Mark memcg1_events static: it's only used by memcontrol.c.  And mark it
const: it's not modified.

Link: http://lkml.kernel.org/r/20180503192940.94971-1-gthelen@google.comSigned-off-by: NGreg Thelen <gthelen@google.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mem_cgroup_cgwb_list is a very simple wrapper and it will never be used
outside of code under CONFIG_CGROUP_WRITEBACK.  so use memcg->cgwb_list
directly.

Link: http://lkml.kernel.org/r/1524406173-212182-1-git-send-email-wanglong19@meituan.comSigned-off-by: NWang Long <wanglong19@meituan.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Acked-by: NTejun Heo <tj@kernel.org>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

tmpfs uses the helper d_find_alias() to find a dentry from a decoded
inode, but d_find_alias() skips unhashed dentries, so unlinked files
cannot be decoded from a file handle.

This can be reproduced using xfstests test program open_by_handle:

  $ open_by handle -c /tmp/testdir
  $ open_by_handle -dk /tmp/testdir
  open_by_handle(/tmp/testdir/file000000) returned 116 incorrectly on an unlinked open file!

To fix this, if d_find_alias() can't find a hashed alias, call
d_find_any_alias() to return an unhashed one.

Link: http://lkml.kernel.org/r/CAOQ4uxg+qSLP0KwdW+h1tcPqOCQd+_pGZVXiePQB1TXCMBMctQ@mail.gmail.comSigned-off-by: NAmir Goldstein <amir73il@gmail.com>
Reviewed-by: NNeilBrown <neilb@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

page_stable_node() and set_page_stable_node() are only used in mm/ksm.c
and there is no point to keep them in the include/linux/ksm.h

[akpm@linux-foundation.org: fix SYSFS=n build]
Link: http://lkml.kernel.org/r/1524552106-7356-3-git-send-email-rppt@linux.vnet.ibm.comSigned-off-by: NMike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

While revisiting my Btrfs swapfile series [1], I introduced a situation
in which reclaim would lock i_rwsem, and even though the swapon() path
clearly made GFP_KERNEL allocations while holding i_rwsem, I got no
complaints from lockdep.  It turns out that the rework of the fs_reclaim
annotation was broken: if the current task has PF_MEMALLOC set, we don't
acquire the dummy fs_reclaim lock, but when reclaiming we always check
this _after_ we've just set the PF_MEMALLOC flag.  In most cases, we can
fix this by moving the fs_reclaim_{acquire,release}() outside of the
memalloc_noreclaim_{save,restore}(), althought kswapd is slightly
different.  After applying this, I got the expected lockdep splats.

1: https://lwn.net/Articles/625412/

Link: http://lkml.kernel.org/r/9f8aa70652a98e98d7c4de0fc96a4addcee13efe.1523778026.git.osandov@fb.com
Fixes: d92a8cfc ("locking/lockdep: Rework FS_RECLAIM annotation")
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since tmpfs THP was supported in 4.8, hugetlbfs is not the only
filesystem with huge page support anymore.  tmpfs can use huge page via
THP when mounting by "huge=" mount option.

When applications use huge page on hugetlbfs, it just need check the
filesystem magic number, but it is not enough for tmpfs.  Make
stat.st_blksize return huge page size if it is mounted by appropriate
"huge=" option to give applications a hint to optimize the behavior with
THP.

Some applications may not do wisely with THP.  For example, QEMU may
mmap file on non huge page aligned hint address with MAP_FIXED, which
results in no pages are PMD mapped even though THP is used.  Some
applications may mmap file with non huge page aligned offset.  Both
behaviors make THP pointless.

statfs.f_bsize still returns 4KB for tmpfs since THP could be split, and
it also may fallback to 4KB page silently if there is not enough huge
page.  Furthermore, different f_bsize makes max_blocks and free_blocks
calculation harder but without too much benefit.  Returning huge page
size via stat.st_blksize sounds good enough.

Since PUD size huge page for THP has not been supported, now it just
returns HPAGE_PMD_SIZE.

Hugh said:

: Sorry, I have no enthusiasm for this patch; but do I feel strongly
: enough to override you and everyone else to NAK it?  No, I don't feel
: that strongly, maybe st_blksize isn't worth arguing over.
:
: We did look at struct stat when designing huge tmpfs, to see if there
: were any fields that should be adjusted for it; but concluded none.
: Yes, it would sometimes be nice to have a quickly accessible indicator
: for when tmpfs has been mounted huge (scanning /proc/mounts for options
: can be tiresome, agreed); but since tmpfs tries to supply huge (or not)
: pages transparently, no difference seemed right.
:
: So, because st_blksize is a not very useful field of struct stat, with
: "size" in the name, we're going to put HPAGE_PMD_SIZE in there instead
: of PAGE_SIZE, if the tmpfs was mounted with one of the huge "huge"
: options (force or always, okay; within_size or advise, not so much).
: Though HPAGE_PMD_SIZE is no more its "preferred I/O size" or "blocksize
: for file system I/O" than PAGE_SIZE was.
:
: Which we can expect to speed up some applications and disadvantage
: others, depending on how they interpret st_blksize: just like if we
: changed it in the same way on non-huge tmpfs.  (Did I actually try
: changing st_blksize early on, and find it broke something?  If so, I've
: now forgotten what, and a search through commit messages didn't find
: it; but I guess we'll find out soon enough.)
:
: If there were an mstat() syscall, returning a field "preferred
: alignment", then we could certainly agree to put HPAGE_PMD_SIZE in
: there; but in stat()'s st_blksize?  And what happens when (in future)
: mm maps this or that hard-disk filesystem's blocks with a pmd mapping -
: should that filesystem then advertise a bigger st_blksize, despite the
: same disk layout as before?  What happens with DAX?
:
: And this change is not going to help the QEMU suboptimality that
: brought you here (or does QEMU align mmaps according to st_blksize?).
: QEMU ought to work well with kernels without this change, and kernels
: with this change; and I hope it can easily deal with both by avoiding
: that use of MAP_FIXED which prevented the kernel's intended alignment.

[akpm@linux-foundation.org: remove unneeded `else']
Link: http://lkml.kernel.org/r/1524665633-83806-1-git-send-email-yang.shi@linux.alibaba.comSigned-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Suggested-by: NChristoph Hellwig <hch@infradead.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Client can call vunmap with some intermediate 'addr' which may not be
the start of the VM area.  Entire unmap code works with vm->vm_start
which is proper but debug object API is called with 'addr'.  This could
be a problem within debug objects.

Pass proper start address into debug object API.

[akpm@linux-foundation.org: fix warning]
Link: http://lkml.kernel.org/r/1523961828-9485-3-git-send-email-cpandya@codeaurora.orgSigned-off-by: NChintan Pandya <cpandya@codeaurora.org>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently, __vunmap flow is,
 1) Release the VM area
 2) Free the debug objects corresponding to that vm area.

This leave some race window open.
 1) Release the VM area
 1.5) Some other client gets the same vm area
 1.6) This client allocates new debug objects on the same
      vm area
 2) Free the debug objects corresponding to this vm area.

Here, we actually free 'other' client's debug objects.

Fix this by freeing the debug objects first and then releasing the VM
area.

Link: http://lkml.kernel.org/r/1523961828-9485-2-git-send-email-cpandya@codeaurora.orgSigned-off-by: NChintan Pandya <cpandya@codeaurora.org>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

vunmap does page table clear operations twice in the case when
DEBUG_PAGEALLOC_ENABLE_DEFAULT is enabled.

So, clean up the code as that is unintended.

As a perf gain, we save few us.  Below ftrace data was obtained while
doing 1 MB of vmalloc/vfree on ARM64 based SoC *without* this patch
applied.  After this patch, we can save ~3 us (on 1 extra
vunmap_page_range).

  CPU  DURATION                  FUNCTION CALLS
  |     |   |                     |   |   |   |
 6)               |  __vunmap() {
 6)               |    vmap_debug_free_range() {
 6)   3.281 us    |      vunmap_page_range();
 6) + 45.468 us   |    }
 6)   2.760 us    |    vunmap_page_range();
 6) ! 505.105 us  |  }

[cpandya@codeaurora.org: v3]
  Link: http://lkml.kernel.org/r/1525176960-18408-1-git-send-email-cpandya@codeaurora.org
Link: http://lkml.kernel.org/r/1523876342-10545-1-git-send-email-cpandya@codeaurora.orgSigned-off-by: NChintan Pandya <cpandya@codeaurora.org>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In commit c4e1be9e ("mm, sparsemem: break out of loops early")
__highest_present_section_nr is introduced to reduce the loop counts for
present section.  This is also helpful for usemap and memmap allocation.

This patch uses __highest_present_section_nr + 1 to optimize the loop.

Link: http://lkml.kernel.org/r/20180326081956.75275-1-richard.weiyang@gmail.comSigned-off-by: NWei Yang <richard.weiyang@gmail.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When searching a present section, there are two boundaries:

    * __highest_present_section_nr
    * NR_MEM_SECTIONS

And it is known, __highest_present_section_nr is a more strict boundary
than NR_MEM_SECTIONS.  This means it would be necessary to check
__highest_present_section_nr only.

Link: http://lkml.kernel.org/r/20180326081956.75275-2-richard.weiyang@gmail.comSigned-off-by: NWei Yang <richard.weiyang@gmail.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mmap_sem will be read locked when calling follow_pmd_mask().  But this
cannot prevent PMD from being changed for all cases when PTL is
unlocked, for example, from pmd_trans_huge() to pmd_none() via
MADV_DONTNEED.  So it is possible for the pmd_present() check in
follow_pmd_mask() to encounter an invalid PMD.  This may cause an
incorrect VM_BUG_ON() or an infinite loop.  Fix this by reading the PMD
entry into a local variable with READ_ONCE() and checking the local
variable and pmd_none() in the retry loop.

As Kirill pointed out, with PTL unlocked, the *pmd may be changed under
us, so reading it directly again and again may incur weird bugs.  So
although using *pmd directly other than for pmd_present() checking may
be safe, it is still better to replace them to read *pmd once and check
the local variable multiple times.

When PTL unlocked, replace all *pmd with local variable was suggested by
Kirill.

Link: http://lkml.kernel.org/r/20180419083514.1365-1-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com>
Reviewed-by: NZi Yan <zi.yan@cs.rutgers.edu>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If memcg's usage is equal to the memory.low value, avoid reclaiming from
this cgroup while there is a surplus of reclaimable memory.

This sounds more logical and also matches memory.high and memory.max
behavior: both are inclusive.

Empty cgroups are not considered protected, so MEMCG_LOW events are not
emitted for empty cgroups, if there is no more reclaimable memory in the
system.

Link: http://lkml.kernel.org/r/20180406122132.GA7185@castleSigned-off-by: NRoman Gushchin <guro@fb.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch aims to address an issue in current memory.low semantics,
which makes it hard to use it in a hierarchy, where some leaf memory
cgroups are more valuable than others.

For example, there are memcgs A, A/B, A/C, A/D and A/E:

  A      A/memory.low = 2G, A/memory.current = 6G
 //\\
BC  DE   B/memory.low = 3G  B/memory.current = 2G
         C/memory.low = 1G  C/memory.current = 2G
         D/memory.low = 0   D/memory.current = 2G
	 E/memory.low = 10G E/memory.current = 0

If we apply memory pressure, B, C and D are reclaimed at the same pace
while A's usage exceeds 2G.  This is obviously wrong, as B's usage is
fully below B's memory.low, and C has 1G of protection as well.  Also, A
is pushed to the size, which is less than A's 2G memory.low, which is
also wrong.

A simple bash script (provided below) can be used to reproduce
the problem. Current results are:
  A:    1430097920
  A/B:  711929856
  A/C:  717426688
  A/D:  741376
  A/E:  0

To address the issue a concept of effective memory.low is introduced.
Effective memory.low is always equal or less than original memory.low.
In a case, when there is no memory.low overcommittment (and also for
top-level cgroups), these two values are equal.

Otherwise it's a part of parent's effective memory.low, calculated as a
cgroup's memory.low usage divided by sum of sibling's memory.low usages
(under memory.low usage I mean the size of actually protected memory:
memory.current if memory.current < memory.low, 0 otherwise).  It's
necessary to track the actual usage, because otherwise an empty cgroup
with memory.low set (A/E in my example) will affect actual memory
distribution, which makes no sense.  To avoid traversing the cgroup tree
twice, page_counters code is reused.

Calculating effective memory.low can be done in the reclaim path, as we
conveniently traversing the cgroup tree from top to bottom and check
memory.low on each level.  So, it's a perfect place to calculate
effective memory low and save it to use it for children cgroups.

This also eliminates a need to traverse the cgroup tree from bottom to
top each time to check if parent's guarantee is not exceeded.

Setting/resetting effective memory.low is intentionally racy, but it's
fine and shouldn't lead to any significant differences in actual memory
distribution.

With this patch applied results are matching the expectations:
  A:    2147930112
  A/B:  1428721664
  A/C:  718393344
  A/D:  815104
  A/E:  0

Test script:
  #!/bin/bash

  CGPATH="/sys/fs/cgroup"

  truncate /file1 --size 2G
  truncate /file2 --size 2G
  truncate /file3 --size 2G
  truncate /file4 --size 50G

  mkdir "${CGPATH}/A"
  echo "+memory" > "${CGPATH}/A/cgroup.subtree_control"
  mkdir "${CGPATH}/A/B" "${CGPATH}/A/C" "${CGPATH}/A/D" "${CGPATH}/A/E"

  echo 2G > "${CGPATH}/A/memory.low"
  echo 3G > "${CGPATH}/A/B/memory.low"
  echo 1G > "${CGPATH}/A/C/memory.low"
  echo 0 > "${CGPATH}/A/D/memory.low"
  echo 10G > "${CGPATH}/A/E/memory.low"

  echo $$ > "${CGPATH}/A/B/cgroup.procs" && vmtouch -qt /file1
  echo $$ > "${CGPATH}/A/C/cgroup.procs" && vmtouch -qt /file2
  echo $$ > "${CGPATH}/A/D/cgroup.procs" && vmtouch -qt /file3
  echo $$ > "${CGPATH}/cgroup.procs" && vmtouch -qt /file4

  echo "A:   " `cat "${CGPATH}/A/memory.current"`
  echo "A/B: " `cat "${CGPATH}/A/B/memory.current"`
  echo "A/C: " `cat "${CGPATH}/A/C/memory.current"`
  echo "A/D: " `cat "${CGPATH}/A/D/memory.current"`
  echo "A/E: " `cat "${CGPATH}/A/E/memory.current"`

  rmdir "${CGPATH}/A/B" "${CGPATH}/A/C" "${CGPATH}/A/D" "${CGPATH}/A/E"
  rmdir "${CGPATH}/A"
  rm /file1 /file2 /file3 /file4

Link: http://lkml.kernel.org/r/20180405185921.4942-2-guro@fb.comSigned-off-by: NRoman Gushchin <guro@fb.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch renames struct page_counter fields:
  count -> usage
  limit -> max

and the corresponding functions:
  page_counter_limit() -> page_counter_set_max()
  mem_cgroup_get_limit() -> mem_cgroup_get_max()
  mem_cgroup_resize_limit() -> mem_cgroup_resize_max()
  memcg_update_kmem_limit() -> memcg_update_kmem_max()
  memcg_update_tcp_limit() -> memcg_update_tcp_max()

The idea behind this renaming is to have the direct matching
between memory cgroup knobs (low, high, max) and page_counters API.

This is pure renaming, this patch doesn't bring any functional change.

Link: http://lkml.kernel.org/r/20180405185921.4942-1-guro@fb.comSigned-off-by: NRoman Gushchin <guro@fb.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

So far code was using ULLONG_MAX and type casting to obtain a
phys_addr_t with all bits set.  The typecast is necessary to silence
compiler warnings on 32-bit platforms.

Use the simpler but still type safe approach "~(phys_addr_t)0" to create a
preprocessor define for all bits set.

Link: http://lkml.kernel.org/r/20180406213809.566-1-stefan@agner.chSigned-off-by: NStefan Agner <stefan@agner.ch>
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove the additional define HAVE_PTE_SPECIAL and rely directly on
CONFIG_ARCH_HAS_PTE_SPECIAL.

There is no functional change introduced by this patch

Link: http://lkml.kernel.org/r/1523533733-25437-1-git-send-email-ldufour@linux.vnet.ibm.comSigned-off-by: NLaurent Dufour <ldufour@linux.vnet.ibm.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Christophe LEROY <christophe.leroy@c-s.fr>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently the PTE special supports is turned on in per architecture
header files.  Most of the time, it is defined in
arch/*/include/asm/pgtable.h depending or not on some other per
architecture static definition.

This patch introduce a new configuration variable to manage this
directly in the Kconfig files.  It would later replace
__HAVE_ARCH_PTE_SPECIAL.

Here notes for some architecture where the definition of
__HAVE_ARCH_PTE_SPECIAL is not obvious:

arm
 __HAVE_ARCH_PTE_SPECIAL which is currently defined in
arch/arm/include/asm/pgtable-3level.h which is included by
arch/arm/include/asm/pgtable.h when CONFIG_ARM_LPAE is set.
So select ARCH_HAS_PTE_SPECIAL if ARM_LPAE.

powerpc
__HAVE_ARCH_PTE_SPECIAL is defined in 2 files:
 - arch/powerpc/include/asm/book3s/64/pgtable.h
 - arch/powerpc/include/asm/pte-common.h
The first one is included if (PPC_BOOK3S & PPC64) while the second is
included in all the other cases.
So select ARCH_HAS_PTE_SPECIAL all the time.

sparc:
__HAVE_ARCH_PTE_SPECIAL is defined if defined(__sparc__) &&
defined(__arch64__) which are defined through the compiler in
sparc/Makefile if !SPARC32 which I assume to be if SPARC64.
So select ARCH_HAS_PTE_SPECIAL if SPARC64

There is no functional change introduced by this patch.

Link: http://lkml.kernel.org/r/1523433816-14460-2-git-send-email-ldufour@linux.vnet.ibm.comSigned-off-by: NLaurent Dufour <ldufour@linux.vnet.ibm.com>
Suggested-by: NJerome Glisse <jglisse@redhat.com>
Reviewed-by: NJerome Glisse <jglisse@redhat.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Albert Ou <albert@sifive.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Christophe LEROY <christophe.leroy@c-s.fr>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Highmem's realsize always equals to freesize, so it is not necessary to
spare a variable to record this.

Link: http://lkml.kernel.org/r/20180413083859.65888-1-richard.weiyang@gmail.comSigned-off-by: NWei Yang <richard.weiyang@gmail.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With the addition of memfd hugetlbfs support, we now have the situation
where memfd depends on TMPFS -or- HUGETLBFS.  Previously, memfd was only
supported on tmpfs, so it made sense that the code resided in shmem.c.
In the current code, memfd is only functional if TMPFS is defined.  If
HUGETLFS is defined and TMPFS is not defined, then memfd functionality
will not be available for hugetlbfs.  This does not cause BUGs, just a
lack of potentially desired functionality.

Code is restructured in the following way:
- include/linux/memfd.h is a new file containing memfd specific
  definitions previously contained in shmem_fs.h.
- mm/memfd.c is a new file containing memfd specific code previously
  contained in shmem.c.
- memfd specific code is removed from shmem_fs.h and shmem.c.
- A new config option MEMFD_CREATE is added that is defined if TMPFS
  or HUGETLBFS is defined.

No functional changes are made to the code: restructuring only.

Link: http://lkml.kernel.org/r/20180415182119.4517-4-mike.kravetz@oracle.comSigned-off-by: NMike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: NKhalid Aziz <khalid.aziz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marc-Andr Lureau <marcandre.lureau@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In preparation for memfd code restructure, update comments, definitions
and function names dealing with file sealing to indicate that tmpfs and
hugetlbfs are the supported filesystems.  Also, change file pointer
checks in memfd_file_seals_ptr to use defined interfaces instead of
directly referencing file_operation structs.

Link: http://lkml.kernel.org/r/20180415182119.4517-3-mike.kravetz@oracle.comSigned-off-by: NMike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: NKhalid Aziz <khalid.aziz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marc-Andr Lureau <marcandre.lureau@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "restructure memfd code", v4.

This patch (of 3):

In preparation for memfd code restucture, clean up sparse warnings.
Most changes required adding __rcu annotations.  The routine
find_swap_entry was modified to properly deference radix tree entries.

Link: http://lkml.kernel.org/r/20180415182119.4517-2-mike.kravetz@oracle.comSigned-off-by: NMike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: NMatthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Marc-Andr Lureau <marcandre.lureau@gmail.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add swap max and fail events so that userland can monitor and respond to
running out of swap.

I'm not too sure about the fail event.  Right now, it's a bit confusing
which stats / events are recursive and which aren't and also which ones
reflect events which originate from a given cgroup and which targets the
cgroup.  No idea what the right long term solution is and it could just
be that growing them organically is actually the only right thing to do.

Link: http://lkml.kernel.org/r/20180416231151.GI1911913@devbig577.frc2.facebook.comSigned-off-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "mm, memcontrol: Implement memory.swap.events", v2.

This patchset implements memory.swap.events which contains max and fail
events so that userland can monitor and respond to swap running out.

This patch (of 2):

get_swap_page() is always followed by mem_cgroup_try_charge_swap().
This patch moves mem_cgroup_try_charge_swap() into get_swap_page() and
makes get_swap_page() call the function even after swap allocation
failure.

This simplifies the callers and consolidates memcg related logic and
will ease adding swap related memcg events.

Link: http://lkml.kernel.org/r/20180416230934.GH1911913@devbig577.frc2.facebook.comSigned-off-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mmap_sem is on the hot path of kernel, and it very contended, but it is
abused too.  It is used to protect arg_start|end and evn_start|end when
reading /proc/$PID/cmdline and /proc/$PID/environ, but it doesn't make
sense since those proc files just expect to read 4 values atomically and
not related to VM, they could be set to arbitrary values by C/R.

And, the mmap_sem contention may cause unexpected issue like below:

INFO: task ps:14018 blocked for more than 120 seconds.
       Tainted: G            E 4.9.79-009.ali3000.alios7.x86_64 #1
 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
 ps              D    0 14018      1 0x00000004
 Call Trace:
   schedule+0x36/0x80
   rwsem_down_read_failed+0xf0/0x150
   call_rwsem_down_read_failed+0x18/0x30
   down_read+0x20/0x40
   proc_pid_cmdline_read+0xd9/0x4e0
   __vfs_read+0x37/0x150
   vfs_read+0x96/0x130
   SyS_read+0x55/0xc0
   entry_SYSCALL_64_fastpath+0x1a/0xc5

Both Alexey Dobriyan and Michal Hocko suggested to use dedicated lock
for them to mitigate the abuse of mmap_sem.

So, introduce a new spinlock in mm_struct to protect the concurrent
access to arg_start|end, env_start|end and others, as well as replace
write map_sem to read to protect the race condition between prctl and
sys_brk which might break check_data_rlimit(), and makes prctl more
friendly to other VM operations.

This patch just eliminates the abuse of mmap_sem, but it can't resolve
the above hung task warning completely since the later
access_remote_vm() call needs acquire mmap_sem.  The mmap_sem
scalability issue will be solved in the future.

[yang.shi@linux.alibaba.com: add comment about mmap_sem and arg_lock]
  Link: http://lkml.kernel.org/r/1524077799-80690-1-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1523730291-109696-1-git-send-email-yang.shi@linux.alibaba.comSigned-off-by: NYang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: NCyrill Gorcunov <gorcunov@openvz.org>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The obsolete comment removed in this patch was introduced by
51df1142 ("slub: Dynamically size kmalloc cache allocations").

I paste related modification from that commit:

+#ifdef CONFIG_NUMA
+       /*
+        * Allocate kmem_cache_node properly from the kmem_cache slab.
+        * kmem_cache_node is separately allocated so no need to
+        * update any list pointers.
+        */
+       temp_kmem_cache_node = kmem_cache_node;

+       kmem_cache_node = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);
+       memcpy(kmem_cache_node, temp_kmem_cache_node, kmem_size);
+
+       kmem_cache_bootstrap_fixup(kmem_cache_node);
+
+       caches++;
+#else
+       /*
+        * kmem_cache has kmem_cache_node embedded and we moved it!
+        * Update the list heads
+        */
+       INIT_LIST_HEAD(&kmem_cache->local_node.partial);
+       list_splice(&temp_kmem_cache->local_node.partial, &kmem_cache->local_node.partial);
+#ifdef CONFIG_SLUB_DEBUG
+       INIT_LIST_HEAD(&kmem_cache->local_node.full);
+       list_splice(&temp_kmem_cache->local_node.full, &kmem_cache->local_node.full);
+#endif

As we can see there're used to distinguish the difference handling
between NUMA/non-NUMA configuration in the original commit.  I think it
doesn't make any sense in current implementation which is placed above
kmem_cache_node = bootstrap(&boot_kmem_cache_node); So maybe it's better
to remove them now?

Link: http://lkml.kernel.org/r/5af26f58.1c69fb81.1be0e.c520SMTPIN_ADDED_BROKEN@mx.google.comSigned-off-by: NCanjiang Lu <canjiang.lu@samsung.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

__printf is useful to verify format and arguments.  Remove the following
warning (with W=1):

  mm/slub.c:721:2: warning: function might be possible candidate for `gnu_printf' format attribute [-Wsuggest-attribute=format]

Link: http://lkml.kernel.org/r/20180505200706.19986-1-malat@debian.orgSigned-off-by: NMathieu Malaterre <malat@debian.org>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

__GFP_ZERO requests that the object be initialised to all-zeroes, while
the purpose of a constructor is to initialise an object to a particular
pattern.  We cannot do both.  Add a warning to catch any users who
mistakenly pass a __GFP_ZERO flag when allocating a slab with a
constructor.

Link: http://lkml.kernel.org/r/20180412191322.GA21205@bombadil.infradead.org
Fixes: d07dbea4 ("Slab allocators: support __GFP_ZERO in all allocators")
Signed-off-by: NMatthew Wilcox <mawilcox@microsoft.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use new return type vm_fault_t for fault handler.  For now, this is just
documenting that the function returns a VM_FAULT value rather than an
errno.  Once all instances are converted, vm_fault_t will become a
distinct type.

commit 1c8f4220 ("mm: change return type to vm_fault_t")

There was an existing bug inside dax_load_hole() if vm_insert_mixed had
failed to allocate a page table, we'd return VM_FAULT_NOPAGE instead of
VM_FAULT_OOM.  With new vmf_insert_mixed() this issue is addressed.

vm_insert_mixed_mkwrite has inefficiency when it returns an error value,
driver has to convert it to vm_fault_t type.  With new
vmf_insert_mixed_mkwrite() this limitation will be addressed.

Link: http://lkml.kernel.org/r/20180510181121.GA15239@jordon-HP-15-Notebook-PCSigned-off-by: NSouptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NMatthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

George Boole would have noticed a slight error in 4.16 commit
69d763fc ("mm: pin address_space before dereferencing it while
isolating an LRU page").  Fix it, to match both the comment above it,
and the original behaviour.

Although anonymous pages are not marked PageDirty at first, we have an
old habit of calling SetPageDirty when a page is removed from swap
cache: so there's a category of ex-swap pages that are easily
migratable, but were inadvertently excluded from compaction's async
migration in 4.16.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1805302014001.12558@eggly.anvils
Fixes: 69d763fc ("mm: pin address_space before dereferencing it while isolating an LRU page")
Signed-off-by: NHugh Dickins <hughd@google.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@techsingularity.net>
Reported-by: NIvan Kalvachev <ikalvachev@gmail.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Swapping load on huge=always tmpfs (with khugepaged tuned up to be very
eager, but I'm not sure that is relevant) soon hung uninterruptibly,
waiting for page lock in shmem_getpage_gfp()'s find_lock_entry(), most
often when "cp -a" was trying to write to a smallish file.  Debug showed
that the page in question was not locked, and page->mapping NULL by now,
but page->index consistent with having been in a huge page before.

Reproduced in minutes on a 4.15 kernel, even with 4.17's 605ca5ed
("mm/huge_memory.c: reorder operations in __split_huge_page_tail()") added
in; but took hours to reproduce on a 4.17 kernel (no idea why).

The culprit proved to be the __ClearPageDirty() on tails beyond i_size in
__split_huge_page(): the non-atomic __bitoperation may have been safe when
4.8's baa355fd ("thp: file pages support for split_huge_page()")
introduced it, but liable to erase PageWaiters after 4.10's 62906027
("mm: add PageWaiters indicating tasks are waiting for a page bit").

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1805291841070.3197@eggly.anvils
Fixes: 62906027 ("mm: add PageWaiters indicating tasks are waiting for a page bit")
Signed-off-by: NHugh Dickins <hughd@google.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

That way file systems don't have to go spotting for non-contiguous pages
and work around them.  It also kicks off I/O earlier, allowing it to
finish earlier and reduce latency.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

We never return an error, so switch to returning an unsigned int.  Most
callers already did implicit casts to an unsigned type, and the one that
didn't can be simplified now.
Suggested-by: NMatthew Wilcox <willy@infradead.org>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

It counts the number of pages acted on, so name it nr_pages to make that
obvious.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

These abstract out calls to the poll method in preparation for changes
in how we poll.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

Using module_init() is wrong.  E.g.  ACPI adds and onlines memory before
our memory notifier gets registered.

This makes sure that ACPI memory detected during boot up will not result
in a kernel crash.

Easily reproducible with QEMU, just specify a DIMM when starting up.

Link: http://lkml.kernel.org/r/20180522100756.18478-3-david@redhat.com
Fixes: 786a8959 ("kasan: disable memory hotplug")
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Acked-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We have to free memory again when we cancel onlining, otherwise a later
onlining attempt will fail.

Link: http://lkml.kernel.org/r/20180522100756.18478-2-david@redhat.com
Fixes: fa69b598 ("mm/kasan: add support for memory hotplug")
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Acked-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The case of a new numa node got missed in avoiding using the node info
from page_struct during hotplug.  In this path we have a call to
register_mem_sect_under_node (which allows us to specify it is hotplug
so don't change the node), via link_mem_sections which unfortunately
does not.

Fix is to pass check_nid through link_mem_sections as well and disable
it in the new numa node path.

Note the bug only 'sometimes' manifests depending on what happens to be
in the struct page structures - there are lots of them and it only needs
to match one of them.

The result of the bug is that (with a new memory only node) we never
successfully call register_mem_sect_under_node so don't get the memory
associated with the node in sysfs and meminfo for the node doesn't
report it.

It came up whilst testing some arm64 hotplug patches, but appears to be
universal.  Whilst I'm triggering it by removing then reinserting memory
to a node with no other elements (thus making the node disappear then
appear again), it appears it would happen on hotplugging memory where
there was none before and it doesn't seem to be related the arm64
patches.

These patches call __add_pages (where most of the issue was fixed by
Pavel's patch).  If there is a node at the time of the __add_pages call
then all is well as it calls register_mem_sect_under_node from there
with check_nid set to false.  Without a node that function returns
having not done the sysfs related stuff as there is no node to use.
This is expected but it is the resulting path that fails...

Exact path to the problem is as follows:

 mm/memory_hotplug.c: add_memory_resource()

   The node is not online so we enter the 'if (new_node)' twice, on the
   second such block there is a call to link_mem_sections which calls
   into

  drivers/node.c: link_mem_sections() which calls

  drivers/node.c: register_mem_sect_under_node() which calls
     get_nid_for_pfn and keeps trying until the output of that matches
     the expected node (passed all the way down from
     add_memory_resource)

It is effectively the same fix as the one referred to in the fixes tag
just in the code path for a new node where the comments point out we
have to rerun the link creation because it will have failed in
register_new_memory (as there was no node at the time).  (actually that
comment is wrong now as we don't have register_new_memory any more it
got renamed to hotplug_memory_register in Pavel's patch).

Link: http://lkml.kernel.org/r/20180504085311.1240-1-Jonathan.Cameron@huawei.com
Fixes: fc44f7f9 ("mm/memory_hotplug: don't read nid from struct page during hotplug")
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: NPavel Tatashin <pasha.tatashin@oracle.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Oscar has reported:
: Due to an unfortunate setting with movablecore, memblocks containing bootmem
: memory (pages marked by get_page_bootmem()) ended up marked in zone_movable.
: So while trying to remove that memory, the system failed in do_migrate_range
: and __offline_pages never returned.
:
: This can be reproduced by running
: qemu-system-x86_64 -m 6G,slots=8,maxmem=8G -numa node,mem=4096M -numa node,mem=2048M
: and movablecore=4G kernel command line
:
: linux kernel: BIOS-provided physical RAM map:
: linux kernel: BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
: linux kernel: BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
: linux kernel: BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
: linux kernel: BIOS-e820: [mem 0x0000000000100000-0x00000000bffdffff] usable
: linux kernel: BIOS-e820: [mem 0x00000000bffe0000-0x00000000bfffffff] reserved
: linux kernel: BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
: linux kernel: BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
: linux kernel: BIOS-e820: [mem 0x0000000100000000-0x00000001bfffffff] usable
: linux kernel: NX (Execute Disable) protection: active
: linux kernel: SMBIOS 2.8 present.
: linux kernel: DMI: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org
: linux kernel: Hypervisor detected: KVM
: linux kernel: e820: update [mem 0x00000000-0x00000fff] usable ==> reserved
: linux kernel: e820: remove [mem 0x000a0000-0x000fffff] usable
: linux kernel: last_pfn = 0x1c0000 max_arch_pfn = 0x400000000
:
: linux kernel: SRAT: PXM 0 -> APIC 0x00 -> Node 0
: linux kernel: SRAT: PXM 1 -> APIC 0x01 -> Node 1
: linux kernel: ACPI: SRAT: Node 0 PXM 0 [mem 0x00000000-0x0009ffff]
: linux kernel: ACPI: SRAT: Node 0 PXM 0 [mem 0x00100000-0xbfffffff]
: linux kernel: ACPI: SRAT: Node 0 PXM 0 [mem 0x100000000-0x13fffffff]
: linux kernel: ACPI: SRAT: Node 1 PXM 1 [mem 0x140000000-0x1bfffffff]
: linux kernel: ACPI: SRAT: Node 0 PXM 0 [mem 0x1c0000000-0x43fffffff] hotplug
: linux kernel: NUMA: Node 0 [mem 0x00000000-0x0009ffff] + [mem 0x00100000-0xbfffffff] -> [mem 0x0
: linux kernel: NUMA: Node 0 [mem 0x00000000-0xbfffffff] + [mem 0x100000000-0x13fffffff] -> [mem 0
: linux kernel: NODE_DATA(0) allocated [mem 0x13ffd6000-0x13fffffff]
: linux kernel: NODE_DATA(1) allocated [mem 0x1bffd3000-0x1bfffcfff]
:
: zoneinfo shows that the zone movable is placed into both numa nodes:
: Node 0, zone  Movable
:   pages free     160140
:         min      1823
:         low      2278
:         high     2733
:         spanned  262144
:         present  262144
:         managed  245670
: Node 1, zone  Movable
:   pages free     448427
:         min      3827
:         low      4783
:         high     5739
:         spanned  524288
:         present  524288
:         managed  515766

Note how only Node 0 has a hutplugable memory region which would rule it
out from the early memblock allocations (most likely memmap).  Node1
will surely contain memmaps on the same node and those would prevent
offlining to succeed.  So this is arguably a configuration issue.
Although one could argue that we should be more clever and rule early
allocations from the zone movable.  This would be correct but probably
not worth the effort considering what a hack movablecore is.

Anyway, We could do better for those cases though.  We rely on
start_isolate_page_range resp.  has_unmovable_pages to do their job.
The first one isolates the whole range to be offlined so that we do not
allocate from it anymore and the later makes sure we are not stumbling
over non-migrateable pages.

has_unmovable_pages is overly optimistic, however.  It doesn't check all
the pages if we are withing zone_movable because we rely that those
pages will be always migrateable.  As it turns out we are still not
perfect there.  While bootmem pages in zonemovable sound like a clear
bug which should be fixed let's remove the optimization for now and warn
if we encounter unmovable pages in zone_movable in the meantime.  That
should help for now at least.

Btw.  this wasn't a real problem until commit 72b39cfc ("mm,
memory_hotplug: do not fail offlining too early") because we used to
have a small number of retries and then failed.  This turned out to be
too fragile though.

Link: http://lkml.kernel.org/r/20180523125555.30039-2-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Reported-by: NOscar Salvador <osalvador@techadventures.net>
Tested-by: NOscar Salvador <osalvador@techadventures.net>
Reviewed-by: NPavel Tatashin <pasha.tatashin@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

KASAN uses different routines to map shadow for hot added memory and
memory obtained in boot process.  Attempt to offline memory onlined by
normal boot process leads to this:

    Trying to vfree() nonexistent vm area (000000005d3b34b9)
    WARNING: CPU: 2 PID: 13215 at mm/vmalloc.c:1525 __vunmap+0x147/0x190

    Call Trace:
     kasan_mem_notifier+0xad/0xb9
     notifier_call_chain+0x166/0x260
     __blocking_notifier_call_chain+0xdb/0x140
     __offline_pages+0x96a/0xb10
     memory_subsys_offline+0x76/0xc0
     device_offline+0xb8/0x120
     store_mem_state+0xfa/0x120
     kernfs_fop_write+0x1d5/0x320
     __vfs_write+0xd4/0x530
     vfs_write+0x105/0x340
     SyS_write+0xb0/0x140

Obviously we can't call vfree() to free memory that wasn't allocated via
vmalloc().  Use find_vm_area() to see if we can call vfree().

Unfortunately it's a bit tricky to properly unmap and free shadow
allocated during boot, so we'll have to keep it.  If memory will come
online again that shadow will be reused.

Matthew asked: how can you call vfree() on something that isn't a
vmalloc address?

  vfree() is able to free any address returned by
  __vmalloc_node_range().  And __vmalloc_node_range() gives you any
  address you ask.  It doesn't have to be an address in [VMALLOC_START,
  VMALLOC_END] range.

  That's also how the module_alloc()/module_memfree() works on
  architectures that have designated area for modules.

[aryabinin@virtuozzo.com: improve comments]
  Link: http://lkml.kernel.org/r/dabee6ab-3a7a-51cd-3b86-5468718e0390@virtuozzo.com
[akpm@linux-foundation.org: fix typos, reflow comment]
Link: http://lkml.kernel.org/r/20180201163349.8700-1-aryabinin@virtuozzo.com
Fixes: fa69b598 ("mm/kasan: add support for memory hotplug")
Signed-off-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reported-by: NPaul Menzel <pmenzel+linux-kasan-dev@molgen.mpg.de>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>