The patch titled Subject: mm/damon/core: handle damon_call_control as normal under kdmond deactivation has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-core-handle-damon_call_control-as-normal-under-kdmond-deactivation.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: SeongJae Park sj@kernel.org Subject: mm/damon/core: handle damon_call_control as normal under kdmond deactivation Date: Sun, 29 Jun 2025 13:49:14 -0700
DAMON sysfs interface internally uses damon_call() to update DAMON parameters as users requested, online. However, DAMON core cancels any damon_call() requests when it is deactivated by DAMOS watermarks.
As a result, users cannot change DAMON parameters online while DAMON is deactivated. Note that users can turn DAMON off and on with different watermarks to work around. Since deactivated DAMON is nearly same to stopped DAMON, the work around should have no big problem. Anyway, a bug is a bug.
There is no real good reason to cancel the damon_call() request under DAMOS deactivation. Fix it by simply handling the request as normal, rather than cancelling under the situation.
Link: https://lkml.kernel.org/r/20250629204914.54114-1-sj@kernel.org Fixes: 42b7491af14c ("mm/damon/core: introduce damon_call()") Signed-off-by: SeongJae Park sj@kernel.org Cc: stable@vger.kernel.org [6.14+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/damon/core.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
--- a/mm/damon/core.c~mm-damon-core-handle-damon_call_control-as-normal-under-kdmond-deactivation +++ a/mm/damon/core.c @@ -2355,9 +2355,8 @@ static void kdamond_usleep(unsigned long * * If there is a &struct damon_call_control request that registered via * &damon_call() on @ctx, do or cancel the invocation of the function depending - * on @cancel. @cancel is set when the kdamond is deactivated by DAMOS - * watermarks, or the kdamond is already out of the main loop and therefore - * will be terminated. + * on @cancel. @cancel is set when the kdamond is already out of the main loop + * and therefore will be terminated. */ static void kdamond_call(struct damon_ctx *ctx, bool cancel) { @@ -2405,7 +2404,7 @@ static int kdamond_wait_activation(struc if (ctx->callback.after_wmarks_check && ctx->callback.after_wmarks_check(ctx)) break; - kdamond_call(ctx, true); + kdamond_call(ctx, false); damos_walk_cancel(ctx); } return -EBUSY; _
Patches currently in -mm which might be from sj@kernel.org are
mm-damon-core-handle-damon_call_control-as-normal-under-kdmond-deactivation.patch mm-damon-introduce-damon_stat-module.patch mm-damon-introduce-damon_stat-module-fix.patch mm-damon-stat-calculate-and-expose-estimated-memory-bandwidth.patch mm-damon-stat-calculate-and-expose-idle-time-percentiles.patch docs-admin-guide-mm-damon-add-damon_stat-usage-document.patch mm-damon-paddr-use-alloc_migartion_target-with-no-migration-fallback-nodemask.patch revert-mm-rename-alloc_demote_folio-to-alloc_migrate_folio.patch revert-mm-make-alloc_demote_folio-externally-invokable-for-migration.patch selftets-damon-add-a-test-for-memcg_path-leak.patch mm-damon-sysfs-schemes-decouple-from-damos_quota_goal_metric.patch mm-damon-sysfs-schemes-decouple-from-damos_action.patch mm-damon-sysfs-schemes-decouple-from-damos_wmark_metric.patch mm-damon-sysfs-schemes-decouple-from-damos_filter_type.patch mm-damon-sysfs-decouple-from-damon_ops_id.patch