Merge tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

 - Nick Piggin's "shoot lazy tlbs" series, to improve the peformance of
   switching from a user process to a kernel thread.

 - More folio conversions from Kefeng Wang, Zhang Peng and Pankaj
   Raghav.

 - zsmalloc performance improvements from Sergey Senozhatsky.

 - Yue Zhao has found and fixed some data race issues around the
   alteration of memcg userspace tunables.

 - VFS rationalizations from Christoph Hellwig:
     - removal of most of the callers of write_one_page()
     - make __filemap_get_folio()'s return value more useful

 - Luis Chamberlain has changed tmpfs so it no longer requires swap
   backing. Use `mount -o noswap'.

 - Qi Zheng has made the slab shrinkers operate locklessly, providing
   some scalability benefits.

 - Keith Busch has improved dmapool's performance, making part of its
   operations O(1) rather than O(n).

 - Peter Xu adds the UFFD_FEATURE_WP_UNPOPULATED feature to userfaultd,
   permitting userspace to wr-protect anon memory unpopulated ptes.

 - Kirill Shutemov has changed MAX_ORDER's meaning to be inclusive
   rather than exclusive, and has fixed a bunch of errors which were
   caused by its unintuitive meaning.

 - Axel Rasmussen give userfaultfd the UFFDIO_CONTINUE_MODE_WP feature,
   which causes minor faults to install a write-protected pte.

 - Vlastimil Babka has done some maintenance work on vma_merge():
   cleanups to the kernel code and improvements to our userspace test
   harness.

 - Cleanups to do_fault_around() by Lorenzo Stoakes.

 - Mike Rapoport has moved a lot of initialization code out of various
   mm/ files and into mm/mm_init.c.

 - Lorenzo Stoakes removd vmf_insert_mixed_prot(), which was added for
   DRM, but DRM doesn't use it any more.

 - Lorenzo has also coverted read_kcore() and vread() to use iterators
   and has thereby removed the use of bounce buffers in some cases.

 - Lorenzo has also contributed further cleanups of vma_merge().

 - Chaitanya Prakash provides some fixes to the mmap selftesting code.

 - Matthew Wilcox changes xfs and afs so they no longer take sleeping
   locks in ->map_page(), a step towards RCUification of pagefaults.

 - Suren Baghdasaryan has improved mmap_lock scalability by switching to
   per-VMA locking.

 - Frederic Weisbecker has reworked the percpu cache draining so that it
   no longer causes latency glitches on cpu isolated workloads.

 - Mike Rapoport cleans up and corrects the ARCH_FORCE_MAX_ORDER Kconfig
   logic.

 - Liu Shixin has changed zswap's initialization so we no longer waste a
   chunk of memory if zswap is not being used.

 - Yosry Ahmed has improved the performance of memcg statistics
   flushing.

 - David Stevens has fixed several issues involving khugepaged,
   userfaultfd and shmem.

 - Christoph Hellwig has provided some cleanup work to zram's IO-related
   code paths.

 - David Hildenbrand has fixed up some issues in the selftest code's
   testing of our pte state changing.

 - Pankaj Raghav has made page_endio() unneeded and has removed it.

 - Peter Xu contributed some rationalizations of the userfaultfd
   selftests.

 - Yosry Ahmed has fixed an issue around memcg's page recalim
   accounting.

 - Chaitanya Prakash has fixed some arm-related issues in the
   selftests/mm code.

 - Longlong Xia has improved the way in which KSM handles hwpoisoned
   pages.

 - Peter Xu fixes a few issues with uffd-wp at fork() time.

 - Stefan Roesch has changed KSM so that it may now be used on a
   per-process and per-cgroup basis.

* tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (369 commits)
  mm,unmap: avoid flushing TLB in batch if PTE is inaccessible
  shmem: restrict noswap option to initial user namespace
  mm/khugepaged: fix conflicting mods to collapse_file()
  sparse: remove unnecessary 0 values from rc
  mm: move 'mmap_min_addr' logic from callers into vm_unmapped_area()
  hugetlb: pte_alloc_huge() to replace huge pte_alloc_map()
  maple_tree: fix allocation in mas_sparse_area()
  mm: do not increment pgfault stats when page fault handler retries
  zsmalloc: allow only one active pool compaction context
  selftests/mm: add new selftests for KSM
  mm: add new KSM process and sysfs knobs
  mm: add new api to enable ksm per process
  mm: shrinkers: fix debugfs file permissions
  mm: don't check VMA write permissions if the PTE/PMD indicates write permissions
  migrate_pages_batch: fix statistics for longterm pin retry
  userfaultfd: use helper function range_in_vma()
  lib/show_mem.c: use for_each_populated_zone() simplify code
  mm: correct arg in reclaim_pages()/reclaim_clean_pages_from_list()
  fs/buffer: convert create_page_buffers to folio_create_buffers
  fs/buffer: add folio_create_empty_buffers helper
  ...

4 files changed, 48 insertions, 6 deletions

diff --git a/Documentation/mm/active_mm.rst b/Documentation/mm/active_mm.rst
index 45d89f8fb3a8..d096fc091e23 100644
--- a/Documentation/mm/active_mm.rst
+++ b/Documentation/mm/active_mm.rst
@@ -2,6 +2,12 @@
 Active MM
 =========
 
+Note, the mm_count refcount may no longer include the "lazy" users
+(running tasks with ->active_mm == mm && ->mm == NULL) on kernels
+with CONFIG_MMU_LAZY_TLB_REFCOUNT=n. Taking and releasing these lazy
+references must be done with mmgrab_lazy_tlb() and mmdrop_lazy_tlb()
+helpers, which abstract this config option.
+
 ::
 
  List:       linux-kernel
diff --git a/Documentation/mm/arch_pgtable_helpers.rst b/Documentation/mm/arch_pgtable_helpers.rst
index 30d9a09f01f4..af3891f895b0 100644
--- a/Documentation/mm/arch_pgtable_helpers.rst
+++ b/Documentation/mm/arch_pgtable_helpers.rst
@@ -214,7 +214,7 @@ HugeTLB Page Table Helpers
 +---------------------------+--------------------------------------------------+
 | pte_huge                  | Tests a HugeTLB                                  |
 +---------------------------+--------------------------------------------------+
-| pte_mkhuge                | Creates a HugeTLB                                |
+| arch_make_huge_pte        | Creates a HugeTLB                                |
 +---------------------------+--------------------------------------------------+
 | huge_pte_dirty            | Tests a dirty HugeTLB                            |
 +---------------------------+--------------------------------------------------+
diff --git a/Documentation/mm/multigen_lru.rst b/Documentation/mm/multigen_lru.rst
index 5f1f6ecbb79b..52ed5092022f 100644
--- a/Documentation/mm/multigen_lru.rst
+++ b/Documentation/mm/multigen_lru.rst
@@ -103,7 +103,8 @@ moving across tiers only involves atomic operations on
 ``folio->flags`` and therefore has a negligible cost. A feedback loop
 modeled after the PID controller monitors refaults over all the tiers
 from anon and file types and decides which tiers from which types to
-evict or protect.
+evict or protect. The desired effect is to balance refault percentages
+between anon and file types proportional to the swappiness level.
 
 There are two conceptually independent procedures: the aging and the
 eviction. They form a closed-loop system, i.e., the page reclaim.
@@ -156,6 +157,27 @@ This time-based approach has the following advantages:
    and memory sizes.
 2. It is more reliable because it is directly wired to the OOM killer.
 
+``mm_struct`` list
+------------------
+An ``mm_struct`` list is maintained for each memcg, and an
+``mm_struct`` follows its owner task to the new memcg when this task
+is migrated.
+
+A page table walker iterates ``lruvec_memcg()->mm_list`` and calls
+``walk_page_range()`` with each ``mm_struct`` on this list to scan
+PTEs. When multiple page table walkers iterate the same list, each of
+them gets a unique ``mm_struct``, and therefore they can run in
+parallel.
+
+Page table walkers ignore any misplaced pages, e.g., if an
+``mm_struct`` was migrated, pages left in the previous memcg will be
+ignored when the current memcg is under reclaim. Similarly, page table
+walkers will ignore pages from nodes other than the one under reclaim.
+
+This infrastructure also tracks the usage of ``mm_struct`` between
+context switches so that page table walkers can skip processes that
+have been sleeping since the last iteration.
+
 Rmap/PT walk feedback
 ---------------------
 Searching the rmap for PTEs mapping each page on an LRU list (to test
@@ -170,7 +192,7 @@ promotes hot pages. If the scan was done cacheline efficiently, it
 adds the PMD entry pointing to the PTE table to the Bloom filter. This
 forms a feedback loop between the eviction and the aging.
 
-Bloom Filters
+Bloom filters
 -------------
 Bloom filters are a space and memory efficient data structure for set
 membership test, i.e., test if an element is not in the set or may be
@@ -186,6 +208,18 @@ is false positive, the cost is an additional scan of a range of PTEs,
 which may yield hot pages anyway. Parameters of the filter itself can
 control the false positive rate in the limit.
 
+PID controller
+--------------
+A feedback loop modeled after the Proportional-Integral-Derivative
+(PID) controller monitors refaults over anon and file types and
+decides which type to evict when both types are available from the
+same generation.
+
+The PID controller uses generations rather than the wall clock as the
+time domain because a CPU can scan pages at different rates under
+varying memory pressure. It calculates a moving average for each new
+generation to avoid being permanently locked in a suboptimal state.
+
 Memcg LRU
 ---------
 An memcg LRU is a per-node LRU of memcgs. It is also an LRU of LRUs,
@@ -223,9 +257,9 @@ parts:
 
 * Generations
 * Rmap walks
-* Page table walks
-* Bloom filters
-* PID controller
+* Page table walks via ``mm_struct`` list
+* Bloom filters for rmap/PT walk feedback
+* PID controller for refault feedback
 
 The aging and the eviction form a producer-consumer model;
 specifically, the latter drives the former by the sliding window over
diff --git a/Documentation/mm/unevictable-lru.rst b/Documentation/mm/unevictable-lru.rst
index 92ac5dca420c..d5ac8511eb67 100644
--- a/Documentation/mm/unevictable-lru.rst
+++ b/Documentation/mm/unevictable-lru.rst
@@ -42,6 +42,8 @@ The unevictable list addresses the following classes of unevictable pages:
 
  * Those owned by ramfs.
 
+ * Those owned by tmpfs with the noswap mount option.
+
  * Those mapped into SHM_LOCK'd shared memory regions.
 
  * Those mapped into VM_LOCKED [mlock()ed] VMAs.