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damon_call() failure was causing the context to be stopped, but
asynchronously by the kdamond thread. To handle the race, the caller had
to stop the context. damon_call() is updated to do the stop on its own.
Remove the damon_stop() call from the damon_call() error handling.
Link: https://lore.kernel.org/20260706140628.87414-11-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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damon_sample_wsse_start() calls damon_call() right after damon_start() is
succeeded. The kdamond that has started by the damon_start() could be
terminated by itself before or in the middle of the damon_call()
execution. There could be multiple reasons for such a stop including
monitoring target process termination and kdamond_fn() internal memory
allocation failures. In the case, damon_call() will fail and return an
error without cleaning up the DAMON context object. The
damon_sample_wsse_start() caller assumes it would clean up the object,
though. When the user requests to start DAMON again,
damon_sample_wsse_start() is called again, allocates a new DAMON context
object and overwrites the pointer for the previous object. As a result,
the previous context object is leaked.
Safely stop the kdamond and deallocate the context object when the failure
is returned. Note that the kdamond should be stopped first, because
damon_call() failure means not complete termination of the kdamond but
only the fact that the termination process has started.
The user impact shouldn't be that significant because the race is not easy
to happen, and only up to one DAMON context object can be leaked per race.
The issue was discovered [1] by Sashiko.
Link: https://lore.kernel.org/20260628215447.96166-6-sj@kernel.org
Link: https://lore.kernel.org/20260610034828.4632-1-sj@kernel.org [1]
Fixes: cc9c1b8c205b ("samples/damon/wsse: use damon_call() repeat mode instead of damon_callback")
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Cc: <stable@vger.kernel.org> # 6.17.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "samples/damon: handle damon_{start,stop}() failures".
All DAMON sample modules are not correctly handling failures from
damon_start(). Among those, mtier also has an additional problem for
handling of damon_stop() failures. wsse and prcl also have a problem in
their damon_call() failure handling. As a result, memory leaks, next
DAMON operation disruptions, and use-after-free can happen. Fix those.
Note that only the damon_start() failure caused issues can reliably be
reproduced. Reproducing those issues require the admin permission,
though.
This patch (of 6):
damon_sample_wsse_start() callers assume it will clean up resources when
it fails. And the function does the cleanup for context buildup failures.
However, it is not doing the cleanup for damon_start() failure. As a
result, when damon_start() fails, it leaks the memory for DAMON context.
Free the context in case of the failure to fix the issues.
Note that the issue can reliably be reproduced because the module calls
damon_start() in the exclusive mode. For example,
$ sudo damo start
$ echo $$ | sudo tee /sys/module/damon_sample_wsse/parameters/target_pid
$ echo Y | sudo tee /sys/module/damon_sample_wsse/parameters/enabled
$ sudo cat /proc/allocinfo | grep damon_new_ctx
Because the first command is running another DAMON instance, the third
command fails the damon_start() call because the new DAMON instance cannot
exclusively run. And without this fix, by repeating the third and the
fourth commands above, we can show the memory consumption is only
increasing due to the leaks. It requires the sudo permission though.
The issue was discovered [1] by Sashiko.
Link: https://lore.kernel.org/20260628215447.96166-2-sj@kernel.org
Link: https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org [1]
Fixes: b757c6cfc696 ("samples/damon/wsse: start and stop DAMON as the user requests")
Signed-off-by: SJ Park <sj@kernel.org>
Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev>
Cc: <stable@vger.kernel.org> # 6.14.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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damon_sample_wsse is assuming DAMON is ready to use in module_init time,
and uses its own hack to see if it is the time. Use damon_initialized(),
which is a way for seeing if DAMON is ready to be used that is more
reliable and better to maintain instead of the hack.
Link: https://lkml.kernel.org/r/20250916033511.116366-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "samples/damon: fix boot time enable handling fixup merge
mistakes".
First three patches of the patch series "mm/damon: fix misc bugs in DAMON
modules" [1] were trying to fix boot time DAMON sample modules enabling
issues. The issues are the modules can crash if those are enabled before
DAMON is enabled, like using boot time parameter options. The three
patches were fixing the issues by avoiding starting DAMON before the
module initialization phase.
However, probably by a mistake during a merge, only half of the change is
merged, and the part for avoiding the starting of DAMON before the module
initialized is missed. So the problem is not solved and thus the modules
can still crash if enabled before DAMON is initialized. Fix those by
applying the unmerged parts again.
Note that the broken commits are merged into 6.17-rc1, but also backported
to relevant stable kernels. So this series also needs to be merged into
the stable kernels. Hence Cc-ing stable@.
This patch (of 3):
Commit 0ed1165c3727 ("samples/damon/wsse: fix boot time enable handling")
is somehow incompletely applying the origin patch [2]. It is missing the
part that avoids starting DAMON before module initialization. Probably a
mistake during a merge has happened. Fix it by applying the missed part
again.
Link: https://lkml.kernel.org/r/20250909022238.2989-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20250909022238.2989-2-sj@kernel.org
Link: https://lkml.kernel.org/r/20250706193207.39810-1-sj@kernel.org [1]
Link: https://lore.kernel.org/20250706193207.39810-2-sj@kernel.org [2]
Fixes: 0ed1165c3727 ("samples/damon/wsse: fix boot time enable handling")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Implement cleanup_target() callback for [f]vaddr, which calls put_pid()
for each target that will be destroyed. Also remove redundant put_pid()
calls in core, sysfs and sample modules, which were required to be done
redundantly due to the lack of such self cleanup in vaddr.
Link: https://lkml.kernel.org/r/20250712195016.151108-11-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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wsse uses damon_callback for periodically reading DAMON internal data.
Use its alternative, damon_call() repeat mode.
Link: https://lkml.kernel.org/r/20250712195016.151108-8-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The damon_{lru_sort,reclaim,stat} kernel modules use "enabled" parameter
knobs as follows.
/sys/module/damon_lru_sort/parameters/enabled
/sys/module/damon_reclaim/parameters/enabled
/sys/module/damon_stat/parameters/enabled
However, other sample modules of damon use "enable" parameter knobs so
it'd be better to rename them from "enable" to "enabled" to keep the
consistency with other damon modules.
Before:
/sys/module/damon_sample_wsse/parameters/enable
/sys/module/damon_sample_prcl/parameters/enable
/sys/module/damon_sample_mtier/parameters/enable
After:
/sys/module/damon_sample_wsse/parameters/enabled
/sys/module/damon_sample_prcl/parameters/enabled
/sys/module/damon_sample_mtier/parameters/enabled
There is no functional changes in this patch.
Link: https://lkml.kernel.org/r/20250707024548.1964-1-honggyu.kim@sk.com
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "mm/damon: misc cleanups".
Yet another round of miscellaneous DAMON cleanups.
This patch (of 6):
DAMON sample module, wsse has its name 'wsse'. It could conflict with
future modules, and not very easy to identify it by name. Use a prefix,
"damon_sample_" for the name.
Note that this could break users if they depend on the old name. But it
is just a sample, so no such usage is expected, or known. Even if such
usage exists, updating it for the new name should be straightforward.
Link: https://lkml.kernel.org/r/20250705175000.56259-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20250705175000.56259-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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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 <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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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 <honggyu.kim@sk.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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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 <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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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 <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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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 <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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