linux.git/mm/backing-dev.c, branch v6.6.131

blk-wbt: Fix detection of dirty-throttled tasks

2024-02-23T08:25:16+00:00

commit f814bdda774c183b0cc15ec8f3b6e7c6f4527ba5 upstream.

The detection of dirty-throttled tasks in blk-wbt has been subtly broken
since its beginning in 2016. Namely if we are doing cgroup writeback and
the throttled task is not in the root cgroup, balance_dirty_pages() will
set dirty_sleep for the non-root bdi_writeback structure. However
blk-wbt checks dirty_sleep only in the root cgroup bdi_writeback
structure. Thus detection of recently throttled tasks is not working in
this case (we noticed this when we switched to cgroup v2 and suddently
writeback was slow).

Since blk-wbt has no easy way to get to proper bdi_writeback and
furthermore its intention has always been to work on the whole device
rather than on individual cgroups, just move the dirty_sleep timestamp
from bdi_writeback to backing_dev_info. That fixes the checking for
recently throttled task and saves memory for everybody as a bonus.

CC: stable@vger.kernel.org
Fixes: b57d74aff9ab ("writeback: track if we're sleeping on progress in balance_dirty_pages()")
Signed-off-by: Jan Kara 
Link: https://lore.kernel.org/r/20240123175826.21452-1-jack@suse.cz
[axboe: fixup indentation errors]
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

writeback: remove redundant checks for root memcg

2023-08-21T20:37:48+00:00

The check for root memcg will be done in wb_get_lookup(), so remove the
redundant one to simplify the code.

Link: https://lkml.kernel.org/r/20230808084431.1632934-1-alexjlzheng@tencent.com
Signed-off-by: Jinliang Zheng 
Signed-off-by: Andrew Morton

mm: remove redundant K() macro definition

2023-08-21T20:37:44+00:00

Patch series "cleanup with helper macro K()".

Use helper macro K() to improve code readability.  No functional
modification involved.  Remove redundant K() macro definition.


This patch (of 7):

Since commit eb8589b4f8c1 ("mm: move mem_init_print_info() to mm_init.c"),
the K() macro definition has been moved to mm/internal.h.  Therefore, the
definitions in mm/memcontrol.c, mm/backing-dev.c and mm/oom_kill.c are
redundant.  Drop redundant definitions.

[akpm@linux-foundation.org: oom_kill.c: remove "#undef K", per Kefeng]
Link: https://lkml.kernel.org/r/20230804012559.2617515-1-zhangpeng362@huawei.com
Link: https://lkml.kernel.org/r/20230804012559.2617515-2-zhangpeng362@huawei.com
Signed-off-by: ZhangPeng 
Reviewed-by: Matthew Wilcox (Oracle) 
Reviewed-by: David Hildenbrand 
Cc: Kefeng Wang 
Cc: Nanyong Sun 
Signed-off-by: Andrew Morton

mm: backing-dev: make bdi_class a static const structure

2023-06-23T23:59:27+00:00

Now that the driver core allows for struct class to be in read-only
memory, move the bdi_class structure to be declared at build time placing
it into read-only memory, instead of having to be dynamically allocated at
load time.

Link: https://lkml.kernel.org/r/20230620183314.682822-2-gregkh@linuxfoundation.org
Signed-off-by: Ivan Orlov 
Signed-off-by: Greg Kroah-Hartman 
Suggested-by: Greg Kroah-Hartman 
Cc: Jens Axboe 
Cc: Christoph Hellwig 
Signed-off-by: Andrew Morton

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

2023-04-28T02:42:02+00:00

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
...

Merge tag 'driver-core-6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

2023-04-27T18:53:57+00:00

Pull driver core updates from Greg KH:
 "Here is the large set of driver core changes for 6.4-rc1.

  Once again, a busy development cycle, with lots of changes happening
  in the driver core in the quest to be able to move "struct bus" and
  "struct class" into read-only memory, a task now complete with these
  changes.

  This will make the future rust interactions with the driver core more
  "provably correct" as well as providing more obvious lifetime rules
  for all busses and classes in the kernel.

  The changes required for this did touch many individual classes and
  busses as many callbacks were changed to take const * parameters
  instead. All of these changes have been submitted to the various
  subsystem maintainers, giving them plenty of time to review, and most
  of them actually did so.

  Other than those changes, included in here are a small set of other
  things:

   - kobject logging improvements

   - cacheinfo improvements and updates

   - obligatory fw_devlink updates and fixes

   - documentation updates

   - device property cleanups and const * changes

   - firwmare loader dependency fixes.

  All of these have been in linux-next for a while with no reported
  problems"

* tag 'driver-core-6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (120 commits)
  device property: make device_property functions take const device *
  driver core: update comments in device_rename()
  driver core: Don't require dynamic_debug for initcall_debug probe timing
  firmware_loader: rework crypto dependencies
  firmware_loader: Strip off \n from customized path
  zram: fix up permission for the hot_add sysfs file
  cacheinfo: Add use_arch[|_cache]_info field/function
  arch_topology: Remove early cacheinfo error message if -ENOENT
  cacheinfo: Check cache properties are present in DT
  cacheinfo: Check sib_leaf in cache_leaves_are_shared()
  cacheinfo: Allow early level detection when DT/ACPI info is missing/broken
  cacheinfo: Add arm64 early level initializer implementation
  cacheinfo: Add arch specific early level initializer
  tty: make tty_class a static const structure
  driver core: class: remove struct class_interface * from callbacks
  driver core: class: mark the struct class in struct class_interface constant
  driver core: class: make class_register() take a const *
  driver core: class: mark class_release() as taking a const *
  driver core: remove incorrect comment for device_create*
  MIPS: vpe-cmp: remove module owner pointer from struct class usage.
  ...

mm: backing-dev: set variables dev_attr_min,max_bytes storage-class-specifier to static

2023-04-18T23:29:56+00:00

smatch reports
mm/backing-dev.c:266:1: warning: symbol
  'dev_attr_min_bytes' was not declared. Should it be static?
mm/backing-dev.c:294:1: warning: symbol
  'dev_attr_max_bytes' was not declared. Should it be static?

These variables are only used in one file so should be static.

Link: https://lkml.kernel.org/r/20230408141609.2703647-1-trix@redhat.com
Signed-off-by: Tom Rix 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Andrew Morton

writeback, cgroup: fix null-ptr-deref write in bdi_split_work_to_wbs

2023-04-16T17:41:26+00:00

KASAN report null-ptr-deref:
==================================================================
BUG: KASAN: null-ptr-deref in bdi_split_work_to_wbs+0x5c5/0x7b0
Write of size 8 at addr 0000000000000000 by task sync/943
CPU: 5 PID: 943 Comm: sync Tainted: 6.3.0-rc5-next-20230406-dirty #461
Call Trace:
 
 dump_stack_lvl+0x7f/0xc0
 print_report+0x2ba/0x340
 kasan_report+0xc4/0x120
 kasan_check_range+0x1b7/0x2e0
 __kasan_check_write+0x24/0x40
 bdi_split_work_to_wbs+0x5c5/0x7b0
 sync_inodes_sb+0x195/0x630
 sync_inodes_one_sb+0x3a/0x50
 iterate_supers+0x106/0x1b0
 ksys_sync+0x98/0x160
[...]
==================================================================

The race that causes the above issue is as follows:

           cpu1                     cpu2
-------------------------|-------------------------
inode_switch_wbs
 INIT_WORK(&isw->work, inode_switch_wbs_work_fn)
 queue_rcu_work(isw_wq, &isw->work)
 // queue_work async
  inode_switch_wbs_work_fn
   wb_put_many(old_wb, nr_switched)
    percpu_ref_put_many
     ref->data->release(ref)
     cgwb_release
      queue_work(cgwb_release_wq, &wb->release_work)
      // queue_work async
       &wb->release_work
       cgwb_release_workfn
                            ksys_sync
                             iterate_supers
                              sync_inodes_one_sb
                               sync_inodes_sb
                                bdi_split_work_to_wbs
                                 kmalloc(sizeof(*work), GFP_ATOMIC)
                                 // alloc memory failed
        percpu_ref_exit
         ref->data = NULL
         kfree(data)
                                 wb_get(wb)
                                  percpu_ref_get(&wb->refcnt)
                                   percpu_ref_get_many(ref, 1)
                                    atomic_long_add(nr, &ref->data->count)
                                     atomic64_add(i, v)
                                     // trigger null-ptr-deref

bdi_split_work_to_wbs() traverses &bdi->wb_list to split work into all
wbs.  If the allocation of new work fails, the on-stack fallback will be
used and the reference count of the current wb is increased afterwards. 
If cgroup writeback membership switches occur before getting the reference
count and the current wb is released as old_wd, then calling wb_get() or
wb_put() will trigger the null pointer dereference above.

This issue was introduced in v4.3-rc7 (see fix tag1).  Both
sync_inodes_sb() and __writeback_inodes_sb_nr() calls to
bdi_split_work_to_wbs() can trigger this issue.  For scenarios called via
sync_inodes_sb(), originally commit 7fc5854f8c6e ("writeback: synchronize
sync(2) against cgroup writeback membership switches") reduced the
possibility of the issue by adding wb_switch_rwsem, but in v5.14-rc1 (see
fix tag2) removed the "inode_io_list_del_locked(inode, old_wb)" from
inode_switch_wbs_work_fn() so that wb->state contains WB_has_dirty_io,
thus old_wb is not skipped when traversing wbs in bdi_split_work_to_wbs(),
and the issue becomes easily reproducible again.

To solve this problem, percpu_ref_exit() is called under RCU protection to
avoid race between cgwb_release_workfn() and bdi_split_work_to_wbs(). 
Moreover, replace wb_get() with wb_tryget() in bdi_split_work_to_wbs(),
and skip the current wb if wb_tryget() fails because the wb has already
been shutdown.

Link: https://lkml.kernel.org/r/20230410130826.1492525-1-libaokun1@huawei.com
Fixes: b817525a4a80 ("writeback: bdi_writeback iteration must not skip dying ones")
Signed-off-by: Baokun Li 
Reviewed-by: Jan Kara 
Acked-by: Tejun Heo 
Cc: Alexander Viro 
Cc: Andreas Dilger 
Cc: Christian Brauner 
Cc: Dennis Zhou 
Cc: Hou Tao 
Cc: yangerkun 
Cc: Zhang Yi 
Cc: Jens Axboe 
Cc: 
Signed-off-by: Andrew Morton

driver core: class: remove module * from class_create()

2023-03-17T14:16:33+00:00

The module pointer in class_create() never actually did anything, and it
shouldn't have been requred to be set as a parameter even if it did
something.  So just remove it and fix up all callers of the function in
the kernel tree at the same time.

Cc: "Rafael J. Wysocki" 
Acked-by: Benjamin Tissoires 
Link: https://lore.kernel.org/r/20230313181843.1207845-4-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman

mm: add /sys/class/bdi//min_ratio_fine knob

2022-11-30T23:59:06+00:00

This adds the min_ratio_fine knob. The knob specifies the values not
based on 1 of 100, but instead 1 per million.

Link: https://lkml.kernel.org/r/20221119005215.3052436-20-shr@devkernel.io
Signed-off-by: Stefan Roesch 
Cc: Chris Mason 
Cc: Jens Axboe 
Signed-off-by: Andrew Morton