linux-stable.git/samples/damon, branch linux-6.15.y

samples/damon/wsse: fix boot time enable handling

2025-08-20T16:36:27+00:00

commit 0ed1165c37277822b519f519d0982d36efc30006 upstream.

Patch series "mm/damon: fix misc bugs in DAMON modules".

From manual code review, I found below bugs in DAMON modules.

DAMON sample modules crash if those are enabled at boot time, via kernel
command line.  A similar issue was found and fixed on DAMON non-sample
modules in the past, but we didn't check that for sample modules.

DAMON non-sample modules are not setting 'enabled' parameters accordingly
when real enabling is failed.  Honggyu found and fixed[1] this type of
bugs in DAMON sample modules, and my inspection was motivated by the great
work.  Kudos to Honggyu.

Finally, DAMON_RECLIAM is mistakenly losing scheme internal status due to
misuse of damon_commit_ctx().  DAMON_LRU_SORT has a similar misuse, but
fortunately it is not causing real status loss.

Fix the bugs.  Since these are similar patterns of bugs that were found in
the past, it would be better to add tests or refactor the code, in future.


This patch (of 6):

If 'enable' parameter of the 'wsse' DAMON sample module is set at boot
time via the kernel command line, memory allocation is tried before the
slab is initialized.  As a result kernel NULL pointer dereference BUG can
happen.  Fix it by checking the initialization status.

Link: https://lkml.kernel.org/r/20250706193207.39810-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20250706193207.39810-2-sj@kernel.org
Link: https://lore.kernel.org/20250702000205.1921-1-honggyu.kim@sk.com [1]
Fixes: b757c6cfc696 ("samples/damon/wsse: start and stop DAMON as the user requests")
Signed-off-by: SeongJae Park 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

samples/damon: fix damon sample wsse for start failure

2025-07-17T16:43:52+00:00

commit f1221c8442616a6927aff836327777144545cb29 upstream.

The damon_sample_wsse_start() can fail so we must reset the "enable"
parameter to "false" again for proper rollback.

In such cases, setting Y to "enable" then N triggers the similar crash
with wsse because damon sample start failed but the "enable" stays as Y.

Link: https://lkml.kernel.org/r/20250702000205.1921-3-honggyu.kim@sk.com
Fixes: b757c6cfc696 ("samples/damon/wsse: start and stop DAMON as the user requests")
Signed-off-by: Honggyu Kim 
Reviewed-by: SeongJae Park 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

samples/damon: fix damon sample prcl for start failure

2025-07-17T16:43:52+00:00

commit d9e01c62b7a0c258a7481c083f84c766a8f5597c upstream.

Patch series "mm/damon: fix divide by zero and its samples", v3.

This series includes fixes against damon and its samples to make it safer
when damon sample starting fails.

It includes the following changes.
- fix unexpected divide by zero crash for zero size regions
- fix bugs for damon samples in case of start failures


This patch (of 4):

The damon_sample_prcl_start() can fail so we must reset the "enable"
parameter to "false" again for proper rollback.

In such cases, setting Y to "enable" then N triggers the following crash
because damon sample start failed but the "enable" stays as Y.

  [ 2441.419649] damon_sample_prcl: start
  [ 2454.146817] damon_sample_prcl: stop
  [ 2454.146862] ------------[ cut here ]------------
  [ 2454.146865] kernel BUG at mm/slub.c:546!
  [ 2454.148183] Oops: invalid opcode: 0000 [#1] SMP NOPTI
  	...
  [ 2454.167555] Call Trace:
  [ 2454.167822]  
  [ 2454.168061]  damon_destroy_ctx+0x78/0x140
  [ 2454.168454]  damon_sample_prcl_enable_store+0x8d/0xd0
  [ 2454.168932]  param_attr_store+0xa1/0x120
  [ 2454.169315]  module_attr_store+0x20/0x50
  [ 2454.169695]  sysfs_kf_write+0x72/0x90
  [ 2454.170065]  kernfs_fop_write_iter+0x150/0x1e0
  [ 2454.170491]  vfs_write+0x315/0x440
  [ 2454.170833]  ksys_write+0x69/0xf0
  [ 2454.171162]  __x64_sys_write+0x19/0x30
  [ 2454.171525]  x64_sys_call+0x18b2/0x2700
  [ 2454.171900]  do_syscall_64+0x7f/0x680
  [ 2454.172258]  ? exit_to_user_mode_loop+0xf6/0x180
  [ 2454.172694]  ? clear_bhb_loop+0x30/0x80
  [ 2454.173067]  ? clear_bhb_loop+0x30/0x80
  [ 2454.173439]  entry_SYSCALL_64_after_hwframe+0x76/0x7e

Link: https://lkml.kernel.org/r/20250702000205.1921-1-honggyu.kim@sk.com
Link: https://lkml.kernel.org/r/20250702000205.1921-2-honggyu.kim@sk.com
Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation")
Signed-off-by: Honggyu Kim 
Reviewed-by: SeongJae Park 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

samples/damon: a typo in the kconfig - sameple

2025-03-17T07:05:29+00:00

There is a typo in the Kconfig file of the damon sample module.  Correct
it: s/sameple/sample/

Link: https://lkml.kernel.org/r/20250226184204.29370-1-sj@kernel.org
Signed-off-by: Seongjun Kim 
Signed-off-by: SeongJae Park 
Reviewed-by: SeongJae Park 
Signed-off-by: Andrew Morton

samples/damon/prcl: implement schemes setup

2025-01-14T06:40:57+00:00

Implement a proactive cold memory regions reclaiming logic of prcl sample
module using DAMOS.  The logic treats memory regions that not accessed at
all for five or more seconds as cold, and reclaim those as soon as found.

Link: https://lkml.kernel.org/r/20241210215030.85675-6-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton

samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation

2025-01-14T06:40:57+00:00

DAMON is not only for monitoring of access patterns, but also for
access-aware system operations.  For the system operations, DAMON provides
a feature called DAMOS (Data Access Monitoring-based Operation Schemes). 
There is no sample API usage of DAMOS, though.  Copy the working set size
estimation sample modules with changed names of the module and symbols, to
use it as a skeleton for a sample module showing the DAMOS API usage.  The
following commit will make it proactively reclaim cold memory of the given
process, using DAMOS.

Link: https://lkml.kernel.org/r/20241210215030.85675-5-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton

samples/damon/wsse: implement working set size estimation and logging

2025-01-14T06:40:57+00:00

Implement the DAMON-based working set size estimation logic.  The logic
iterates memory regions in DAMON-generated access pattern snapshot for
every aggregation interval and get the total sum of the size of any region
having one or higher 'nr_accesses' count.  That is, it assumes any region
having one or higher 'nr_accesses' to be a part of the working set.  The
estimated value is reported to the user by printing it to the kernel log.

Link: https://lkml.kernel.org/r/20241210215030.85675-4-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton

samples/damon/wsse: start and stop DAMON as the user requests

2025-01-14T06:40:57+00:00

Start running DAMON to monitor accesses of a process that the user
specified via 'target_pid' parameter, when 'y' is passed to 'enable'
parameter.  Stop running DAMON when 'n' is passed to 'enable' parameter. 
Estimating the working set size from DAMON's monitoring results and
reporting it to the user will be implemented by the following commit.

Link: https://lkml.kernel.org/r/20241210215030.85675-3-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton

samples: add a skeleton of a sample DAMON module for working set size estimation

2025-01-14T06:40:57+00:00

Patch series "mm/damon: add sample modules".

Implement a proactive cold memory regions reclaiming logic of prcl sample
module using DAMOS.  The logic treats memory regions that not accessed at
all for five or more seconds as cold, and reclaim those as soon as found.


This patch (of 5):

Add a skeleton for a sample DAMON static module that can be used for
estimating working set size of a given process.  Note that it is a static
module since DAMON is not exporting symbols to loadable modules for now. 
It exposes two module parameters, namely 'pid' and 'enable'.  'pid' will
specify the process that the module will estimate the working set size of.
'enable' will receive whether to start or stop the estimation.  Because
this is just a skeleton, the parameters do nothing, though.  The
functionalities will be implemented by following commits.

Link: https://lkml.kernel.org/r/20241210215030.85675-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20241210215030.85675-2-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton