kernel/linux.git/include/linux/damon.h, branch v6.18.21

mm/damon/core: avoid use of half-online-committed context

2026-04-02T11:23:29+00:00

commit 26f775a054c3cda86ad465a64141894a90a9e145 upstream. One major usage of damon_call() is online DAMON parameters update. It is done by calling damon_commit_ctx() inside the damon_call() callback function. damon_commit_ctx() can fail for two reasons: 1) invalid parameters and 2) internal memory allocation failures. In case of failures, the damon_ctx that attempted to be updated (commit destination) can be partially updated (or, corrupted from a perspective), and therefore shouldn't be used anymore. The function only ensures the damon_ctx object can safely deallocated using damon_destroy_ctx(). The API callers are, however, calling damon_commit_ctx() only after asserting the parameters are valid, to avoid damon_commit_ctx() fails due to invalid input parameters. But it can still theoretically fail if the internal memory allocation fails. In the case, DAMON may run with the partially updated damon_ctx. This can result in unexpected behaviors including even NULL pointer dereference in case of damos_commit_dests() failure [1]. Such allocation failure is arguably too small to fail, so the real world impact would be rare. But, given the bad consequence, this needs to be fixed. Avoid such partially-committed (maybe-corrupted) damon_ctx use by saving the damon_commit_ctx() failure on the damon_ctx object. For this, introduce damon_ctx->maybe_corrupted field. damon_commit_ctx() sets it when it is failed. kdamond_call() checks if the field is set after each damon_call_control->fn() is executed. If it is set, ignore remaining callback requests and return. All kdamond_call() callers including kdamond_fn() also check the maybe_corrupted field right after kdamond_call() invocations. If the field is set, break the kdamond_fn() main loop so that DAMON sill doesn't use the context that might be corrupted. [sj@kernel.org: let kdamond_call() with cancel regardless of maybe_corrupted] Link: https://lkml.kernel.org/r/20260320031553.2479-1-sj@kernel.org Link: https://sashiko.dev/#/patchset/20260319145218.86197-1-sj%40kernel.org Link: https://lkml.kernel.org/r/20260319145218.86197-1-sj@kernel.org Link: https://lore.kernel.org/20260319043309.97966-1-sj@kernel.org [1] Fixes: 3301f1861d34 ("mm/damon/sysfs: handle commit command using damon_call()") Signed-off-by: SeongJae Park Cc: [6.15+] Signed-off-by: Andrew Morton Signed-off-by: SeongJae Park Signed-off-by: Greg Kroah-Hartman

mm/damon/core: implement damon_initialized() function

2025-09-21T21:22:37+00:00

Patch series "mm/damon: define and use DAMON initialization check function". DAMON is initialized in subsystem initialization time, by damon_init(). If DAMON API functions are called before the initialization, the system could crash. Actually such issues happened and were fixed [1] in the past. For the fix, DAMON API callers have updated to check if DAMON is initialized or not, using their own hacks. The hacks are unnecessarily duplicated on every DAMON API callers and therefore it would be difficult to reliably maintain in the long term. Make it reliable and easy to maintain. For this, implement a new DAMON core layer API function that returns if DAMON is successfully initialized. If it returns true, it means DAMON API functions are safe to be used. After the introduction of the new API, update DAMON API callers to use the new function instead of their own hacks. This patch (of 7): If DAMON is tried to be used when it is not yet successfully initialized, the caller could be crashed. DAMON core layer is not providing a reliable way to see if it is successfully initialized and therefore ready to be used, though. As a result, DAMON API callers are implementing their own hacks to see it. The hacks simply assume DAMON should be ready on module init time. It is not reliable as DAMON initialization can indeed fail if KMEM_CACHE() fails, and difficult to maintain as those are duplicates. Implement a core layer API function for better reliability and maintainability to replace the hacks with followup commits. Link: https://lkml.kernel.org/r/20250916033511.116366-2-sj@kernel.org Link: https://lkml.kernel.org/r/20250916033511.116366-2-sj@kernel.org Link: https://lore.kernel.org/20250909022238.2989-1-sj@kernel.org [1] Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

Merge branch 'mm-hotfixes-stable' into mm-stable in order to pick up

2025-09-21T21:19:36+00:00

changes required by mm-stable material: hugetlb and damon.

mm/damon: add damon_ctx->min_sz_region

2025-09-13T23:55:24+00:00

Adopting addr_unit would make DAMON_MINREGION 'addr_unit * 4096' bytes and cause data alignment issues[1]. Add damon_ctx->min_sz_region to change DAMON_MIN_REGION from a global macro value to per-context variable. Link: https://lkml.kernel.org/r/20250828171242.59810-12-sj@kernel.org Link: https://lore.kernel.org/all/527714dd-0e33-43ab-bbbd-d89670ba79e7@huawei.com [1] Signed-off-by: Quanmin Yan Signed-off-by: SeongJae Park Reviewed-by: SeongJae Park Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Kefeng Wang Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: ze zuo Signed-off-by: Andrew Morton

mm/damon/core: add damon_ctx->addr_unit

2025-09-13T23:55:21+00:00

Patch series "mm/damon: support ARM32 with LPAE", v3. Previously, DAMON's physical address space monitoring only supported memory ranges below 4GB on LPAE-enabled systems. This was due to the use of 'unsigned long' in 'struct damon_addr_range', which is 32-bit on ARM32 even with LPAE enabled[1]. To add DAMON support for ARM32 with LPAE enabled, a new core layer parameter called 'addr_unit' was introduced[2]. Operations set layer can translate a core layer address to the real address by multiplying the parameter value to the core layer address. Support of the parameter is up to each operations layer implementation, though. For example, operations set implementations for virtual address space can simply ignore the parameter. Add the support on paddr, which is the DAMON operations set implementation for the physical address space, as we have a clear use case for that. This patch (of 11): In some cases, some of the real address that handled by the underlying operations set cannot be handled by DAMON since it uses only 'unsinged long' as the address type. Using DAMON for physical address space monitoring of 32 bit ARM devices with large physical address extension (LPAE) is one example[1]. Add a parameter name 'addr_unit' to core layer to help such cases. DAMON core API callers can set it as the scale factor that will be used by the operations set for translating the core layer's addresses to the real address by multiplying the parameter value to the core layer address. Support of the parameter is up to each operations set layer. The support from the physical address space operations set (paddr) will be added with following commits. Link: https://lkml.kernel.org/r/20250828171242.59810-1-sj@kernel.org Link: https://lkml.kernel.org/r/20250828171242.59810-2-sj@kernel.org Link: https://lore.kernel.org/20250408075553.959388-1-zuoze1@huawei.com [1] Link: https://lore.kernel.org/all/20250416042551.158131-1-sj@kernel.org/ [2] Signed-off-by: SeongJae Park Signed-off-by: Quanmin Yan Reviewed-by: SeongJae Park Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Kefeng Wang Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: ze zuo Signed-off-by: Andrew Morton

mm/damon: update expired description of damos_action

2025-09-13T23:54:49+00:00

Nowadays, damos operation actions support a greater operation set. But comments (also, generated documentation) weren't updated. So fix the comments with current support status. Link: https://lkml.kernel.org/r/20250805123940.13691-1-ekffu200098@gmail.com Signed-off-by: Sang-Heon Jeon Reviewed-by: SeongJae Park Cc: Honggyu Kim Signed-off-by: Andrew Morton

mm/damon/core: introduce damon_call_control->dealloc_on_cancel

2025-09-13T20:05:36+00:00

Patch series "mm/damon/sysfs: fix refresh_ms control overwriting on multi-kdamonds usages". Automatic esssential DAMON/DAMOS status update feature of DAMON sysfs interface (refresh_ms) is broken [1] for multiple DAMON contexts (kdamonds) use case, since it uses a global single damon_call_control object for all created DAMON contexts. The fields of the object, particularly the list field is over-written for the contexts and it makes unexpected results including user-space hangup and kernel crashes [2]. Fix it by extending damon_call_control for the use case and updating the usage on DAMON sysfs interface to use per-context dynamically allocated damon_call_control object. This patch (of 2): When damon_call_control->repeat is set, damon_call() is executed asynchronously, and is eventually canceled when kdamond finishes. If the damon_call_control object is dynamically allocated, finding the place to deallocate the object is difficult. Introduce a new damon_call_control field, namely dealloc_on_cancel, to ask the kdamond deallocates those dynamically allocated objects when those are canceled. Link: https://lkml.kernel.org/r/20250908201513.60802-3-sj@kernel.org Link: https://lkml.kernel.org/r/20250908201513.60802-2-sj@kernel.org Fixes: d809a7c64ba8 ("mm/damon/sysfs: implement refresh_ms file internal work") Signed-off-by: SeongJae Park Cc: Yunjeong Mun Signed-off-by: Andrew Morton

mm/damon/core: remove damon_callback

2025-07-20T01:59:57+00:00

All damon_callback usages are replicated by damon_call() and damos_walk(). Time to say goodbye. Remove damon_callback. Link: https://lkml.kernel.org/r/20250712195016.151108-15-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

mm/damon/core: add cleanup_target() ops callback

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

Some DAMON operation sets may need additional cleanup per target. For example, [f]vaddr need to put pids of each target. Each user and core logic is doing that redundantly. Add another DAMON ops callback that will be used for doing such cleanups in operations set layer. [sj@kernel.org: add kernel-doc comment for damon_operations->cleanup_target] Link: https://lkml.kernel.org/r/20250715185239.89152-2-sj@kernel.org [sj@kernel.org: remove damon_ctx->callback kernel-doc comment] Link: https://lkml.kernel.org/r/20250715185239.89152-3-sj@kernel.org Link: https://lkml.kernel.org/r/20250712195016.151108-10-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton

mm/damon/core: introduce repeat mode damon_call()

2025-07-20T01:59:54+00:00

damon_call() can be useful for reading or writing DAMON internal data for one time. A common pattern of DAMON core usage from DAMON modules is doing such reads and writes repeatedly, for example, to periodically update the DAMOS stats. To do that with damon_call(), callers should call damon_call() repeatedly, with their own delay loop. Each caller doing that is repetitive. Introduce a repeat mode damon_call(). Callers can use the mode by setting a new field in damon_call_control. If the mode is turned on, damon_call() returns success immediately, and DAMON repeats invoking the callback function inside the kdamond main loop. Link: https://lkml.kernel.org/r/20250712195016.151108-3-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton