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<title>pm24.git/mm/damon, branch master</title>
<subtitle>Unnamed repository; edit this file 'description' to name the repository.</subtitle>
<id>https://git.kobert.dev/pm24.git/atom/mm/damon?h=master</id>
<link rel='self' href='https://git.kobert.dev/pm24.git/atom/mm/damon?h=master'/>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/'/>
<updated>2024-11-23T17:58:07Z</updated>
<entry>
<title>Merge tag 'mm-stable-2024-11-18-19-27' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm</title>
<updated>2024-11-23T17:58:07Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-11-23T17:58:07Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=5c00ff742bf5caf85f60e1c73999f99376fb865d'/>
<id>urn:sha1:5c00ff742bf5caf85f60e1c73999f99376fb865d</id>
<content type='text'>
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-&gt;index removals in mm" from Matthew Wilcox remove
   most references to page-&gt;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
  ...
</content>
</entry>
<entry>
<title>Merge tag 'timers-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2024-11-20T00:35:06Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-11-20T00:35:06Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=bf9aa14fc523d2763fc9a10672a709224e8fcaf4'/>
<id>urn:sha1:bf9aa14fc523d2763fc9a10672a709224e8fcaf4</id>
<content type='text'>
Pull timer updates from Thomas Gleixner:
 "A rather large update for timekeeping and timers:

   - The final step to get rid of auto-rearming posix-timers

     posix-timers are currently auto-rearmed by the kernel when the
     signal of the timer is ignored so that the timer signal can be
     delivered once the corresponding signal is unignored.

     This requires to throttle the timer to prevent a DoS by small
     intervals and keeps the system pointlessly out of low power states
     for no value. This is a long standing non-trivial problem due to
     the lock order of posix-timer lock and the sighand lock along with
     life time issues as the timer and the sigqueue have different life
     time rules.

     Cure this by:

       - Embedding the sigqueue into the timer struct to have the same
         life time rules. Aside of that this also avoids the lookup of
         the timer in the signal delivery and rearm path as it's just a
         always valid container_of() now.

       - Queuing ignored timer signals onto a seperate ignored list.

       - Moving queued timer signals onto the ignored list when the
         signal is switched to SIG_IGN before it could be delivered.

       - Walking the ignored list when SIG_IGN is lifted and requeue the
         signals to the actual signal lists. This allows the signal
         delivery code to rearm the timer.

     This also required to consolidate the signal delivery rules so they
     are consistent across all situations. With that all self test
     scenarios finally succeed.

   - Core infrastructure for VFS multigrain timestamping

     This is required to allow the kernel to use coarse grained time
     stamps by default and switch to fine grained time stamps when inode
     attributes are actively observed via getattr().

     These changes have been provided to the VFS tree as well, so that
     the VFS specific infrastructure could be built on top.

   - Cleanup and consolidation of the sleep() infrastructure

       - Move all sleep and timeout functions into one file

       - Rework udelay() and ndelay() into proper documented inline
         functions and replace the hardcoded magic numbers by proper
         defines.

       - Rework the fsleep() implementation to take the reality of the
         timer wheel granularity on different HZ values into account.
         Right now the boundaries are hard coded time ranges which fail
         to provide the requested accuracy on different HZ settings.

       - Update documentation for all sleep/timeout related functions
         and fix up stale documentation links all over the place

       - Fixup a few usage sites

   - Rework of timekeeping and adjtimex(2) to prepare for multiple PTP
     clocks

     A system can have multiple PTP clocks which are participating in
     seperate and independent PTP clock domains. So far the kernel only
     considers the PTP clock which is based on CLOCK TAI relevant as
     that's the clock which drives the timekeeping adjustments via the
     various user space daemons through adjtimex(2).

     The non TAI based clock domains are accessible via the file
     descriptor based posix clocks, but their usability is very limited.
     They can't be accessed fast as they always go all the way out to
     the hardware and they cannot be utilized in the kernel itself.

     As Time Sensitive Networking (TSN) gains traction it is required to
     provide fast user and kernel space access to these clocks.

     The approach taken is to utilize the timekeeping and adjtimex(2)
     infrastructure to provide this access in a similar way how the
     kernel provides access to clock MONOTONIC, REALTIME etc.

     Instead of creating a duplicated infrastructure this rework
     converts timekeeping and adjtimex(2) into generic functionality
     which operates on pointers to data structures instead of using
     static variables.

     This allows to provide time accessors and adjtimex(2) functionality
     for the independent PTP clocks in a subsequent step.

   - Consolidate hrtimer initialization

     hrtimers are set up by initializing the data structure and then
     seperately setting the callback function for historical reasons.

     That's an extra unnecessary step and makes Rust support less
     straight forward than it should be.

     Provide a new set of hrtimer_setup*() functions and convert the
     core code and a few usage sites of the less frequently used
     interfaces over.

     The bulk of the htimer_init() to hrtimer_setup() conversion is
     already prepared and scheduled for the next merge window.

   - Drivers:

       - Ensure that the global timekeeping clocksource is utilizing the
         cluster 0 timer on MIPS multi-cluster systems.

         Otherwise CPUs on different clusters use their cluster specific
         clocksource which is not guaranteed to be synchronized with
         other clusters.

       - Mostly boring cleanups, fixes, improvements and code movement"

* tag 'timers-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (140 commits)
  posix-timers: Fix spurious warning on double enqueue versus do_exit()
  clocksource/drivers/arm_arch_timer: Use of_property_present() for non-boolean properties
  clocksource/drivers/gpx: Remove redundant casts
  clocksource/drivers/timer-ti-dm: Fix child node refcount handling
  dt-bindings: timer: actions,owl-timer: convert to YAML
  clocksource/drivers/ralink: Add Ralink System Tick Counter driver
  clocksource/drivers/mips-gic-timer: Always use cluster 0 counter as clocksource
  clocksource/drivers/timer-ti-dm: Don't fail probe if int not found
  clocksource/drivers:sp804: Make user selectable
  clocksource/drivers/dw_apb: Remove unused dw_apb_clockevent functions
  hrtimers: Delete hrtimer_init_on_stack()
  alarmtimer: Switch to use hrtimer_setup() and hrtimer_setup_on_stack()
  io_uring: Switch to use hrtimer_setup_on_stack()
  sched/idle: Switch to use hrtimer_setup_on_stack()
  hrtimers: Delete hrtimer_init_sleeper_on_stack()
  wait: Switch to use hrtimer_setup_sleeper_on_stack()
  timers: Switch to use hrtimer_setup_sleeper_on_stack()
  net: pktgen: Switch to use hrtimer_setup_sleeper_on_stack()
  futex: Switch to use hrtimer_setup_sleeper_on_stack()
  fs/aio: Switch to use hrtimer_setup_sleeper_on_stack()
  ...
</content>
</entry>
<entry>
<title>Merge branch 'mm-hotfixes-stable' into mm-stable</title>
<updated>2024-11-11T08:04:10Z</updated>
<author>
<name>Andrew Morton</name>
<email>akpm@linux-foundation.org</email>
</author>
<published>2024-11-11T08:04:10Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=2ec0859039ecddc95f5d94c134d01aa639a49622'/>
<id>urn:sha1:2ec0859039ecddc95f5d94c134d01aa639a49622</id>
<content type='text'>
Pick up e7ac4daeed91 ("mm: count zeromap read and set for swapout and
swapin") in order to move

mm: define obj_cgroup_get() if CONFIG_MEMCG is not defined
mm: zswap: modify zswap_compress() to accept a page instead of a folio
mm: zswap: rename zswap_pool_get() to zswap_pool_tryget()
mm: zswap: modify zswap_stored_pages to be atomic_long_t
mm: zswap: support large folios in zswap_store()
mm: swap: count successful large folio zswap stores in hugepage zswpout stats
mm: zswap: zswap_store_page() will initialize entry after adding to xarray.
mm: add per-order mTHP swpin counters

from mm-unstable into mm-stable.
</content>
</entry>
<entry>
<title>mm/damon/tests/dbgfs-kunit: fix the header double inclusion guarding ifdef comment</title>
<updated>2024-11-07T22:38:08Z</updated>
<author>
<name>SeongJae Park</name>
<email>sj@kernel.org</email>
</author>
<published>2024-10-28T23:30:58Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=73da523802eafafe7e55a5e8a8bc8ee3f5cf3b9b'/>
<id>urn:sha1:73da523802eafafe7e55a5e8a8bc8ee3f5cf3b9b</id>
<content type='text'>
Closing part of double inclusion guarding macro for dbgfs-kunit.h was
copy-pasted from somewhere (maybe before the initial mainline merge of
DAMON), and not properly updated.  Fix it.

Link: https://lkml.kernel.org/r/20241028233058.283381-7-sj@kernel.org
Fixes: 17ccae8bb5c9 ("mm/damon: add kunit tests")
Signed-off-by: SeongJae Park &lt;sj@kernel.org&gt;
Cc: Andrew Paniakin &lt;apanyaki@amazon.com&gt;
Cc: Brendan Higgins &lt;brendan.higgins@linux.dev&gt;
Cc: David Gow &lt;davidgow@google.com&gt;
Cc: Shuah Khan &lt;shuah@kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/damon/Kconfig: update DBGFS_KUNIT prompt copy for SYSFS_KUNIT</title>
<updated>2024-11-07T22:38:08Z</updated>
<author>
<name>SeongJae Park</name>
<email>sj@kernel.org</email>
</author>
<published>2024-10-28T23:30:57Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=12d021659c7aa5059835e671e57c4a163a64d2e9'/>
<id>urn:sha1:12d021659c7aa5059835e671e57c4a163a64d2e9</id>
<content type='text'>
CONFIG_DAMON_SYSFS_KUNIT_TEST prompt is copied from that for DAMON debugfs
interface kunit tests, and not correctly updated.  Fix it.

Link: https://lkml.kernel.org/r/20241028233058.283381-6-sj@kernel.org
Fixes: b8ee5575f763 ("mm/damon/sysfs-test: add a unit test for damon_sysfs_set_targets()")
Signed-off-by: SeongJae Park &lt;sj@kernel.org&gt;
Cc: Andrew Paniakin &lt;apanyaki@amazon.com&gt;
Cc: Brendan Higgins &lt;brendan.higgins@linux.dev&gt;
Cc: David Gow &lt;davidgow@google.com&gt;
Cc: Shuah Khan &lt;shuah@kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/damon/core: avoid overflow in damon_feed_loop_next_input()</title>
<updated>2024-11-07T22:14:59Z</updated>
<author>
<name>SeongJae Park</name>
<email>sj@kernel.org</email>
</author>
<published>2024-10-31T16:12:03Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=4401e9d10ab0281a520b9f8c220f30f60b5c248f'/>
<id>urn:sha1:4401e9d10ab0281a520b9f8c220f30f60b5c248f</id>
<content type='text'>
damon_feed_loop_next_input() is inefficient and fragile to overflows. 
Specifically, 'score_goal_diff_bp' calculation can overflow when 'score'
is high.  The calculation is actually unnecessary at all because 'goal' is
a constant of value 10,000.  Calculation of 'compensation' is again
fragile to overflow.  Final calculation of return value for under-achiving
case is again fragile to overflow when the current score is
under-achieving the target.

Add two corner cases handling at the beginning of the function to make the
body easier to read, and rewrite the body of the function to avoid
overflows and the unnecessary bp value calcuation.

Link: https://lkml.kernel.org/r/20241031161203.47751-1-sj@kernel.org
Fixes: 9294a037c015 ("mm/damon/core: implement goal-oriented feedback-driven quota auto-tuning")
Signed-off-by: SeongJae Park &lt;sj@kernel.org&gt;
Reported-by: Guenter Roeck &lt;linux@roeck-us.net&gt;
Closes: https://lore.kernel.org/944f3d5b-9177-48e7-8ec9-7f1331a3fea3@roeck-us.net
Tested-by: Guenter Roeck &lt;linux@roeck-us.net&gt;
Cc: &lt;stable@vger.kernel.org&gt;	[6.8.x]
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/damon/core: handle zero schemes apply interval</title>
<updated>2024-11-07T22:14:58Z</updated>
<author>
<name>SeongJae Park</name>
<email>sj@kernel.org</email>
</author>
<published>2024-10-31T18:37:57Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=8e7bde615f634a82a44b1f3d293c049fd3ef9ca9'/>
<id>urn:sha1:8e7bde615f634a82a44b1f3d293c049fd3ef9ca9</id>
<content type='text'>
DAMON's logics to determine if this is the time to apply damos schemes
assumes next_apply_sis is always set larger than current
passed_sample_intervals.  And therefore assume continuously incrementing
passed_sample_intervals will make it reaches to the next_apply_sis in
future.  The logic hence does apply the scheme and update next_apply_sis
only if passed_sample_intervals is same to next_apply_sis.

If Schemes apply interval is set as zero, however, next_apply_sis is set
same to current passed_sample_intervals, respectively.  And
passed_sample_intervals is incremented before doing the next_apply_sis
check.  Hence, next_apply_sis becomes larger than next_apply_sis, and the
logic says it is not the time to apply schemes and update next_apply_sis. 
In other words, DAMON stops applying schemes until passed_sample_intervals
overflows.

Based on the documents and the common sense, a reasonable behavior for
such inputs would be applying the schemes for every sampling interval. 
Handle the case by removing the assumption.

Link: https://lkml.kernel.org/r/20241031183757.49610-3-sj@kernel.org
Fixes: 42f994b71404 ("mm/damon/core: implement scheme-specific apply interval")
Signed-off-by: SeongJae Park &lt;sj@kernel.org&gt;
Cc: &lt;stable@vger.kernel.org&gt;	[6.7.x]
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/damon/core: handle zero {aggregation,ops_update} intervals</title>
<updated>2024-11-07T22:14:58Z</updated>
<author>
<name>SeongJae Park</name>
<email>sj@kernel.org</email>
</author>
<published>2024-10-31T18:37:56Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=3488af0970445ff5532c7e8dc5e6456b877aee5e'/>
<id>urn:sha1:3488af0970445ff5532c7e8dc5e6456b877aee5e</id>
<content type='text'>
Patch series "mm/damon/core: fix handling of zero non-sampling intervals".

DAMON's internal intervals accounting logic is not correctly handling
non-sampling intervals of zero values for a wrong assumption.  This could
cause unexpected monitoring behavior, and even result in infinite hang of
DAMON sysfs interface user threads in case of zero aggregation interval. 
Fix those by updating the intervals accounting logic.  For details of the
root case and solutions, please refer to commit messages of fixes.


This patch (of 2):

DAMON's logics to determine if this is the time to do aggregation and ops
update assumes next_{aggregation,ops_update}_sis are always set larger
than current passed_sample_intervals.  And therefore it further assumes
continuously incrementing passed_sample_intervals every sampling interval
will make it reaches to the next_{aggregation,ops_update}_sis in future. 
The logic therefore make the action and update
next_{aggregation,ops_updaste}_sis only if passed_sample_intervals is same
to the counts, respectively.

If Aggregation interval or Ops update interval are zero, however,
next_aggregation_sis or next_ops_update_sis are set same to current
passed_sample_intervals, respectively.  And passed_sample_intervals is
incremented before doing the next_{aggregation,ops_update}_sis check. 
Hence, passed_sample_intervals becomes larger than
next_{aggregation,ops_update}_sis, and the logic says it is not the time
to do the action and update next_{aggregation,ops_update}_sis forever,
until an overflow happens.  In other words, DAMON stops doing aggregations
or ops updates effectively forever, and users cannot get monitoring
results.

Based on the documents and the common sense, a reasonable behavior for
such inputs is doing an aggregation and an ops update for every sampling
interval.  Handle the case by removing the assumption.

Note that this could incur particular real issue for DAMON sysfs interface
users, in case of zero Aggregation interval.  When user starts DAMON with
zero Aggregation interval and asks online DAMON parameter tuning via DAMON
sysfs interface, the request is handled by the aggregation callback. 
Until the callback finishes the work, the user who requested the online
tuning just waits.  Hence, the user will be stuck until the
passed_sample_intervals overflows.

Link: https://lkml.kernel.org/r/20241031183757.49610-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20241031183757.49610-2-sj@kernel.org
Fixes: 4472edf63d66 ("mm/damon/core: use number of passed access sampling as a timer")
Signed-off-by: SeongJae Park &lt;sj@kernel.org&gt;
Cc: &lt;stable@vger.kernel.org&gt;	[6.7.x]
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/damon/vaddr: add 'nr_piece == 1' check in damon_va_evenly_split_region()</title>
<updated>2024-11-07T04:11:18Z</updated>
<author>
<name>Zheng Yejian</name>
<email>zhengyejian@huaweicloud.com</email>
</author>
<published>2024-10-22T08:39:27Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=477327e10639a1ec5698847030b494dc75de33e4'/>
<id>urn:sha1:477327e10639a1ec5698847030b494dc75de33e4</id>
<content type='text'>
As discussed in [1], damon_va_evenly_split_region() is called to
size-evenly split a region into 'nr_pieces' small regions,
when nr_pieces == 1, no actual split is required. Check that case
for better code readability and add a simple kunit testcase.

[1] https://lore.kernel.org/all/20241021163316.12443-1-sj@kernel.org/

Link: https://lkml.kernel.org/r/20241022083927.3592237-3-zhengyejian@huaweicloud.com
Signed-off-by: Zheng Yejian &lt;zhengyejian@huaweicloud.com&gt;
Reviewed-by: SeongJae Park &lt;sj@kernel.org&gt;
Cc: Fernand Sieber &lt;sieberf@amazon.com&gt;
Cc: Leonard Foerster &lt;foersleo@amazon.de&gt;
Cc: Shakeel Butt &lt;shakeel.butt@linux.dev&gt;
Cc: Ye Weihua &lt;yeweihua4@huawei.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm/damon/vaddr: fix issue in damon_va_evenly_split_region()</title>
<updated>2024-11-07T04:11:18Z</updated>
<author>
<name>Zheng Yejian</name>
<email>zhengyejian@huaweicloud.com</email>
</author>
<published>2024-10-22T08:39:26Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=f3c7a1ede435e2e45177d7a490a85fb0a0ec96d1'/>
<id>urn:sha1:f3c7a1ede435e2e45177d7a490a85fb0a0ec96d1</id>
<content type='text'>
Patch series "mm/damon/vaddr: Fix issue in
damon_va_evenly_split_region()".  v2.

According to the logic of damon_va_evenly_split_region(), currently
following split case would not meet the expectation:

  Suppose DAMON_MIN_REGION=0x1000,
  Case: Split [0x0, 0x3000) into 2 pieces, then the result would be
        acutually 3 regions:
          [0x0, 0x1000), [0x1000, 0x2000), [0x2000, 0x3000)
        but NOT the expected 2 regions:
          [0x0, 0x1000), [0x1000, 0x3000) !!!

The root cause is that when calculating size of each split piece in
damon_va_evenly_split_region():

  `sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, DAMON_MIN_REGION);`

both the dividing and the ALIGN_DOWN may cause loss of precision, then
each time split one piece of size 'sz_piece' from origin 'start' to 'end'
would cause more pieces are split out than expected!!!

To fix it, count for each piece split and make sure no more than
'nr_pieces'.  In addition, add above case into damon_test_split_evenly().

And add 'nr_piece == 1' check in damon_va_evenly_split_region() for better
code readability and add a corresponding kunit testcase.


This patch (of 2):

According to the logic of damon_va_evenly_split_region(), currently
following split case would not meet the expectation:

  Suppose DAMON_MIN_REGION=0x1000,
  Case: Split [0x0, 0x3000) into 2 pieces, then the result would be
        acutually 3 regions:
          [0x0, 0x1000), [0x1000, 0x2000), [0x2000, 0x3000)
        but NOT the expected 2 regions:
          [0x0, 0x1000), [0x1000, 0x3000) !!!

The root cause is that when calculating size of each split piece in
damon_va_evenly_split_region():

  `sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, DAMON_MIN_REGION);`

both the dividing and the ALIGN_DOWN may cause loss of precision,
then each time split one piece of size 'sz_piece' from origin 'start' to
'end' would cause more pieces are split out than expected!!!

To fix it, count for each piece split and make sure no more than
'nr_pieces'. In addition, add above case into damon_test_split_evenly().

After this patch, damon-operations test passed:

 # ./tools/testing/kunit/kunit.py run damon-operations
 [...]
 ============== damon-operations (6 subtests) ===============
 [PASSED] damon_test_three_regions_in_vmas
 [PASSED] damon_test_apply_three_regions1
 [PASSED] damon_test_apply_three_regions2
 [PASSED] damon_test_apply_three_regions3
 [PASSED] damon_test_apply_three_regions4
 [PASSED] damon_test_split_evenly
 ================ [PASSED] damon-operations =================

Link: https://lkml.kernel.org/r/20241022083927.3592237-1-zhengyejian@huaweicloud.com
Link: https://lkml.kernel.org/r/20241022083927.3592237-2-zhengyejian@huaweicloud.com
Fixes: 3f49584b262c ("mm/damon: implement primitives for the virtual memory address spaces")
Signed-off-by: Zheng Yejian &lt;zhengyejian@huaweicloud.com&gt;
Reviewed-by: SeongJae Park &lt;sj@kernel.org&gt;
Cc: Fernand Sieber &lt;sieberf@amazon.com&gt;
Cc: Leonard Foerster &lt;foersleo@amazon.de&gt;
Cc: Shakeel Butt &lt;shakeel.butt@linux.dev&gt;
Cc: Ye Weihua &lt;yeweihua4@huawei.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
</content>
</entry>
</feed>
