kernel/git/stable/linux.git/samples/damon/prcl.c, branch linux-7.2.y

samples/damon/prcl: stop and free damon ctx when damon_call() fails

2026-09-11T09:50:49+00:00

commit a73fa45d3f0f42c446ae55c5799e3d5ef044cd5d upstream. damon_sample_prcl_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_prcl_start() caller assumes it would clean up the object, though. When the user requests to start DAMON again, damon_sample_prcl_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/20260628215447.96166-7-sj@kernel.org Link: https://lore.kernel.org/20260610035214.4850-1-sj@kernel.org [1] Fixes: a6c33f1054e3 ("samples/damon/prcl: use damon_call() repeat mode instead of damon_callback") Signed-off-by: SJ Park Reviewed-by: Zenghui Yu Cc: # 6.17.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

samples/damon/prcl: handle damon_start() failure

2026-09-11T09:50:49+00:00

commit 8b724349229bb6ebbf781178be011ba9bc2cca57 upstream. damon_sample_prcl_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_prcl/parameters/target_pid $ echo Y | sudo tee /sys/module/damon_sample_prcl/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/20260628215447.96166-3-sj@kernel.org Link: https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org [1] Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation") Signed-off-by: SJ Park Reviewed-by: Zenghui Yu Cc: # 6.14.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

samples/damon/prcl: use damon_initialized()

2025-09-21T21:22:38+00:00

damon_sample_prcl 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/20250916033511.116366-7-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon/prcl: avoid starting DAMON before initialization

2025-09-13T20:05:37+00:00

Commit 2780505ec2b4 ("samples/damon/prcl: fix boot time enable crash") is somehow incompletely applying the origin patch [1]. 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/20250909022238.2989-3-sj@kernel.org Link: https://lore.kernel.org/20250706193207.39810-3-sj@kernel.org [1] Fixes: 2780505ec2b4 ("samples/damon/prcl: fix boot time enable crash") Signed-off-by: SeongJae Park Cc: Signed-off-by: Andrew Morton

mm/damon/vaddr: put pid in cleanup_target()

2025-07-20T01:59:56+00:00

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 Signed-off-by: Andrew Morton

samples/damon/prcl: use damon_call() repeat mode instead of damon_callback

2025-07-20T01:59:55+00:00

prcl uses damon_callback for periodically reading DAMON internal data. Use its alternative, damon_call() repeat mode. Link: https://lkml.kernel.org/r/20250712195016.151108-7-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon: change enable parameters to enabled

2025-07-20T01:59:47+00:00

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 Reviewed-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon/prcl: rename to have damon_sample_ prefix

2025-07-20T01:59:43+00:00

DAMON sample module, prcl has its name 'prcl'. 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/20250705175000.56259-3-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon/prcl: fix boot time enable crash

2025-07-13T23:38:34+00:00

If 'enable' parameter of the 'prcl' 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/20250706193207.39810-3-sj@kernel.org Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation") Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

samples/damon: fix damon sample prcl for start failure

2025-07-10T04:07:54+00:00

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