From e6a0deb6fa5b0fc134ee2aa127d1cfc9456d8445 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Mon, 8 Sep 2025 13:15:12 -0700 Subject: mm/damon/core: introduce damon_call_control->dealloc_on_cancel 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.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'mm') diff --git a/mm/damon/core.c b/mm/damon/core.c index c2e0b469fd43..08065b363972 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2479,10 +2479,14 @@ static void kdamond_call(struct damon_ctx *ctx, bool cancel) mutex_lock(&ctx->call_controls_lock); list_del(&control->list); mutex_unlock(&ctx->call_controls_lock); - if (!control->repeat) + if (!control->repeat) { complete(&control->completion); - else + } else if (control->canceled && control->dealloc_on_cancel) { + kfree(control); + continue; + } else { list_add(&control->list, &repeat_controls); + } } control = list_first_entry_or_null(&repeat_controls, struct damon_call_control, list); -- cgit v1.2.3