linux.git/mm/sparse.c, branch v5.6-rc2

mm: factor out next_present_section_nr()

2020-02-04T03:05:23+00:00

Let's move it to the header and use the shorter variant from
mm/page_alloc.c (the original one will also check
"__highest_present_section_nr + 1", which is not necessary).  While at
it, make the section_nr in next_pfn() const.

In next_pfn(), we now return section_nr_to_pfn(-1) instead of -1 once we
exceed __highest_present_section_nr, which doesn't make a difference in
the caller as it is big enough (>= all sane end_pfn).

Link: http://lkml.kernel.org/r/20200113144035.10848-3-david@redhat.com
Signed-off-by: David Hildenbrand 
Acked-by: Kirill A. Shutemov 
Cc: Baoquan He 
Cc: Dan Williams 
Cc: "Jin, Zhi" 
Cc: "Kirill A. Shutemov" 
Cc: Mel Gorman 
Cc: Michal Hocko 
Cc: Michal Hocko 
Cc: Oscar Salvador 
Cc: Pavel Tatashin 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/sparse.c: reset section's mem_map when fully deactivated

2020-01-31T18:30:36+00:00

After commit ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug"),
when a mem section is fully deactivated, section_mem_map still records
the section's start pfn, which is not used any more and will be
reassigned during re-addition.

In analogy with alloc/free pattern, it is better to clear all fields of
section_mem_map.

Beside this, it breaks the user space tool "makedumpfile" [1], which
makes assumption that a hot-removed section has mem_map as NULL, instead
of checking directly against SECTION_MARKED_PRESENT bit.  (makedumpfile
will be better to change the assumption, and need a patch)

The bug can be reproduced on IBM POWERVM by "drmgr -c mem -r -q 5" ,
trigger a crash, and save vmcore by makedumpfile

[1]: makedumpfile, commit e73016540293 ("[v1.6.7] Update version")

Link: http://lkml.kernel.org/r/1579487594-28889-1-git-send-email-kernelfans@gmail.com
Signed-off-by: Pingfan Liu 
Acked-by: Michal Hocko 
Acked-by: David Hildenbrand 
Cc: Dan Williams 
Cc: Oscar Salvador 
Cc: Baoquan He 
Cc: Qian Cai 
Cc: Kazuhito Hagio 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug: don't free usage map when removing a re-added early section

2020-01-14T02:19:01+00:00

When we remove an early section, we don't free the usage map, as the
usage maps of other sections are placed into the same page.  Once the
section is removed, it is no longer an early section (especially, the
memmap is freed).  When we re-add that section, the usage map is reused,
however, it is no longer an early section.  When removing that section
again, we try to kfree() a usage map that was allocated during early
boot - bad.

Let's check against PageReserved() to see if we are dealing with an
usage map that was allocated during boot.  We could also check against
!(PageSlab(usage_page) || PageCompound(usage_page)), but PageReserved() is
cleaner.

Can be triggered using memtrace under ppc64/powernv:

  $ mount -t debugfs none /sys/kernel/debug/
  $ echo 0x20000000 > /sys/kernel/debug/powerpc/memtrace/enable
  $ echo 0x20000000 > /sys/kernel/debug/powerpc/memtrace/enable
   ------------[ cut here ]------------
   kernel BUG at mm/slub.c:3969!
   Oops: Exception in kernel mode, sig: 5 [#1]
   LE PAGE_SIZE=3D64K MMU=3DHash SMP NR_CPUS=3D2048 NUMA PowerNV
   Modules linked in:
   CPU: 0 PID: 154 Comm: sh Not tainted 5.5.0-rc2-next-20191216-00005-g0be1dba7b7c0 #61
   NIP kfree+0x338/0x3b0
   LR section_deactivate+0x138/0x200
   Call Trace:
     section_deactivate+0x138/0x200
     __remove_pages+0x114/0x150
     arch_remove_memory+0x3c/0x160
     try_remove_memory+0x114/0x1a0
     __remove_memory+0x20/0x40
     memtrace_enable_set+0x254/0x850
     simple_attr_write+0x138/0x160
     full_proxy_write+0x8c/0x110
     __vfs_write+0x38/0x70
     vfs_write+0x11c/0x2a0
     ksys_write+0x84/0x140
     system_call+0x5c/0x68
   ---[ end trace 4b053cbd84e0db62 ]---

The first invocation will offline+remove memory blocks.  The second
invocation will first add+online them again, in order to offline+remove
them again (usually we are lucky and the exact same memory blocks will
get "reallocated").

Tested on powernv with boot memory: The usage map will not get freed.
Tested on x86-64 with DIMMs: The usage map will get freed.

Using Dynamic Memory under a Power DLAPR can trigger it easily.

Triggering removal (I assume after previously removed+re-added) of
memory from the HMC GUI can crash the kernel with the same call trace
and is fixed by this patch.

Link: http://lkml.kernel.org/r/20191217104637.5509-1-david@redhat.com
Fixes: 326e1b8f83a4 ("mm/sparsemem: introduce a SECTION_IS_EARLY flag")
Signed-off-by: David Hildenbrand 
Tested-by: Pingfan Liu 
Cc: Dan Williams 
Cc: Oscar Salvador 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: support memblock alloc on the exact node for sparse_buffer_init()

2019-12-01T20:59:08+00:00

sparse_buffer_init() use memblock_alloc_try_nid_raw() to allocate memory
for page management structure, if memory allocation fails from specified
node, it will fall back to allocate from other nodes.

Normally, the page management structure will not exceed 2% of the total
memory, but a large continuous block of allocation is needed.  In most
cases, memory allocation from the specified node will succeed, but a
node memory become highly fragmented will fail.  we expect to allocate
memory base section rather than by allocating a large block of memory
from other NUMA nodes

Add memblock_alloc_exact_nid_raw() for this situation, which allocate
boot memory block on the exact node.  If a large contiguous block memory
allocate fail in sparse_buffer_init(), it will fall back to allocate
small block memory base section.

Link: http://lkml.kernel.org/r/66755ea7-ab10-8882-36fd-3e02b03775d5@huawei.com
Signed-off-by: Yunfeng Ye 
Reviewed-by: Mike Rapoport 
Cc: Wei Yang 
Cc: Oscar Salvador 
Cc: Dan Williams 
Cc: David Hildenbrand 
Cc: Qian Cai 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/sparse.c: do not waste pre allocated memmap space

2019-12-01T20:59:05+00:00

Vincent has noticed [1] that there is something unusual with the memmap
allocations going on on his platform

: I noticed this because on my ARM64 platform, with 1 GiB of memory the
: first [and only] section is allocated from the zeroing path while with
: 2 GiB of memory the first 1 GiB section is allocated from the
: non-zeroing path.

The underlying problem is that although sparse_buffer_init allocates
enough memory for all sections on the node sparse_buffer_alloc is not
able to consume them due to mismatch in the expected allocation
alignement.  While sparse_buffer_init preallocation uses the PAGE_SIZE
alignment the real memmap has to be aligned to section_map_size() this
results in a wasted initial chunk of the preallocated memmap and
unnecessary fallback allocation for a section.

While we are at it also change __populate_section_memmap to align to the
requested size because at least VMEMMAP has constrains to have memmap
properly aligned.

[1] http://lkml.kernel.org/r/20191030131122.8256-1-vincent.whitchurch@axis.com

[akpm@linux-foundation.org: tweak layout, per David]
Link: http://lkml.kernel.org/r/20191119092642.31799-1-mhocko@kernel.org
Fixes: 35fd1eb1e821 ("mm/sparse: abstract sparse buffer allocations")
Signed-off-by: Michal Hocko 
Reported-by: Vincent Whitchurch 
Debugged-by: Vincent Whitchurch 
Acked-by: David Hildenbrand 
Cc: Pavel Tatashin 
Cc: Oscar Salvador 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/sparse.c: mark populate_section_memmap as __meminit

2019-12-01T20:59:05+00:00

Building the kernel on s390 with -Og produces the following warning:

  WARNING: vmlinux.o(.text+0x28dabe): Section mismatch in reference from the function populate_section_memmap() to the function .meminit.text:__populate_section_memmap()
  The function populate_section_memmap() references
  the function __meminit __populate_section_memmap().
  This is often because populate_section_memmap lacks a __meminit
  annotation or the annotation of __populate_section_memmap is wrong.

While -Og is not supported, in theory this might still happen with
another compiler or on another architecture.  So fix this by using the
correct section annotations.

[iii@linux.ibm.com: v2]
  Link: http://lkml.kernel.org/r/20191030151639.41486-1-iii@linux.ibm.com
Link: http://lkml.kernel.org/r/20191028165549.14478-1-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich 
Acked-by: David Hildenbrand 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Oscar Salvador 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/sparse: consistently do not zero memmap

2019-12-01T20:59:05+00:00

sparsemem without VMEMMAP has two allocation paths to allocate the
memory needed for its memmap (done in sparse_mem_map_populate()).

In one allocation path (sparse_buffer_alloc() succeeds), the memory is
not zeroed (since it was previously allocated with
memblock_alloc_try_nid_raw()).

In the other allocation path (sparse_buffer_alloc() fails and
sparse_mem_map_populate() falls back to memblock_alloc_try_nid()), the
memory is zeroed.

AFAICS this difference does not appear to be on purpose.  If the code is
supposed to work with non-initialized memory (__init_single_page() takes
care of zeroing the struct pages which are actually used), we should
consistently not zero the memory, to avoid masking bugs.

( I noticed this because on my ARM64 platform, with 1 GiB of memory the
  first [and only] section is allocated from the zeroing path while with
  2 GiB of memory the first 1 GiB section is allocated from the
  non-zeroing path. )

Michal:
 "the main user visible problem is a memory wastage. The overal amount
  of memory should be small. I wouldn't call it stable material."

Link: http://lkml.kernel.org/r/20191030131122.8256-1-vincent.whitchurch@axis.com
Signed-off-by: Vincent Whitchurch 
Acked-by: Michal Hocko 
Acked-by: David Hildenbrand 
Reviewed-by: Oscar Salvador 
Reviewed-by: Pavel Tatashin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: fix -Wmissing-prototypes warnings

2019-10-07T22:47:19+00:00

We get two warnings when build kernel W=1:

  mm/shuffle.c:36:12: warning: no previous prototype for `shuffle_show' [-Wmissing-prototypes]
  mm/sparse.c:220:6: warning: no previous prototype for `subsection_mask_set' [-Wmissing-prototypes]

Make the functions static to fix this.

Link: http://lkml.kernel.org/r/1566978161-7293-1-git-send-email-wang.yi59@zte.com.cn
Signed-off-by: Yi Wang 
Reviewed-by: David Hildenbrand 
Reviewed-by: Kees Cook 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/sparse.c: remove NULL check in clear_hwpoisoned_pages()

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

There is no possibility for memmap to be NULL in the current codebase.

This check was added in commit 95a4774d055c ("memory-hotplug: update
mce_bad_pages when removing the memory") where memmap was originally
inited to NULL, and only conditionally given a value.

The code that could have passed a NULL has been removed by commit
ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug"), so there is no
longer a possibility that memmap can be NULL.

Link: http://lkml.kernel.org/r/20190829035151.20975-1-alastair@d-silva.org
Signed-off-by: Alastair D'Silva 
Acked-by: Michal Hocko 
Reviewed-by: David Hildenbrand 
Cc: Mike Rapoport 
Cc: Wei Yang 
Cc: Qian Cai 
Cc: Alexander Duyck 
Cc: Logan Gunthorpe 
Cc: Baoquan He 
Cc: Balbir Singh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/sparse.c: don't manually decrement num_poisoned_pages

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

Use the function written to do it instead.

Link: http://lkml.kernel.org/r/20190827053656.32191-2-alastair@au1.ibm.com
Signed-off-by: Alastair D'Silva 
Acked-by: Michal Hocko 
Reviewed-by: David Hildenbrand 
Acked-by: Mike Rapoport 
Reviewed-by: Wei Yang 
Reviewed-by: Oscar Salvador 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds