Merge tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull more MM updates from Andrew Morton:

 - "mm/rmap: index MAP_PRIVATE file-backed folios by anonymous pgoff"
   (Lorenzo Stoakes)

   Index MAP_PRIVATE file-backed folios by their anonymous page offset
   to resolve confusion around reverse mapping for zeroed and CoW'd
   file-backed memory.

   Use this new VMA anonymous page offset tracking to eliminate index
   conflicts and lay the foundation for scalable CoW performance
   improvements.

 - "promote mapped executable folios after first usage for MGLRU"
   (Baolin Wang)

   Make MGLRU's protection of mapped executable file folios more
   reliable. Follow the classical LRU's logic, promoting mapped
   executable file folios after their first usage to give executable
   code a better chance to stay in memory and improve workload
   performance.

 - "mm: vmscan: fix node reclaim ignoring swappiness parameter" (Ridong
   Chen)

   Fix per-node proactive reclaim interface's ignoring the swappiness
   parameter when CONFIG_MEMCG is disabled by consolidating
   sc_swappiness() into a single function that checks
   proactive_swappiness regardless of kernel configuration.

 - "mm/vmscan: reduce lru_lock contention via vmstat-derived
   scan-balance cost" (Usama Arif)

   Reduce lru_lock contention in the reclaim path by deriving
   scan-balance costs from vmstat counters rather than lock-acquired
   producer updates.

   Read and decay these cost signals on the reclaim side under a
   dedicated per-lruvec lock, reducing total LRU lock wait time by over
   60% without impacting scan throughput.

 - "zram: fix zram issues reported by sashiko" (Sergey Senozhatsky)

   Fix two low-risk zram bugs which Sashiko spotted in drive-by review.

 - "Honor XA_FLAGS_ACCOUNT in xas_split_alloc() and charge to folio's
   memcg" (Zi Yan)

   Fix xas_split_alloc() by enabling target folio memcg charging during
   splits and adding the missing __GFP_ACCOUNT flag for proper XArray
   node memory accounting.

 - "selftests/mm: use pattern matching in .gitignore" (Pratyush Mallick)

   Replace hardcoded binary names in selftests/mm/.gitignore with a
   generic pattern-matching rule to automatically ignore generated test
   files and avoid manual updates when adding new tests.

 - "mm/page_ext: remove pgdat_page_ext_init()" (Sang-Heon Jeon)

   Make the incompatibility between FLATMEM and NUMA explicit in
   mm/Kconfig and remove the unused pgdat_page_ext_init() function.

 - "zram: fix zstd error paths and add parameter validation" (Haoqin
   Huang)

   Clean up zram compression backends by removing redundant error
   cleanup, adding parameter and dictionary validation, auto-prefixing
   algorithm error logs, and resetting parameters prior to
   reinitialization.

 - "zram: fix stale scan bounds after reinitialization" (Longlong Xia)

   Prevent out-of-bounds slot accesses during concurrent zram resets by
   moving table scan bound calculations under dev_lock in
   writeback_store() and read_block_state().

 - "add anon mTHP collapse test cases" (Baolin Wang)

   Extend selftests helper functions to support arbitrary page orders
   and add new test cases and options for mTHP collapse in khugepaged.

 - "selftests/mm: Handle unsupported and transient test conditions"
   (Muhammad Usama Anjum)

   Update MM selftests to report a SKIP status instead of a failure when
   required kernel or filesystem features are unsupported, while adding
   retry logic for transient page migration errors.

 - "mm/zswap: Fixes and improves the zswap shrink" (Hao Jia)

   Fix the missing zswap global shrinker when CONFIG_MEMCG is disabled
   and extend shrink_memcg() to support batch writeback for improved
   writeback efficiency.

 - "alloc_tag: introduce IOCTL-based filtering for MAP" (Suren
   Baghdasaryan)

   Introduce an IOCTL-based binary interface for memory allocation
   profiling that enables kernel-side filtering before per-CPU counter
   aggregation.

   This eliminates the text-parsing overhead of /proc/allocinfo and
   provides up to a 20x speedup by transferring only filtered allocation
   data to userspace.

 - "better block swap batching and a different take on swap_ops v5"
   (Christoph Hellwig)

   Refactor block swap I/O to use swap_iocb for batching instead of
   single-bio requests and rebase the swap_ops interface, achieving
   faster swap throughput during kernel builds.

 - "mm: kmemleak: reduce transient false positives by confirming leaks"
   (Catalin Marinas)

   Reduce false-positive kmemleak reports by combining two kmemleak
   enhancements that add a second confirmation scan and a configurable
   minimum unreferenced scan count module parameter.

 - "mm: kmemleak: default min_unref_scans to 2 for verbose kernels"
   (Breno Leitao)

   Auto-scanning kernels can generate false-positive memory leak reports
   on single scans, so this patch defaults min_unref_scans to 2 when
   CONFIG_DEBUG_KMEMLEAK_VERBOSE is enabled to require a second
   confirming scan.

 - "swap_ops updates" (Christoph Hellwig)

   Batching I/O for synchronous swap devices causes performance
   regressions and filesystem-based swap suffers from double-indirection
   overhead. This series resolves both issues by reintroducing per-folio
   writes for synchronous swap and allowing filesystems to directly
   export their own swap_ops.

 - "mm/khugepaged: several cleanups" (Nico Pache)

   khugepaged accumulated redundant state-checking patterns and outdated
   comments following mTHP integration. Introduce dedicated helpers for
   PTE validation and event counting while refreshing the internal
   documentation.

 - "maple_tree: lock checking and clean ups" (Liam Howlett)

   Syzbot reports incorrectly blame memory management exit paths for
   locking bugs, maple tree erase operations risk allocation failures
   without gfp flags and internal documentation lacks clarity.

   Improve lock error detection, update docs, fix race and allocation
   edge cases and optimize erase allocations using a fallback to
   GFP_KERNEL | GFP_NOFAIL.

* tag 'mm-stable-2026-08-26-15-22' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (172 commits)
  selftests/proc: make proc-maps-race work with READ_IMPLIES_EXEC
  memcg: move LRU size accounting on reparenting instead of copying it
  mm/vmscan: fix comment logic in balance_pgdat
  maple_tree: add helper mas_make_walkable()
  maple_tree: avoid extra gap calculation
  maple_tree: fix argument name in header
  maple_tree: change two GFP flags in tests
  maple_tree: document erase and allocations better
  maple_tree: avoid mas_erase() and mtree_erase() failures
  maple_tree: document that erase may use GFP_KERNEL for allocations
  maple_tree: catch race in mas_alloc_cyclic()
  maple_tree: add bulk parent set helper
  maple_tree: micro optimisation of mas_wr_store_type()
  maple_tree: optimise mas_wr_node_store() when not in rcu mode
  maple_tree: use prefetched value in mas_wr_store_type()
  maple_tree: clarify comments on mas_nomem()
  maple_tree: drop MAPLE_ALLOC_SLOTS
  maple_tree: drop dead code from mas_extend_spanning_null()
  maple_tree: documentation fix
  maple_tree: add write lock checking with lockdep sequence numbers
  ...

1 files changed, 20 insertions, 4 deletions

diff --git a/Documentation/core-api/maple_tree.rst b/Documentation/core-api/maple_tree.rst
index ccdd1615cf97..12bccfb6aac1 100644
--- a/Documentation/core-api/maple_tree.rst
+++ b/Documentation/core-api/maple_tree.rst
@@ -17,7 +17,8 @@ supports iterating over a range of entries and going to the previous or next
 entry in a cache-efficient manner.  The tree can also be put into an RCU-safe
 mode of operation which allows reading and writing concurrently.  Writers must
 synchronize on a lock, which can be the default spinlock, or the user can set
-the lock to an external lock of a different type.
+the lock to an external lock of a different type.  Note that external locks may
+interfere with allocations in a low memory situation.
 
 The Maple Tree maintains a small memory footprint and was designed to use
 modern processor cache efficiently.  The majority of the users will be able to
@@ -42,6 +43,15 @@ successful store operation within a given
 code segment when allocating cannot be done.  Allocations of nodes are
 relatively small at around 256 bytes.
 
+Since the maple tree uses internal nodes that are allocated and has rules on
+data density, erasing an entry may cause allocations to occur.  That is,
+erasing an entry may consume memory.  Users must take care to ensure that they
+do not violate the larger system constraints on when and how memory is
+allocated.  Most situations are fine to allocate, but the pre-allocation
+support is provided as a mechanism to avoid trickier situations.  There is also
+the possibility of using special entries and clean up the tree later, in
+extreme circumstances.
+
 .. _maple-tree-normal-api:
 
 Normal API
@@ -63,7 +73,10 @@ success or an error code otherwise.  mtree_store_range() works in the same way
 but takes a range.  mtree_load() is used to retrieve the entry stored at a
 given index.  You can use mtree_erase() to erase an entire range by only
 knowing one value within that range, or mtree_store() call with an entry of
-NULL may be used to partially erase a range or many ranges at once.
+NULL may be used to partially erase a range or many ranges at once.  Note that
+mtree_erase() may use GFP_KERNEL | __GFP_NOFAIL for allocations and cannot
+fail.  mtree_erase() can sleep, so it must not be called from an atomic
+context.
 
 If you want to only store a new entry to a range (or index) if that range is
 currently ``NULL``, you can use mtree_insert_range() or mtree_insert() which
@@ -163,7 +176,10 @@ You can use mas_erase() to erase an entire range by setting index and
 last of the maple state to the desired range to erase.  This will erase
 the first range that is found in that range, set the maple state index
 and last as the range that was erased and return the entry that existed
-at that location.
+at that location.  Note that mas_erase() may allocate with the GFP_KERNEL
+__GFP_NOFAIL and cannot fail, but may sleep.  If this is not okay, consider
+using mas_store_gfp() and pass it a ``NULL``,
+after setting up the correct range by walking to the entry.
 
 You can walk each entry within a range by using mas_for_each().  If you want
 to walk each element of the tree then ``0`` and ``ULONG_MAX`` may be used as
@@ -211,7 +227,7 @@ Advanced Locking
 
 The maple tree uses a spinlock by default, but external locks can be used for
 tree updates as well.  To use an external lock, the tree must be initialized
-with the ``MT_FLAGS_LOCK_EXTERN flag``, this is usually done with the
+with the ``MT_FLAGS_LOCK_EXTERN`` flag, this is usually done with the
 MTREE_INIT_EXT() #define, which takes an external lock as an argument.
 
 Functions and structures