linux.git/mm/migrate.c, branch v6.14

mm/migrate: fix shmem xarray update during migration

2025-03-17T00:40:24+00:00

A shmem folio can be either in page cache or in swap cache, but not at the
same time.  Namely, once it is in swap cache, folio->mapping should be
NULL, and the folio is no longer in a shmem mapping.

In __folio_migrate_mapping(), to determine the number of xarray entries to
update, folio_test_swapbacked() is used, but that conflates shmem in page
cache case and shmem in swap cache case.  It leads to xarray multi-index
entry corruption, since it turns a sibling entry to a normal entry during
xas_store() (see [1] for a userspace reproduction).  Fix it by only using
folio_test_swapcache() to determine whether xarray is storing swap cache
entries or not to choose the right number of xarray entries to update.

[1] https://lore.kernel.org/linux-mm/Z8idPCkaJW1IChjT@casper.infradead.org/

Note:
In __split_huge_page(), folio_test_anon() && folio_test_swapcache() is
used to get swap_cache address space, but that ignores the shmem folio in
swap cache case.  It could lead to NULL pointer dereferencing when a
in-swap-cache shmem folio is split at __xa_store(), since
!folio_test_anon() is true and folio->mapping is NULL.  But fortunately,
its caller split_huge_page_to_list_to_order() bails out early with EBUSY
when folio->mapping is NULL.  So no need to take care of it here.

Link: https://lkml.kernel.org/r/20250305200403.2822855-1-ziy@nvidia.com
Fixes: fc346d0a70a1 ("mm: migrate high-order folios in swap cache correctly")
Signed-off-by: Zi Yan 
Reported-by: Liu Shixin 
Closes: https://lore.kernel.org/all/28546fb4-5210-bf75-16d6-43e1f8646080@huawei.com/
Suggested-by: Hugh Dickins 
Reviewed-by: Matthew Wilcox (Oracle) 
Reviewed-by: Baolin Wang 
Cc: Barry Song 
Cc: Charan Teja Kalla 
Cc: David Hildenbrand 
Cc: Hugh Dickins 
Cc: Kefeng Wang 
Cc: Lance Yang 
Cc: Ryan Roberts 
Cc: 
Signed-off-by: Andrew Morton

mm: separate move/undo parts from migrate_pages_batch()

2025-01-26T04:22:45+00:00

Functionally, no change.  This is a preparation for luf mechanism that
requires to use separated folio lists for its own handling during
migration.  Refactored migrate_pages_batch() so as to separate move/undo
parts from migrate_pages_batch().

Link: https://lkml.kernel.org/r/20250115103403.11882-1-byungchul@sk.com
Signed-off-by: Byungchul Park 
Reviewed-by: Shivank Garg 
Reviewed-by: Zi Yan 
Signed-off-by: Andrew Morton

mm/hugetlb: rename folio_putback_active_hugetlb() to folio_putback_hugetlb()

2025-01-26T04:22:42+00:00

Now that folio_putback_hugetlb() is only called on folios that were
previously isolated through folio_isolate_hugetlb(), let's rename it to
match folio_putback_lru().

Add some kernel doc to clarify how this function is supposed to be used.

Link: https://lkml.kernel.org/r/20250113131611.2554758-5-david@redhat.com
Signed-off-by: David Hildenbrand 
Reviewed-by: Baolin Wang 
Cc: Matthew Wilcox (Oracle) 
Cc: Muchun Song 
Cc: Sidhartha Kumar 
Signed-off-by: Andrew Morton

mm/migrate: don't call folio_putback_active_hugetlb() on dst hugetlb folio

2025-01-26T04:22:41+00:00

We replaced a simple put_page() by a putback_active_hugepage() call in
commit 3aaa76e125c1 ("mm: migrate: hugetlb: putback destination hugepage
to active list"), to set the "active" flag on the dst hugetlb folio.

Nowadays, we decoupled the "active" list from the flag, by calling the
flag "migratable".

Calling "putback" on something that wasn't allocated is weird and not
future proof, especially if we might reach that path when migration failed
and we just want to free the freshly allocated hugetlb folio.

Let's simply handle the migratable flag and the active list flag in
move_hugetlb_state(), where we know that allocation succeeded and already
handle the temporary flag; use a simple folio_put() to return our
reference.

Link: https://lkml.kernel.org/r/20250113131611.2554758-4-david@redhat.com
Signed-off-by: David Hildenbrand 
Reviewed-by: Baolin Wang 
Cc: Matthew Wilcox (Oracle) 
Cc: Muchun Song 
Cc: Sidhartha Kumar 
Signed-off-by: Andrew Morton

mm/hugetlb: rename isolate_hugetlb() to folio_isolate_hugetlb()

2025-01-26T04:22:41+00:00

Let's make the function name match "folio_isolate_lru()", and add some
kernel doc.

Link: https://lkml.kernel.org/r/20250113131611.2554758-3-david@redhat.com
Signed-off-by: David Hildenbrand 
Reviewed-by: Matthew Wilcox (Oracle) 
Reviewed-by: Baolin Wang 
Cc: Muchun Song 
Cc: Sidhartha Kumar 
Signed-off-by: Andrew Morton

mm/migrate: remove slab checks in isolate_movable_page()

2025-01-14T06:40:58+00:00

Commit 8b8817630ae8 ("mm/migrate: make isolate_movable_page() skip slab
pages") introduced slab checks to prevent mis-identification of slab pages
as movable kernel pages.

However, after Matthew's frozen folio series, these slab checks became
unnecessary as the migration logic fails to increase the reference count
for frozen slab folios.  Remove these redundant slab checks and associated
memory barriers.

Link: https://lkml.kernel.org/r/20241210124807.8584-1-42.hyeyoo@gmail.com
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: David Hildenbrand 
Reviewed-by: Vlastimil Babka 
Acked-by: David Rientjes 
Cc: Christoph Lameter 
Cc: Joonsoo Kim 
Cc: Matthew Wilcox 
Cc: Pekka Enberg 
Cc: Roman Gushchin 
Signed-off-by: Andrew Morton

mm: migrate: remove unused argument vma from migrate_misplaced_folio()

2025-01-14T06:40:30+00:00

Commit ee86814b0562 ("mm/migrate: move NUMA hinting fault folio isolation
+ checks under PTL") removed the code that had used the vma argument in
migrate_misplaced_folio.

Since the vma argument was no longer used in migrate_misplaced_folio, this
patch removes it.

Link: https://lkml.kernel.org/r/20241126155655.466186-1-donettom@linux.ibm.com
Signed-off-by: Donet Tom 
Reviewed-by: Baolin Wang 
Reviewed-by: Zi Yan 
Acked-by: David Hildenbrand 
Cc: Ritesh Harjani (IBM) 
Signed-off-by: Andrew Morton

mm/codetag: swap tags when migrate pages

2024-12-06T03:54:46+00:00

Current solution to adjust codetag references during page migration is
done in 3 steps:

1. sets the codetag reference of the old page as empty (not pointing
   to any codetag);

2. subtracts counters of the new page to compensate for its own
   allocation;

3. sets codetag reference of the new page to point to the codetag of
   the old page.

This does not work if CONFIG_MEM_ALLOC_PROFILING_DEBUG=n because
set_codetag_empty() becomes NOOP.  Instead, let's simply swap codetag
references so that the new page is referencing the old codetag and the old
page is referencing the new codetag.  This way accounting stays valid and
the logic makes more sense.

Link: https://lkml.kernel.org/r/20241129025213.34836-1-00107082@163.com
Fixes: e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()")
Signed-off-by: David Wang <00107082@163.com>
Closes: https://lore.kernel.org/lkml/20241124074318.399027-1-00107082@163.com/
Acked-by: Suren Baghdasaryan 
Suggested-by: Suren Baghdasaryan 
Acked-by: Yu Zhao 
Cc: Kent Overstreet 
Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2024-11-18-19-27' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-11-23T17:58:07+00:00

Pull MM updates from Andrew Morton:

- The series "zram: optimal post-processing target selection" from
Sergey Senozhatsky improves zram's post-processing selection
algorithm. This leads to improved memory savings.

- Wei Yang has gone to town on the mapletree code, contributing several
series which clean up the implementation:
- "refine mas_mab_cp()"
- "Reduce the space to be cleared for maple_big_node"
- "maple_tree: simplify mas_push_node()"
- "Following cleanup after introduce mas_wr_store_type()"
- "refine storing null"

- The series "selftests/mm: hugetlb_fault_after_madv improvements" from
David Hildenbrand fixes this selftest for s390.

- The series "introduce pte_offset_map_{ro|rw}_nolock()" from Qi Zheng
implements some rationaizations and cleanups in the page mapping
code.

- The series "mm: optimize shadow entries removal" from Shakeel Butt
optimizes the file truncation code by speeding up the handling of
shadow entries.

- The series "Remove PageKsm()" from Matthew Wilcox completes the
migration of this flag over to being a folio-based flag.

- The series "Unify hugetlb into arch_get_unmapped_area functions" from
Oscar Salvador implements a bunch of consolidations and cleanups in
the hugetlb code.

- The series "Do not shatter hugezeropage on wp-fault" from Dev Jain
takes away the wp-fault time practice of turning a huge zero page
into small pages. Instead we replace the whole thing with a THP. More
consistent cleaner and potentiall saves a large number of pagefaults.

- The series "percpu: Add a test case and fix for clang" from Andy
Shevchenko enhances and fixes the kernel's built in percpu test code.

- The series "mm/mremap: Remove extra vma tree walk" from Liam Howlett
optimizes mremap() by avoiding doing things which we didn't need to
do.

- The series "Improve the tmpfs large folio read performance" from
Baolin Wang teaches tmpfs to copy data into userspace at the folio
size rather than as individual pages. A 20% speedup was observed.

- The series "mm/damon/vaddr: Fix issue in
damon_va_evenly_split_region()" fro Zheng Yejian fixes DAMON
splitting.

- The series "memcg-v1: fully deprecate charge moving" from Shakeel
Butt removes the long-deprecated memcgv2 charge moving feature.

- The series "fix error handling in mmap_region() and refactor" from
Lorenzo Stoakes cleanup up some of the mmap() error handling and
addresses some potential performance issues.

- The series "x86/module: use large ROX pages for text allocations"
from Mike Rapoport teaches x86 to use large pages for
read-only-execute module text.

- The series "page allocation tag compression" from Suren Baghdasaryan
is followon maintenance work for the new page allocation profiling
feature.

- The series "page->index removals in mm" from Matthew Wilcox remove
most references to page->index in mm/. A slow march towards shrinking
struct page.

- The series "damon/{self,kunit}tests: minor fixups for DAMON debugfs
interface tests" from Andrew Paniakin performs maintenance work for
DAMON's self testing code.

- The series "mm: zswap swap-out of large folios" from Kanchana Sridhar
improves zswap's batching of compression and decompression. It is a
step along the way towards using Intel IAA hardware acceleration for
this zswap operation.

- The series "kasan: migrate the last module test to kunit" from
Sabyrzhan Tasbolatov completes the migration of the KASAN built-in
tests over to the KUnit framework.

- The series "implement lightweight guard pages" from Lorenzo Stoakes
permits userapace to place fault-generating guard pages within a
single VMA, rather than requiring that multiple VMAs be created for
this. Improved efficiencies for userspace memory allocators are
expected.

- The series "memcg: tracepoint for flushing stats" from JP Kobryn uses
tracepoints to provide increased visibility into memcg stats flushing
activity.

- The series "zram: IDLE flag handling fixes" from Sergey Senozhatsky
fixes a zram buglet which potentially affected performance.

- The series "mm: add more kernel parameters to control mTHP" from
Maíra Canal enhances our ability to control/configuremultisize THP
from the kernel boot command line.

- The series "kasan: few improvements on kunit tests" from Sabyrzhan
Tasbolatov has a couple of fixups for the KASAN KUnit tests.

- The series "mm/list_lru: Split list_lru lock into per-cgroup scope"
from Kairui Song optimizes list_lru memory utilization when lockdep
is enabled.

* tag 'mm-stable-2024-11-18-19-27' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (215 commits)
cma: enforce non-zero pageblock_order during cma_init_reserved_mem()
mm/kfence: add a new kunit test test_use_after_free_read_nofault()
zram: fix NULL pointer in comp_algorithm_show()
memcg/hugetlb: add hugeTLB counters to memcg
vmstat: call fold_vm_zone_numa_events() before show per zone NUMA event
mm: mmap_lock: check trace_mmap_lock_$type_enabled() instead of regcount
zram: ZRAM_DEF_COMP should depend on ZRAM
MAINTAINERS/MEMORY MANAGEMENT: add document files for mm
Docs/mm/damon: recommend academic papers to read and/or cite
mm: define general function pXd_init()
kmemleak: iommu/iova: fix transient kmemleak false positive
mm/list_lru: simplify the list_lru walk callback function
mm/list_lru: split the lock to per-cgroup scope
mm/list_lru: simplify reparenting and initial allocation
mm/list_lru: code clean up for reparenting
mm/list_lru: don't export list_lru_add
mm/list_lru: don't pass unnecessary key parameters
kasan: add kunit tests for kmalloc_track_caller, kmalloc_node_track_caller
kasan: change kasan_atomics kunit test as KUNIT_CASE_SLOW
kasan: use EXPORT_SYMBOL_IF_KUNIT to export symbols
...

Merge tag 'vfs-6.13.pagecache' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-11-18T17:54:32+00:00

Pull vfs pagecache updates from Christian Brauner:
 "Cleanup filesystem page flag usage: This continues the work to make
  the mappedtodisk/owner_2 flag available to filesystems which don't use
  buffer heads. Further patches remove uses of Private2. This brings us
  very close to being rid of it entirely"

* tag 'vfs-6.13.pagecache' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  migrate: Remove references to Private2
  ceph: Remove call to PagePrivate2()
  btrfs: Switch from using the private_2 flag to owner_2
  mm: Remove PageMappedToDisk
  nilfs2: Convert nilfs_copy_buffer() to use folios
  fs: Move clearing of mappedtodisk to buffer.c