Merge branch 'akpm' (patches from Andrew)

Merge more updates from Andrew Morton:
 "190 patches.

  Subsystems affected by this patch series: mm (hugetlb, userfaultfd,
  vmscan, kconfig, proc, z3fold, zbud, ras, mempolicy, memblock,
  migration, thp, nommu, kconfig, madvise, memory-hotplug, zswap,
  zsmalloc, zram, cleanups, kfence, and hmm), procfs, sysctl, misc,
  core-kernel, lib, lz4, checkpatch, init, kprobes, nilfs2, hfs,
  signals, exec, kcov, selftests, compress/decompress, and ipc"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits)
  ipc/util.c: use binary search for max_idx
  ipc/sem.c: use READ_ONCE()/WRITE_ONCE() for use_global_lock
  ipc: use kmalloc for msg_queue and shmid_kernel
  ipc sem: use kvmalloc for sem_undo allocation
  lib/decompressors: remove set but not used variabled 'level'
  selftests/vm/pkeys: exercise x86 XSAVE init state
  selftests/vm/pkeys: refill shadow register after implicit kernel write
  selftests/vm/pkeys: handle negative sys_pkey_alloc() return code
  selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random
  kcov: add __no_sanitize_coverage to fix noinstr for all architectures
  exec: remove checks in __register_bimfmt()
  x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned
  hfsplus: report create_date to kstat.btime
  hfsplus: remove unnecessary oom message
  nilfs2: remove redundant continue statement in a while-loop
  kprobes: remove duplicated strong free_insn_page in x86 and s390
  init: print out unknown kernel parameters
  checkpatch: do not complain about positive return values starting with EPOLL
  checkpatch: improve the indented label test
  checkpatch: scripts/spdxcheck.py now requires python3
  ...

5 files changed, 49 insertions, 1 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0315407f5f57..13f13fdd4731 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1594,6 +1594,23 @@
 			Documentation/admin-guide/mm/hugetlbpage.rst.
 			Format: size[KMG]
 
+	hugetlb_free_vmemmap=
+			[KNL] Reguires CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
+			enabled.
+			Allows heavy hugetlb users to free up some more
+			memory (6 * PAGE_SIZE for each 2MB hugetlb page).
+			Format: { on | off (default) }
+
+			on:  enable the feature
+			off: disable the feature
+
+			Built with CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON=y,
+			the default is on.
+
+			This is not compatible with memory_hotplug.memmap_on_memory.
+			If both parameters are enabled, hugetlb_free_vmemmap takes
+			precedence over memory_hotplug.memmap_on_memory.
+
 	hung_task_panic=
 			[KNL] Should the hung task detector generate panics.
 			Format: 0 | 1
@@ -2860,6 +2877,10 @@
 			Note that even when enabled, there are a few cases where
 			the feature is not effective.
 
+			This is not compatible with hugetlb_free_vmemmap. If
+			both parameters are enabled, hugetlb_free_vmemmap takes
+			precedence over memory_hotplug.memmap_on_memory.
+
 	memtest=	[KNL,X86,ARM,PPC,RISCV] Enable memtest
 			Format: <integer>
 			default : 0 <disable>
diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
index f7b1c7462991..8abaeb144e44 100644
--- a/Documentation/admin-guide/mm/hugetlbpage.rst
+++ b/Documentation/admin-guide/mm/hugetlbpage.rst
@@ -60,6 +60,10 @@ HugePages_Surp
         the pool above the value in ``/proc/sys/vm/nr_hugepages``. The
         maximum number of surplus huge pages is controlled by
         ``/proc/sys/vm/nr_overcommit_hugepages``.
+	Note: When the feature of freeing unused vmemmap pages associated
+	with each hugetlb page is enabled, the number of surplus huge pages
+	may be temporarily larger than the maximum number of surplus huge
+	pages when the system is under memory pressure.
 Hugepagesize
 	is the default hugepage size (in Kb).
 Hugetlb
@@ -80,6 +84,10 @@ returned to the huge page pool when freed by a task.  A user with root
 privileges can dynamically allocate more or free some persistent huge pages
 by increasing or decreasing the value of ``nr_hugepages``.
 
+Note: When the feature of freeing unused vmemmap pages associated with each
+hugetlb page is enabled, we can fail to free the huge pages triggered by
+the user when ths system is under memory pressure.  Please try again later.
+
 Pages that are used as huge pages are reserved inside the kernel and cannot
 be used for other purposes.  Huge pages cannot be swapped out under
 memory pressure.
@@ -145,6 +153,9 @@ default_hugepagesz
 
 	will all result in 256 2M huge pages being allocated.  Valid default
 	huge page size is architecture dependent.
+hugetlb_free_vmemmap
+	When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, this enables freeing
+	unused vmemmap pages associated with each HugeTLB page.
 
 When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages``
 indicates the current number of pre-allocated huge pages of the default size.
diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index 05d51d2d8beb..c6bae2d77160 100644
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -357,6 +357,19 @@ creates ZONE_MOVABLE as following.
    Unfortunately, there is no information to show which memory block belongs
    to ZONE_MOVABLE. This is TBD.
 
+   Memory offlining can fail when dissolving a free huge page on ZONE_MOVABLE
+   and the feature of freeing unused vmemmap pages associated with each hugetlb
+   page is enabled.
+
+   This can happen when we have plenty of ZONE_MOVABLE memory, but not enough
+   kernel memory to allocate vmemmmap pages.  We may even be able to migrate
+   huge page contents, but will not be able to dissolve the source huge page.
+   This will prevent an offline operation and is unfortunate as memory offlining
+   is expected to succeed on movable zones.  Users that depend on memory hotplug
+   to succeed for movable zones should carefully consider whether the memory
+   savings gained from this feature are worth the risk of possibly not being
+   able to offline memory in certain situations.
+
 .. note::
    Techniques that rely on long-term pinnings of memory (especially, RDMA and
    vfio) are fundamentally problematic with ZONE_MOVABLE and, therefore, memory
diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
index 340a5aee9b80..fb578fbbb76c 100644
--- a/Documentation/admin-guide/mm/pagemap.rst
+++ b/Documentation/admin-guide/mm/pagemap.rst
@@ -21,6 +21,8 @@ There are four components to pagemap:
     * Bit  55    pte is soft-dirty (see
       :ref:`Documentation/admin-guide/mm/soft-dirty.rst <soft_dirty>`)
     * Bit  56    page exclusively mapped (since 4.2)
+    * Bit  57    pte is uffd-wp write-protected (since 5.13) (see
+      :ref:`Documentation/admin-guide/mm/userfaultfd.rst <userfaultfd>`)
     * Bits 57-60 zero
     * Bit  61    page is file-page or shared-anon (since 3.5)
     * Bit  62    page swapped
diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst
index 3aa38e8b8361..6528036093e1 100644
--- a/Documentation/admin-guide/mm/userfaultfd.rst
+++ b/Documentation/admin-guide/mm/userfaultfd.rst
@@ -77,7 +77,8 @@ events, except page fault notifications, may be generated:
 
 - ``UFFD_FEATURE_MINOR_HUGETLBFS`` indicates that the kernel supports
   ``UFFDIO_REGISTER_MODE_MINOR`` registration for hugetlbfs virtual memory
-  areas.
+  areas. ``UFFD_FEATURE_MINOR_SHMEM`` is the analogous feature indicating
+  support for shmem virtual memory areas.
 
 The userland application should set the feature flags it intends to use
 when invoking the ``UFFDIO_API`` ioctl, to request that those features be