<feed xmlns='http://www.w3.org/2005/Atom'>
<title>kernel/git/stable/linux.git/mm/page_alloc.c, branch linux-5.6.y</title>
<subtitle>Linux kernel stable tree</subtitle>
<id>https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/atom?h=linux-5.6.y</id>
<link rel='self' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/atom?h=linux-5.6.y'/>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/'/>
<updated>2020-05-14T05:59:24+00:00</updated>
<entry>
<title>mm: limit boost_watermark on small zones</title>
<updated>2020-05-14T05:59:24+00:00</updated>
<author>
<name>Henry Willard</name>
<email>henry.willard@oracle.com</email>
</author>
<published>2020-05-08T01:36:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9d588cbdeba1edceda1901b1f8593d749a6c46e7'/>
<id>urn:sha1:9d588cbdeba1edceda1901b1f8593d749a6c46e7</id>
<content type='text'>
commit 14f69140ff9c92a0928547ceefb153a842e8492c upstream.

Commit 1c30844d2dfe ("mm: reclaim small amounts of memory when an
external fragmentation event occurs") adds a boost_watermark() function
which increases the min watermark in a zone by at least
pageblock_nr_pages or the number of pages in a page block.

On Arm64, with 64K pages and 512M huge pages, this is 8192 pages or
512M.  It does this regardless of the number of managed pages managed in
the zone or the likelihood of success.

This can put the zone immediately under water in terms of allocating
pages from the zone, and can cause a small machine to fail immediately
due to OoM.  Unlike set_recommended_min_free_kbytes(), which
substantially increases min_free_kbytes and is tied to THP,
boost_watermark() can be called even if THP is not active.

The problem is most likely to appear on architectures such as Arm64
where pageblock_nr_pages is very large.

It is desirable to run the kdump capture kernel in as small a space as
possible to avoid wasting memory.  In some architectures, such as Arm64,
there are restrictions on where the capture kernel can run, and
therefore, the space available.  A capture kernel running in 768M can
fail due to OoM immediately after boost_watermark() sets the min in zone
DMA32, where most of the memory is, to 512M.  It fails even though there
is over 500M of free memory.  With boost_watermark() suppressed, the
capture kernel can run successfully in 448M.

This patch limits boost_watermark() to boosting a zone's min watermark
only when there are enough pages that the boost will produce positive
results.  In this case that is estimated to be four times as many pages
as pageblock_nr_pages.

Mel said:

: There is no harm in marking it stable.  Clearly it does not happen very
: often but it's not impossible.  32-bit x86 is a lot less common now
: which would previously have been vulnerable to triggering this easily.
: ppc64 has a larger base page size but typically only has one zone.
: arm64 is likely the most vulnerable, particularly when CMA is
: configured with a small movable zone.

Fixes: 1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs")
Signed-off-by: Henry Willard &lt;henry.willard@oracle.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Reviewed-by: David Hildenbrand &lt;david@redhat.com&gt;
Acked-by: Mel Gorman &lt;mgorman@techsingularity.net&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Link: http://lkml.kernel.org/r/1588294148-6586-1-git-send-email-henry.willard@oracle.com
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>mm/page_alloc: fix watchdog soft lockups during set_zone_contiguous()</title>
<updated>2020-05-14T05:59:24+00:00</updated>
<author>
<name>David Hildenbrand</name>
<email>david@redhat.com</email>
</author>
<published>2020-05-08T01:35:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=17a68145e058a80250515159bdf8d3a3a0adca65'/>
<id>urn:sha1:17a68145e058a80250515159bdf8d3a3a0adca65</id>
<content type='text'>
commit e84fe99b68ce353c37ceeecc95dce9696c976556 upstream.

Without CONFIG_PREEMPT, it can happen that we get soft lockups detected,
e.g., while booting up.

  watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1]
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.6.0-next-20200331+ #4
  Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
  RIP: __pageblock_pfn_to_page+0x134/0x1c0
  Call Trace:
   set_zone_contiguous+0x56/0x70
   page_alloc_init_late+0x166/0x176
   kernel_init_freeable+0xfa/0x255
   kernel_init+0xa/0x106
   ret_from_fork+0x35/0x40

The issue becomes visible when having a lot of memory (e.g., 4TB)
assigned to a single NUMA node - a system that can easily be created
using QEMU.  Inside VMs on a hypervisor with quite some memory
overcommit, this is fairly easy to trigger.

Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Reviewed-by: Pavel Tatashin &lt;pasha.tatashin@soleen.com&gt;
Reviewed-by: Pankaj Gupta &lt;pankaj.gupta.linux@gmail.com&gt;
Reviewed-by: Baoquan He &lt;bhe@redhat.com&gt;
Reviewed-by: Shile Zhang &lt;shile.zhang@linux.alibaba.com&gt;
Acked-by: Michal Hocko &lt;mhocko@suse.com&gt;
Cc: Kirill Tkhai &lt;ktkhai@virtuozzo.com&gt;
Cc: Shile Zhang &lt;shile.zhang@linux.alibaba.com&gt;
Cc: Pavel Tatashin &lt;pasha.tatashin@soleen.com&gt;
Cc: Daniel Jordan &lt;daniel.m.jordan@oracle.com&gt;
Cc: Michal Hocko &lt;mhocko@kernel.org&gt;
Cc: Alexander Duyck &lt;alexander.duyck@gmail.com&gt;
Cc: Baoquan He &lt;bhe@redhat.com&gt;
Cc: Oscar Salvador &lt;osalvador@suse.de&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Link: http://lkml.kernel.org/r/20200416073417.5003-1-david@redhat.com
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>mm/memmap_init: update variable name in memmap_init_zone</title>
<updated>2020-02-04T03:05:23+00:00</updated>
<author>
<name>Aneesh Kumar K.V</name>
<email>aneesh.kumar@linux.ibm.com</email>
</author>
<published>2020-02-04T01:34:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1f8d75c1b7dc62f017c542ca99e7da4a0839fb1e'/>
<id>urn:sha1:1f8d75c1b7dc62f017c542ca99e7da4a0839fb1e</id>
<content type='text'>
Patch series "mm/memory_hotplug: Shrink zones before removing memory", v6.

This series fixes the access of uninitialized memmaps when shrinking
zones/nodes and when removing memory.  Also, it contains all fixes for
crashes that can be triggered when removing certain namespace using
memunmap_pages() - ZONE_DEVICE, reported by Aneesh.

We stop trying to shrink ZONE_DEVICE, as it's buggy, fixing it would be
more involved (we don't have SECTION_IS_ONLINE as an indicator), and
shrinking is only of limited use (set_zone_contiguous() cannot detect the
ZONE_DEVICE as contiguous).

We continue shrinking !ZONE_DEVICE zones, however, I reduced the amount of
code to a minimum.  Shrinking is especially necessary to keep
zone-&gt;contiguous set where possible, especially, on memory unplug of DIMMs
at zone boundaries.

--------------------------------------------------------------------------

Zones are now properly shrunk when offlining memory blocks or when
onlining failed.  This allows to properly shrink zones on memory unplug
even if the separate memory blocks of a DIMM were onlined to different
zones or re-onlined to a different zone after offlining.

Example:

:/# cat /proc/zoneinfo
Node 1, zone  Movable
        spanned  0
        present  0
        managed  0
:/# echo "online_movable" &gt; /sys/devices/system/memory/memory41/state
:/# echo "online_movable" &gt; /sys/devices/system/memory/memory43/state
:/# cat /proc/zoneinfo
Node 1, zone  Movable
        spanned  98304
        present  65536
        managed  65536
:/# echo 0 &gt; /sys/devices/system/memory/memory43/online
:/# cat /proc/zoneinfo
Node 1, zone  Movable
        spanned  32768
        present  32768
        managed  32768
:/# echo 0 &gt; /sys/devices/system/memory/memory41/online
:/# cat /proc/zoneinfo
Node 1, zone  Movable
        spanned  0
        present  0
        managed  0

This patch (of 6):

The third argument is actually number of pages.  Change the variable name
from size to nr_pages to indicate this better.

No functional change in this patch.

Link: http://lkml.kernel.org/r/20191006085646.5768-3-david@redhat.com
Signed-off-by: Aneesh Kumar K.V &lt;aneesh.kumar@linux.ibm.com&gt;
Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Reviewed-by: Pankaj Gupta &lt;pagupta@redhat.com&gt;
Reviewed-by: David Hildenbrand &lt;david@redhat.com&gt;
Cc: Michal Hocko &lt;mhocko@suse.com&gt;
Cc: "Matthew Wilcox (Oracle)" &lt;willy@infradead.org&gt;
Cc: "Aneesh Kumar K.V" &lt;aneesh.kumar@linux.ibm.com&gt;
Cc: Pavel Tatashin &lt;pasha.tatashin@soleen.com&gt;
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: Logan Gunthorpe &lt;logang@deltatee.com&gt;
Cc: Oscar Salvador &lt;osalvador@suse.de&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm: factor out next_present_section_nr()</title>
<updated>2020-02-04T03:05:23+00:00</updated>
<author>
<name>David Hildenbrand</name>
<email>david@redhat.com</email>
</author>
<published>2020-02-04T01:34:02+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c6058814ec4460c25111e29452ef596acdcd61b'/>
<id>urn:sha1:4c6058814ec4460c25111e29452ef596acdcd61b</id>
<content type='text'>
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 (&gt;= all sane end_pfn).

Link: http://lkml.kernel.org/r/20200113144035.10848-3-david@redhat.com
Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Acked-by: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Cc: Baoquan He &lt;bhe@redhat.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: "Jin, Zhi" &lt;zhi.jin@intel.com&gt;
Cc: "Kirill A. Shutemov" &lt;kirill@shutemov.name&gt;
Cc: Mel Gorman &lt;mgorman@suse.de&gt;
Cc: Michal Hocko &lt;mhocko@kernel.org&gt;
Cc: Michal Hocko &lt;mhocko@suse.com&gt;
Cc: Oscar Salvador &lt;osalvador@suse.de&gt;
Cc: Pavel Tatashin &lt;pasha.tatashin@oracle.com&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/page_alloc: fix and rework pfn handling in memmap_init_zone()</title>
<updated>2020-02-04T03:05:23+00:00</updated>
<author>
<name>David Hildenbrand</name>
<email>david@redhat.com</email>
</author>
<published>2020-02-04T01:33:59+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=948c436e463d34e0d716aff0f333bb74471e5399'/>
<id>urn:sha1:948c436e463d34e0d716aff0f333bb74471e5399</id>
<content type='text'>
Let's update the pfn manually whenever we continue the loop.  This makes
the code easier to read but also less error prone (and we can directly fix
one issue).

When overlap_memmap_init() returns true, pfn is updated to
"memblock_region_memory_end_pfn(r)".  So it already points at the *next*
pfn to process.  Incrementing the pfn another time is wrong, we might
leave one uninitialized.  I spotted this by inspecting the code, so I have
no idea if this is relevant in practise (with kernelcore=mirror).

Link: http://lkml.kernel.org/r/20200113144035.10848-2-david@redhat.com
Fixes: a9a9e77fbf27 ("mm: move mirrored memory specific code outside of memmap_init_zone")
Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Acked-by: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Reviewed-by: Alexander Duyck &lt;alexander.h.duyck@linux.intel.com&gt;
Cc: Pavel Tatashin &lt;pasha.tatashin@oracle.com&gt;
Cc: Michal Hocko &lt;mhocko@kernel.org&gt;
Cc: Oscar Salvador &lt;osalvador@suse.de&gt;
Cc: Kirill A. Shutemov &lt;kirill@shutemov.name&gt;
Cc: Baoquan He &lt;bhe@redhat.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Cc: Mel Gorman &lt;mgorman@suse.de&gt;
Cc: "Jin, Zhi" &lt;zhi.jin@intel.com&gt;
Cc: Michal Hocko &lt;mhocko@suse.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/page_alloc.c: initialize memmap of unavailable memory directly</title>
<updated>2020-02-04T03:05:23+00:00</updated>
<author>
<name>David Hildenbrand</name>
<email>david@redhat.com</email>
</author>
<published>2020-02-04T01:33:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4b094b7851bf4bf551ad456195d3f26e1c03bd74'/>
<id>urn:sha1:4b094b7851bf4bf551ad456195d3f26e1c03bd74</id>
<content type='text'>
Let's make sure that all memory holes are actually marked PageReserved(),
that page_to_pfn() produces reliable results, and that these pages are not
detected as "mmap" pages due to the mapcount.

E.g., booting a x86-64 QEMU guest with 4160 MB:

[    0.010585] Early memory node ranges
[    0.010586]   node   0: [mem 0x0000000000001000-0x000000000009efff]
[    0.010588]   node   0: [mem 0x0000000000100000-0x00000000bffdefff]
[    0.010589]   node   0: [mem 0x0000000100000000-0x0000000143ffffff]

max_pfn is 0x144000.

Before this change:

[root@localhost ~]# ./page-types -r -a 0x144000,
             flags      page-count       MB  symbolic-flags                     long-symbolic-flags
0x0000000000000800           16384       64  ___________M_______________________________        mmap
             total           16384       64

After this change:

[root@localhost ~]# ./page-types -r -a 0x144000,
             flags      page-count       MB  symbolic-flags                     long-symbolic-flags
0x0000000100000000           16384       64  ___________________________r_______________        reserved
             total           16384       64

IOW, especially the unavailable physical memory ("memory hole") in the
last section would not get properly marked PageReserved() and is indicated
to be "mmap" memory.

Drop the trace of that function from include/linux/mm.h - nobody else
needs it, and rename it accordingly.

Note: The fake zone/node might not be covered by the zone/node span.  This
is not an urgent issue (for now, we had the same node/zone due to the
zeroing).  We'll need a clean way to mark memory holes (e.g., using a page
type PageHole() if possible or a fake ZONE_INVALID) and eventually stop
marking these memory holes PageReserved().

Link: http://lkml.kernel.org/r/20191211163201.17179-4-david@redhat.com
Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Cc: Oscar Salvador &lt;osalvador@suse.de&gt;
Cc: Michal Hocko &lt;mhocko@kernel.org&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: Alexey Dobriyan &lt;adobriyan@gmail.com&gt;
Cc: Bob Picco &lt;bob.picco@oracle.com&gt;
Cc: Daniel Jordan &lt;daniel.m.jordan@oracle.com&gt;
Cc: Michal Hocko &lt;mhocko@suse.com&gt;
Cc: Naoya Horiguchi &lt;n-horiguchi@ah.jp.nec.com&gt;
Cc: Pavel Tatashin &lt;pasha.tatashin@oracle.com&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Cc: Steven Sistare &lt;steven.sistare@oracle.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/page_alloc.c: fix uninitialized memmaps on a partially populated last section</title>
<updated>2020-02-04T03:05:23+00:00</updated>
<author>
<name>David Hildenbrand</name>
<email>david@redhat.com</email>
</author>
<published>2020-02-04T01:33:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e822969cab48b786b64246aad1a3ba2a774f5d23'/>
<id>urn:sha1:e822969cab48b786b64246aad1a3ba2a774f5d23</id>
<content type='text'>
Patch series "mm: fix max_pfn not falling on section boundary", v2.

Playing with different memory sizes for a x86-64 guest, I discovered that
some memmaps (highest section if max_mem does not fall on the section
boundary) are marked as being valid and online, but contain garbage.  We
have to properly initialize these memmaps.

Looking at /proc/kpageflags and friends, I found some more issues,
partially related to this.

This patch (of 3):

If max_pfn is not aligned to a section boundary, we can easily run into
BUGs.  This can e.g., be triggered on x86-64 under QEMU by specifying a
memory size that is not a multiple of 128MB (e.g., 4097MB, but also
4160MB).  I was told that on real HW, we can easily have this scenario
(esp., one of the main reasons sub-section hotadd of devmem was added).

The issue is, that we have a valid memmap (pfn_valid()) for the whole
section, and the whole section will be marked "online".
pfn_to_online_page() will succeed, but the memmap contains garbage.

E.g., doing a "./page-types -r -a 0x144001" when QEMU was started with "-m
4160M" - (see tools/vm/page-types.c):

[  200.476376] BUG: unable to handle page fault for address: fffffffffffffffe
[  200.477500] #PF: supervisor read access in kernel mode
[  200.478334] #PF: error_code(0x0000) - not-present page
[  200.479076] PGD 59614067 P4D 59614067 PUD 59616067 PMD 0
[  200.479557] Oops: 0000 [#4] SMP NOPTI
[  200.479875] CPU: 0 PID: 603 Comm: page-types Tainted: G      D W         5.5.0-rc1-next-20191209 #93
[  200.480646] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4
[  200.481648] RIP: 0010:stable_page_flags+0x4d/0x410
[  200.482061] Code: f3 ff 41 89 c0 48 b8 00 00 00 00 01 00 00 00 45 84 c0 0f 85 cd 02 00 00 48 8b 53 08 48 8b 2b 48f
[  200.483644] RSP: 0018:ffffb139401cbe60 EFLAGS: 00010202
[  200.484091] RAX: fffffffffffffffe RBX: fffffbeec5100040 RCX: 0000000000000000
[  200.484697] RDX: 0000000000000001 RSI: ffffffff9535c7cd RDI: 0000000000000246
[  200.485313] RBP: ffffffffffffffff R08: 0000000000000000 R09: 0000000000000000
[  200.485917] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000144001
[  200.486523] R13: 00007ffd6ba55f48 R14: 00007ffd6ba55f40 R15: ffffb139401cbf08
[  200.487130] FS:  00007f68df717580(0000) GS:ffff9ec77fa00000(0000) knlGS:0000000000000000
[  200.487804] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  200.488295] CR2: fffffffffffffffe CR3: 0000000135d48000 CR4: 00000000000006f0
[  200.488897] Call Trace:
[  200.489115]  kpageflags_read+0xe9/0x140
[  200.489447]  proc_reg_read+0x3c/0x60
[  200.489755]  vfs_read+0xc2/0x170
[  200.490037]  ksys_pread64+0x65/0xa0
[  200.490352]  do_syscall_64+0x5c/0xa0
[  200.490665]  entry_SYSCALL_64_after_hwframe+0x49/0xbe

But it can be triggered much easier via "cat /proc/kpageflags &gt; /dev/null"
after cold/hot plugging a DIMM to such a system:

[root@localhost ~]# cat /proc/kpageflags &gt; /dev/null
[  111.517275] BUG: unable to handle page fault for address: fffffffffffffffe
[  111.517907] #PF: supervisor read access in kernel mode
[  111.518333] #PF: error_code(0x0000) - not-present page
[  111.518771] PGD a240e067 P4D a240e067 PUD a2410067 PMD 0

This patch fixes that by at least zero-ing out that memmap (so e.g.,
page_to_pfn() will not crash).  Commit 907ec5fca3dc ("mm: zero remaining
unavailable struct pages") tried to fix a similar issue, but forgot to
consider this special case.

After this patch, there are still problems to solve.  E.g., not all of
these pages falling into a memory hole will actually get initialized later
and set PageReserved - they are only zeroed out - but at least the
immediate crashes are gone.  A follow-up patch will take care of this.

Link: http://lkml.kernel.org/r/20191211163201.17179-2-david@redhat.com
Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap")
Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Tested-by: Daniel Jordan &lt;daniel.m.jordan@oracle.com&gt;
Cc: Naoya Horiguchi &lt;n-horiguchi@ah.jp.nec.com&gt;
Cc: Pavel Tatashin &lt;pasha.tatashin@oracle.com&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Steven Sistare &lt;steven.sistare@oracle.com&gt;
Cc: Michal Hocko &lt;mhocko@suse.com&gt;
Cc: Daniel Jordan &lt;daniel.m.jordan@oracle.com&gt;
Cc: Bob Picco &lt;bob.picco@oracle.com&gt;
Cc: Oscar Salvador &lt;osalvador@suse.de&gt;
Cc: Alexey Dobriyan &lt;adobriyan@gmail.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: Michal Hocko &lt;mhocko@kernel.org&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Cc: &lt;stable@vger.kernel.org&gt;	[4.15+]
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/page_isolation: fix potential warning from user</title>
<updated>2020-01-31T18:30:39+00:00</updated>
<author>
<name>Qian Cai</name>
<email>cai@lca.pw</email>
</author>
<published>2020-01-31T06:15:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3d680bdf60a5bade3e8cbd049927e7f8b1d3fe97'/>
<id>urn:sha1:3d680bdf60a5bade3e8cbd049927e7f8b1d3fe97</id>
<content type='text'>
It makes sense to call the WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE)
from start_isolate_page_range(), but should avoid triggering it from
userspace, i.e, from is_mem_section_removable() because it could crash
the system by a non-root user if warn_on_panic is set.

While at it, simplify the code a bit by removing an unnecessary jump
label.

Link: http://lkml.kernel.org/r/20200120163915.1469-1-cai@lca.pw
Signed-off-by: Qian Cai &lt;cai@lca.pw&gt;
Suggested-by: Michal Hocko &lt;mhocko@kernel.org&gt;
Acked-by: Michal Hocko &lt;mhocko@suse.com&gt;
Reviewed-by: David Hildenbrand &lt;david@redhat.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/hotplug: silence a lockdep splat with printk()</title>
<updated>2020-01-31T18:30:39+00:00</updated>
<author>
<name>Qian Cai</name>
<email>cai@lca.pw</email>
</author>
<published>2020-01-31T06:14:57+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a55c0474a92d5c418bcbbe122368de0910aeac2'/>
<id>urn:sha1:4a55c0474a92d5c418bcbbe122368de0910aeac2</id>
<content type='text'>
It is not that hard to trigger lockdep splats by calling printk from
under zone-&gt;lock.  Most of them are false positives caused by lock
chains introduced early in the boot process and they do not cause any
real problems (although most of the early boot lock dependencies could
happen after boot as well).  There are some console drivers which do
allocate from the printk context as well and those should be fixed.  In
any case, false positives are not that trivial to workaround and it is
far from optimal to lose lockdep functionality for something that is a
non-issue.

So change has_unmovable_pages() so that it no longer calls dump_page()
itself - instead it returns a "struct page *" of the unmovable page back
to the caller so that in the case of a has_unmovable_pages() failure,
the caller can call dump_page() after releasing zone-&gt;lock.  Also, make
dump_page() is able to report a CMA page as well, so the reason string
from has_unmovable_pages() can be removed.

Even though has_unmovable_pages doesn't hold any reference to the
returned page this should be reasonably safe for the purpose of
reporting the page (dump_page) because it cannot be hotremoved in the
context of memory unplug.  The state of the page might change but that
is the case even with the existing code as zone-&gt;lock only plays role
for free pages.

While at it, remove a similar but unnecessary debug-only printk() as
well.  A sample of one of those lockdep splats is,

  WARNING: possible circular locking dependency detected
  ------------------------------------------------------
  test.sh/8653 is trying to acquire lock:
  ffffffff865a4460 (console_owner){-.-.}, at:
  console_unlock+0x207/0x750

  but task is already holding lock:
  ffff88883fff3c58 (&amp;(&amp;zone-&gt;lock)-&gt;rlock){-.-.}, at:
  __offline_isolated_pages+0x179/0x3e0

  which lock already depends on the new lock.

  the existing dependency chain (in reverse order) is:

  -&gt; #3 (&amp;(&amp;zone-&gt;lock)-&gt;rlock){-.-.}:
         __lock_acquire+0x5b3/0xb40
         lock_acquire+0x126/0x280
         _raw_spin_lock+0x2f/0x40
         rmqueue_bulk.constprop.21+0xb6/0x1160
         get_page_from_freelist+0x898/0x22c0
         __alloc_pages_nodemask+0x2f3/0x1cd0
         alloc_pages_current+0x9c/0x110
         allocate_slab+0x4c6/0x19c0
         new_slab+0x46/0x70
         ___slab_alloc+0x58b/0x960
         __slab_alloc+0x43/0x70
         __kmalloc+0x3ad/0x4b0
         __tty_buffer_request_room+0x100/0x250
         tty_insert_flip_string_fixed_flag+0x67/0x110
         pty_write+0xa2/0xf0
         n_tty_write+0x36b/0x7b0
         tty_write+0x284/0x4c0
         __vfs_write+0x50/0xa0
         vfs_write+0x105/0x290
         redirected_tty_write+0x6a/0xc0
         do_iter_write+0x248/0x2a0
         vfs_writev+0x106/0x1e0
         do_writev+0xd4/0x180
         __x64_sys_writev+0x45/0x50
         do_syscall_64+0xcc/0x76c
         entry_SYSCALL_64_after_hwframe+0x49/0xbe

  -&gt; #2 (&amp;(&amp;port-&gt;lock)-&gt;rlock){-.-.}:
         __lock_acquire+0x5b3/0xb40
         lock_acquire+0x126/0x280
         _raw_spin_lock_irqsave+0x3a/0x50
         tty_port_tty_get+0x20/0x60
         tty_port_default_wakeup+0xf/0x30
         tty_port_tty_wakeup+0x39/0x40
         uart_write_wakeup+0x2a/0x40
         serial8250_tx_chars+0x22e/0x440
         serial8250_handle_irq.part.8+0x14a/0x170
         serial8250_default_handle_irq+0x5c/0x90
         serial8250_interrupt+0xa6/0x130
         __handle_irq_event_percpu+0x78/0x4f0
         handle_irq_event_percpu+0x70/0x100
         handle_irq_event+0x5a/0x8b
         handle_edge_irq+0x117/0x370
         do_IRQ+0x9e/0x1e0
         ret_from_intr+0x0/0x2a
         cpuidle_enter_state+0x156/0x8e0
         cpuidle_enter+0x41/0x70
         call_cpuidle+0x5e/0x90
         do_idle+0x333/0x370
         cpu_startup_entry+0x1d/0x1f
         start_secondary+0x290/0x330
         secondary_startup_64+0xb6/0xc0

  -&gt; #1 (&amp;port_lock_key){-.-.}:
         __lock_acquire+0x5b3/0xb40
         lock_acquire+0x126/0x280
         _raw_spin_lock_irqsave+0x3a/0x50
         serial8250_console_write+0x3e4/0x450
         univ8250_console_write+0x4b/0x60
         console_unlock+0x501/0x750
         vprintk_emit+0x10d/0x340
         vprintk_default+0x1f/0x30
         vprintk_func+0x44/0xd4
         printk+0x9f/0xc5

  -&gt; #0 (console_owner){-.-.}:
         check_prev_add+0x107/0xea0
         validate_chain+0x8fc/0x1200
         __lock_acquire+0x5b3/0xb40
         lock_acquire+0x126/0x280
         console_unlock+0x269/0x750
         vprintk_emit+0x10d/0x340
         vprintk_default+0x1f/0x30
         vprintk_func+0x44/0xd4
         printk+0x9f/0xc5
         __offline_isolated_pages.cold.52+0x2f/0x30a
         offline_isolated_pages_cb+0x17/0x30
         walk_system_ram_range+0xda/0x160
         __offline_pages+0x79c/0xa10
         offline_pages+0x11/0x20
         memory_subsys_offline+0x7e/0xc0
         device_offline+0xd5/0x110
         state_store+0xc6/0xe0
         dev_attr_store+0x3f/0x60
         sysfs_kf_write+0x89/0xb0
         kernfs_fop_write+0x188/0x240
         __vfs_write+0x50/0xa0
         vfs_write+0x105/0x290
         ksys_write+0xc6/0x160
         __x64_sys_write+0x43/0x50
         do_syscall_64+0xcc/0x76c
         entry_SYSCALL_64_after_hwframe+0x49/0xbe

  other info that might help us debug this:

  Chain exists of:
    console_owner --&gt; &amp;(&amp;port-&gt;lock)-&gt;rlock --&gt; &amp;(&amp;zone-&gt;lock)-&gt;rlock

   Possible unsafe locking scenario:

         CPU0                    CPU1
         ----                    ----
    lock(&amp;(&amp;zone-&gt;lock)-&gt;rlock);
                                 lock(&amp;(&amp;port-&gt;lock)-&gt;rlock);
                                 lock(&amp;(&amp;zone-&gt;lock)-&gt;rlock);
    lock(console_owner);

   *** DEADLOCK ***

  9 locks held by test.sh/8653:
   #0: ffff88839ba7d408 (sb_writers#4){.+.+}, at:
  vfs_write+0x25f/0x290
   #1: ffff888277618880 (&amp;of-&gt;mutex){+.+.}, at:
  kernfs_fop_write+0x128/0x240
   #2: ffff8898131fc218 (kn-&gt;count#115){.+.+}, at:
  kernfs_fop_write+0x138/0x240
   #3: ffffffff86962a80 (device_hotplug_lock){+.+.}, at:
  lock_device_hotplug_sysfs+0x16/0x50
   #4: ffff8884374f4990 (&amp;dev-&gt;mutex){....}, at:
  device_offline+0x70/0x110
   #5: ffffffff86515250 (cpu_hotplug_lock.rw_sem){++++}, at:
  __offline_pages+0xbf/0xa10
   #6: ffffffff867405f0 (mem_hotplug_lock.rw_sem){++++}, at:
  percpu_down_write+0x87/0x2f0
   #7: ffff88883fff3c58 (&amp;(&amp;zone-&gt;lock)-&gt;rlock){-.-.}, at:
  __offline_isolated_pages+0x179/0x3e0
   #8: ffffffff865a4920 (console_lock){+.+.}, at:
  vprintk_emit+0x100/0x340

  stack backtrace:
  Hardware name: HPE ProLiant DL560 Gen10/ProLiant DL560 Gen10,
  BIOS U34 05/21/2019
  Call Trace:
   dump_stack+0x86/0xca
   print_circular_bug.cold.31+0x243/0x26e
   check_noncircular+0x29e/0x2e0
   check_prev_add+0x107/0xea0
   validate_chain+0x8fc/0x1200
   __lock_acquire+0x5b3/0xb40
   lock_acquire+0x126/0x280
   console_unlock+0x269/0x750
   vprintk_emit+0x10d/0x340
   vprintk_default+0x1f/0x30
   vprintk_func+0x44/0xd4
   printk+0x9f/0xc5
   __offline_isolated_pages.cold.52+0x2f/0x30a
   offline_isolated_pages_cb+0x17/0x30
   walk_system_ram_range+0xda/0x160
   __offline_pages+0x79c/0xa10
   offline_pages+0x11/0x20
   memory_subsys_offline+0x7e/0xc0
   device_offline+0xd5/0x110
   state_store+0xc6/0xe0
   dev_attr_store+0x3f/0x60
   sysfs_kf_write+0x89/0xb0
   kernfs_fop_write+0x188/0x240
   __vfs_write+0x50/0xa0
   vfs_write+0x105/0x290
   ksys_write+0xc6/0x160
   __x64_sys_write+0x43/0x50
   do_syscall_64+0xcc/0x76c
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

Link: http://lkml.kernel.org/r/20200117181200.20299-1-cai@lca.pw
Signed-off-by: Qian Cai &lt;cai@lca.pw&gt;
Reviewed-by: David Hildenbrand &lt;david@redhat.com&gt;
Cc: Michal Hocko &lt;mhocko@kernel.org&gt;
Cc: Sergey Senozhatsky &lt;sergey.senozhatsky.work@gmail.com&gt;
Cc: Petr Mladek &lt;pmladek@suse.com&gt;
Cc: Steven Rostedt (VMware) &lt;rostedt@goodmis.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm: remove "count" parameter from has_unmovable_pages()</title>
<updated>2020-01-31T18:30:38+00:00</updated>
<author>
<name>David Hildenbrand</name>
<email>david@redhat.com</email>
</author>
<published>2020-01-31T06:14:04+00:00</published>
<link rel='alternate' type='text/html' href='https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe4c86c916d9151113372369f322e7436167e6f3'/>
<id>urn:sha1:fe4c86c916d9151113372369f322e7436167e6f3</id>
<content type='text'>
Now that the memory isolate notifier is gone, the parameter is always 0.
Drop it and cleanup has_unmovable_pages().

Link: http://lkml.kernel.org/r/20191114131911.11783-3-david@redhat.com
Signed-off-by: David Hildenbrand &lt;david@redhat.com&gt;
Acked-by: Michal Hocko &lt;mhocko@suse.com&gt;
Cc: Oscar Salvador &lt;osalvador@suse.de&gt;
Cc: Anshuman Khandual &lt;anshuman.khandual@arm.com&gt;
Cc: Qian Cai &lt;cai@lca.pw&gt;
Cc: Pingfan Liu &lt;kernelfans@gmail.com&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: Pavel Tatashin &lt;pasha.tatashin@soleen.com&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Cc: Mel Gorman &lt;mgorman@techsingularity.net&gt;
Cc: Mike Rapoport &lt;rppt@linux.vnet.ibm.com&gt;
Cc: Wei Yang &lt;richardw.yang@linux.intel.com&gt;
Cc: Alexander Duyck &lt;alexander.h.duyck@linux.intel.com&gt;
Cc: Alexander Potapenko &lt;glider@google.com&gt;
Cc: Arun KS &lt;arunks@codeaurora.org&gt;
Cc: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
</feed>
