linux.git/mm/page-writeback.c, branch v6.14

treewide: const qualify ctl_tables where applicable

2025-01-28T12:48:37+00:00

Add the const qualifier to all the ctl_tables in the tree except for
watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls,
loadpin_sysctl_table and the ones calling register_net_sysctl (./net,
drivers/inifiniband dirs). These are special cases as they use a
registration function with a non-const qualified ctl_table argument or
modify the arrays before passing them on to the registration function.

Constifying ctl_table structs will prevent the modification of
proc_handler function pointers as the arrays would reside in .rodata.
This is made possible after commit 78eb4ea25cd5 ("sysctl: treewide:
constify the ctl_table argument of proc_handlers") constified all the
proc_handlers.

Created this by running an spatch followed by a sed command:
Spatch:
    virtual patch

    @
    depends on !(file in "net")
    disable optional_qualifier
    @

    identifier table_name != {
      watchdog_hardlockup_sysctl,
      iwcm_ctl_table,
      ucma_ctl_table,
      memory_allocation_profiling_sysctls,
      loadpin_sysctl_table
    };
    @@

    + const
    struct ctl_table table_name [] = { ... };

sed:
    sed --in-place \
      -e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \
      kernel/utsname_sysctl.c

Reviewed-by: Song Liu 
Acked-by: Steven Rostedt (Google)  # for kernel/trace/
Reviewed-by: Martin K. Petersen  # SCSI
Reviewed-by: Darrick J. Wong  # xfs
Acked-by: Jani Nikula 
Acked-by: Corey Minyard 
Acked-by: Wei Liu 
Acked-by: Thomas Gleixner 
Reviewed-by: Bill O'Donnell 
Acked-by: Baoquan He 
Acked-by: Ashutosh Dixit 
Acked-by: Anna Schumaker 
Signed-off-by: Joel Granados

mm/page-writeback: consolidate wb_thresh bumping logic into __wb_calc_thresh

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

Address the feedback from 39ac99852fca ("mm/page-writeback: raise
wb_thresh to prevent write blocking with strictlimit)".  The wb_thresh
bumping logic is scattered across wb_position_ratio, __wb_calc_thresh, and
wb_update_dirty_ratelimit.  For consistency, consolidate all wb_thresh
bumping logic into __wb_calc_thresh.

Link: https://lkml.kernel.org/r/20241121100539.605818-1-jimzhao.ai@gmail.com
Signed-off-by: Jim Zhao 
Reviewed-by: Jan Kara 
Cc: Matthew Wilcox 
Cc: Kemeng Shi 
Cc: Guenter Roeck 
Signed-off-by: Andrew Morton

mm: fix div by zero in bdi_ratio_from_pages

2025-01-13T03:03:36+00:00

During testing it has been detected, that it is possible to get div by
zero error in bdi_set_min_bytes.  The error is caused by the function
bdi_ratio_from_pages().  bdi_ratio_from_pages() calls global_dirty_limits.
If the dirty threshold is 0, the div by zero is raised.  This can happen
if the root user is setting:

echo 0 > /proc/sys/vm/dirty_ratio

The following is a test case:

echo 0 > /proc/sys/vm/dirty_ratio
cd /sys/class/bdi/
echo 1 > strict_limit
echo 8192 > min_bytes

==> error is raised.

The problem is addressed by returning -EINVAL if dirty_ratio or
dirty_bytes is set to 0.

[shr@devkernel.io: check for -EINVAL in bdi_set_min_bytes() and bdi_set_max_bytes()]
  Link: https://lkml.kernel.org/r/20250108014723.166637-1-shr@devkernel.io
[shr@devkernel.io: v3]
  Link: https://lkml.kernel.org/r/20250109063411.6591-1-shr@devkernel.io
Link: https://lkml.kernel.org/r/20250104012037.159386-1-shr@devkernel.io
Signed-off-by: Stefan Roesch 
Reported-by: cheung wall 
Closes: https://lore.kernel.org/linux-mm/87pll35yd0.fsf@devkernel.io/T/#t
Acked-by: David Hildenbrand 
Cc: Matthew Wilcox (Oracle) 
Cc: Qiang Zhang 
Signed-off-by: Andrew Morton

Merge tag 'fuse-update-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2024-11-26T20:41:27+00:00

Pull fuse updates from Miklos Szeredi:

 - Add page -> folio conversions (Joanne Koong, Josef Bacik)

 - Allow max size of fuse requests to be configurable with a sysctl
   (Joanne Koong)

 - Allow FOPEN_DIRECT_IO to take advantage of async code path (yangyun)

 - Fix large kernel reads (like a module load) in virtio_fs (Hou Tao)

 - Fix attribute inconsistency in case readdirplus (and plain lookup in
   corner cases) is racing with inode eviction (Zhang Tianci)

 - Fix a WARN_ON triggered by virtio_fs (Asahi Lina)

* tag 'fuse-update-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (30 commits)
  virtiofs: dax: remove ->writepages() callback
  fuse: check attributes staleness on fuse_iget()
  fuse: remove pages for requests and exclusively use folios
  fuse: convert direct io to use folios
  mm/writeback: add folio_mark_dirty_lock()
  fuse: convert writebacks to use folios
  fuse: convert retrieves to use folios
  fuse: convert ioctls to use folios
  fuse: convert writes (non-writeback) to use folios
  fuse: convert reads to use folios
  fuse: convert readdir to use folios
  fuse: convert readlink to use folios
  fuse: convert cuse to use folios
  fuse: add support in virtio for requests using folios
  fuse: support folios in struct fuse_args_pages and fuse_copy_pages()
  fuse: convert fuse_notify_store to use folios
  fuse: convert fuse_retrieve to use folios
  fuse: use the folio based vmstat helpers
  fuse: convert fuse_writepage_need_send to take a folio
  fuse: convert fuse_do_readpage to use folios
  ...

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
...

memcg-v1: no need for memcg locking for writeback tracking

2024-11-07T04:11:19+00:00

During the era of memcg charge migration, the kernel has to be make
sure that the writeback stat updates do not race with the charge
migration.  Otherwise it might update the writeback stats of the wrong
memcg.  Now with the memcg charge migration gone, there is no more race
for writeback stat updates and the previous locking can be removed.

Link: https://lkml.kernel.org/r/20241025012304.2473312-5-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt 
Acked-by: Michal Hocko 
Reviewed-by: Roman Gushchin 
Acked-by: Johannes Weiner 
Cc: Hugh Dickins 
Cc: Muchun Song 
Cc: Yosry Ahmed 
Signed-off-by: Andrew Morton

memcg-v1: no need for memcg locking for dirty tracking

2024-11-07T04:11:19+00:00

During the era of memcg charge migration, the kernel has to be make
sure that the dirty stat updates do not race with the charge migration.
Otherwise it might update the dirty stats of the wrong memcg.  Now
with the memcg charge migration gone, there is no more race for dirty
stat updates and the previous locking can be removed.

Link: https://lkml.kernel.org/r/20241025012304.2473312-4-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt 
Acked-by: Michal Hocko 
Reviewed-by: Roman Gushchin 
Acked-by: Johannes Weiner 
Cc: Hugh Dickins 
Cc: Muchun Song 
Cc: Yosry Ahmed 
Signed-off-by: Andrew Morton

mm/page-writeback: raise wb_thresh to prevent write blocking with strictlimit

2024-11-07T04:11:17+00:00

With the strictlimit flag, wb_thresh acts as a hard limit in
balance_dirty_pages() and wb_position_ratio().  When device write
operations are inactive, wb_thresh can drop to 0, causing writes to be
blocked.  The issue occasionally occurs in fuse fs, particularly with
network backends, the write thread is blocked frequently during a period. 
To address it, this patch raises the minimum wb_thresh to a controllable
level, similar to the non-strictlimit case.

Link: https://lkml.kernel.org/r/20241023100032.62952-1-jimzhao.ai@gmail.com
Signed-off-by: Jim Zhao 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton

mm/writeback: add folio_mark_dirty_lock()

2024-11-05T10:14:32+00:00

Add a new convenience helper folio_mark_dirty_lock() that grabs the
folio lock before calling folio_mark_dirty().

Refactor set_page_dirty_lock() to directly use folio_mark_dirty_lock().

Signed-off-by: Joanne Koong 
Signed-off-by: Miklos Szeredi

mm/page-writeback.c: Fix comment of wb_domain_writeout_add()

2024-10-22T09:16:58+00:00

__bdi_writeout_inc() has undergone multiple renamings, but the comment
within the function body have not been updated accordingly. Update it
to reflect the latest wb_domain_writeout_add().

Signed-off-by: Tang Yizhou 
Link: https://lore.kernel.org/r/20241009151728.300477-3-yizhou.tang@shopee.com
Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner