System Memory'.  Instead vmem_altmap represents
pre-allocated "device pages" to satisfy vmemmap_alloc_block_buf()
requests.

Signed-off-by: Dan Williams 
Reported-by: kbuild test robot 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: Dave Hansen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

thp: introduce deferred_split_huge_page()

2016-01-16T01:56:32+00:00

Currently we don't split huge page on partial unmap.  It's not an ideal
situation.  It can lead to memory overhead.

Furtunately, we can detect partial unmap on page_remove_rmap().  But we
cannot call split_huge_page() from there due to locking context.

It's also counterproductive to do directly from munmap() codepath: in
many cases we will hit this from exit(2) and splitting the huge page
just to free it up in small pages is not what we really want.

The patch introduce deferred_split_huge_page() which put the huge page
into queue for splitting.  The splitting itself will happen when we get
memory pressure via shrinker interface.  The page will be dropped from
list on freeing through compound page destructor.

Signed-off-by: Kirill A. Shutemov 
Tested-by: Sasha Levin 
Tested-by: Aneesh Kumar K.V 
Acked-by: Vlastimil Babka 
Acked-by: Jerome Marchand 
Cc: Andrea Arcangeli 
Cc: Hugh Dickins 
Cc: Dave Hansen 
Cc: Mel Gorman 
Cc: Rik van Riel 
Cc: Naoya Horiguchi 
Cc: Steve Capper 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Christoph Lameter 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: rework mapcount accounting to enable 4k mapping of THPs

2016-01-16T01:56:32+00:00

We're going to allow mapping of individual 4k pages of THP compound.  It
means we need to track mapcount on per small page basis.

Straight-forward approach is to use ->_mapcount in all subpages to track
how many time this subpage is mapped with PMDs or PTEs combined.  But
this is rather expensive: mapping or unmapping of a THP page with PMD
would require HPAGE_PMD_NR atomic operations instead of single we have
now.

The idea is to store separately how many times the page was mapped as
whole -- compound_mapcount.  This frees up ->_mapcount in subpages to
track PTE mapcount.

We use the same approach as with compound page destructor and compound
order to store compound_mapcount: use space in first tail page,
->mapping this time.

Any time we map/unmap whole compound page (THP or hugetlb) -- we
increment/decrement compound_mapcount.  When we map part of compound
page with PTE we operate on ->_mapcount of the subpage.

page_mapcount() counts both: PTE and PMD mappings of the page.

Basically, we have mapcount for a subpage spread over two counters.  It
makes tricky to detect when last mapcount for a page goes away.

We introduced PageDoubleMap() for this.  When we split THP PMD for the
first time and there's other PMD mapping left we offset up ->_mapcount
in all subpages by one and set PG_double_map on the compound page.
These additional references go away with last compound_mapcount.

This approach provides a way to detect when last mapcount goes away on
per small page basis without introducing new overhead for most common
cases.

[akpm@linux-foundation.org: fix typo in comment]
[mhocko@suse.com: ignore partial THP when moving task]
Signed-off-by: Kirill A. Shutemov 
Tested-by: Aneesh Kumar K.V 
Acked-by: Jerome Marchand 
Cc: Sasha Levin 
Cc: Aneesh Kumar K.V 
Cc: Jerome Marchand 
Cc: Vlastimil Babka 
Cc: Andrea Arcangeli 
Cc: Hugh Dickins 
Cc: Dave Hansen 
Cc: Mel Gorman 
Cc: Rik van Riel 
Cc: Naoya Horiguchi 
Cc: Steve Capper 
Cc: Johannes Weiner 
Cc: Christoph Lameter 
Cc: David Rientjes 
Signed-off-by: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: sanitize page->mapping for tail pages

2016-01-16T01:56:32+00:00

We don't define meaning of page->mapping for tail pages.  Currently it's
always NULL, which can be inconsistent with head page and potentially
lead to problems.

Let's poison the pointer to catch all illigal uses.

page_rmapping(), page_mapping() and page_anon_vma() are changed to look
on head page.

The only illegal use I've caught so far is __GPF_COMP pages from sound
subsystem, mapped with PTEs.  do_shared_fault() is changed to use
page_rmapping() instead of direct access to fault_page->mapping.

Signed-off-by: Kirill A. Shutemov 
Reviewed-by: Jérôme Glisse 
Cc: Andrea Arcangeli 
Cc: Hugh Dickins 
Cc: Dave Hansen 
Cc: Mel Gorman 
Cc: Rik van Riel 
Cc: Vlastimil Babka 
Cc: Christoph Lameter 
Cc: Naoya Horiguchi 
Cc: Steve Capper 
Cc: "Aneesh Kumar K.V" 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Jerome Marchand 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds