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Sun, 22 Mar 2026 19:16:53 -0700 (PDT) Received: from celestia.taila51cc2.ts.net ([2402:1980:898b:301c:d085:a35:99e7:ffec]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b083655474sm114373405ad.48.2026.03.22.19.16.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Mar 2026 19:16:52 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: damon@lists.linux.dev, linux-mm@kvack.org, Liew Rui Yan Subject: [RFC v4] mm/damon: add synchronous commit for commit_inputs Date: Mon, 23 Mar 2026 10:16:48 +0800 Message-ID: <20260323021648.6590-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 75C3720004 X-Stat-Signature: 19uxja3ked5s7thwusqmgbnsrxd675gc X-Rspam-User: X-HE-Tag: 1774232214-878184 X-HE-Meta: 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 +qMmbPqI AVmyOm/hBaN47UOrHrpPOCJrfzkoNkby1hxgLnQNxC+SpJ5q0X+CmA7aGljUD/o5/lrc2+Ysdqa55a/8S8MpnfnOaChKd0ZoGbI8LIdyA2EA1oyGEQip/qD+fgtZm7F6DPhSk1xpV77hC8ebzfna0mHK3Ui6THb9DbA54VH9A3L5GfnNO6WMGvy8jFKjMamE/DFKXS1JIEg+IdSU0v9/Cp7Jro+ro2BWK8q2HmtDbTMASkLqTCFmoQdmVsjfW3aH4zdWNFMQpdnxs7TtjKmUyZ1RJJU55AcJsK7t1jfVpB/V1awF4g/dYmyJMZ/OrVRUzB4nR9wMEFEeZbfMXg6MLllPnc13C8fyxXh1OkiNU+kAYFdVyciaFAk/OiOh4xjkNpPOYMhSkVubFD2BkYeiOGRxkFc13fCnyv0V3A5qldqtL+oNxX00CS3VbwBoK8tPQismtAKFdFON2IiS+6kWuwRN4cqz4qBf178ciFQNaebCkewc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Problem ======= Writing invalid parameters to sysfs followed by 'commit_inputs=Y' fails silently (no error returned to shell), because the validation happens asynchronously in the kdamond. Solution ======== To fix this, the commit_inputs_store() callback now uses damon_call() to synchronously commit parameters in the kdamond thread's safe context. This ensures that validation errors are returned immediately to userspace, following the pattern used by DAMON_SYSFS. Changes ======= 1. Added commit_inputs_store() and commit_inputs_fn() to commit synchronously. 2. Removed handle_commit_inputs(). This change is motivated from another discussion [1]. [1] https://lore.kernel.org/20260318153731.97470-1-aethernet65535@gmail.com Signed-off-by: Liew Rui Yan --- Changes from RFC-v3: - Added checks for 'ctx' and 'damon_is_running()' to prevent NULL pointer dereference during early boot. (Found by Sashiko.dev) - Removed handle_commit_inputs() and its associated polling logic as they have become dead code after moving to the synchronous damon_call() approach. - Ensure the 'commit_inputs' is properly updated. Link to RFC-v3: https://lore.kernel.org/20260322231522.32700-1-aethernet65535@gmail.com Changes from RFC-v2: - Removed damon_validate_attrs(), now using damon_commit_ctx() for synchronous validation in the kdamond context. - Following DAMON_SYSFS pattern for synchronous commit via damon_call(). - Link to RFC-v2: https://lore.kernel.org/20260321140926.22163-1-aethernet65535@gmail.com Changes from RFC-v1: - Remove question from commit message area. - Added synchronous validation for DAMON_RECLAIM. - Rename damon_valid_attrs() -> damon_validate_attrs(). - Exported a new function damon_validate_attrs() and declared it in damon.h. - Link to RFC-v1: https://lore.kernel.org/20260321002642.22712-1-aethernet65535@gmail.com mm/damon/lru_sort.c | 49 +++++++++++++++++++++++++++++++++++++++------ mm/damon/reclaim.c | 49 +++++++++++++++++++++++++++++++++++++++------ 2 files changed, 86 insertions(+), 12 deletions(-) diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c index 554559d72976..37b3c897e822 100644 --- a/mm/damon/lru_sort.c +++ b/mm/damon/lru_sort.c @@ -39,7 +39,6 @@ static bool enabled __read_mostly; * the re-reading, DAMON_LRU_SORT will be disabled. */ static bool commit_inputs __read_mostly; -module_param(commit_inputs, bool, 0600); /* * Desired active to [in]active memory ratio in bp (1/10,000). @@ -349,18 +348,56 @@ static int damon_lru_sort_apply_parameters(void) return err; } -static int damon_lru_sort_handle_commit_inputs(void) +static int damon_lru_sort_commit_inputs_fn(void *arg) { + return damon_lru_sort_apply_parameters(); +} + +static int damon_lru_sort_commit_inputs_store(const char *val, + const struct kernel_param *kp) +{ + bool yes; int err; + struct damon_call_control control = { + .fn = damon_lru_sort_commit_inputs_fn, + .data = ctx, + .repeat = false, + }; - if (!commit_inputs) + err = kstrtobool(val, &yes); + if (err) + return err; + + if (commit_inputs == yes) return 0; - err = damon_lru_sort_apply_parameters(); + if (!yes) { + commit_inputs = false; + return 0; + } + + commit_inputs = yes; + + /* + * Skip damon_call() during early boot or when kdamond is idle + * to avoid NULL pointer dereference or unexpected -EINVAL. + */ + if (!ctx || !damon_is_running(ctx)) + return 0; + + err = damon_call(ctx, &control); commit_inputs = false; - return err; + + return err ? err : control.return_code; } +static const struct kernel_param_ops commit_inputs_param_ops = { + .set = damon_lru_sort_commit_inputs_store, + .get = param_get_bool, +}; + +module_param_cb(commit_inputs, &commit_inputs_param_ops, &commit_inputs, 0600); + static int damon_lru_sort_damon_call_fn(void *arg) { struct damon_ctx *c = arg; @@ -374,7 +411,7 @@ static int damon_lru_sort_damon_call_fn(void *arg) damon_lru_sort_cold_stat = s->stat; } - return damon_lru_sort_handle_commit_inputs(); + return 0; } static struct damon_call_control call_control = { diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c index 86da14778658..441d5d9f9eab 100644 --- a/mm/damon/reclaim.c +++ b/mm/damon/reclaim.c @@ -39,7 +39,6 @@ static bool enabled __read_mostly; * re-reading, DAMON_RECLAIM will be disabled. */ static bool commit_inputs __read_mostly; -module_param(commit_inputs, bool, 0600); /* * Time threshold for cold memory regions identification in microseconds. @@ -255,18 +254,56 @@ static int damon_reclaim_apply_parameters(void) return err; } -static int damon_reclaim_handle_commit_inputs(void) +static int damon_reclaim_commit_inputs_fn(void *arg) { + return damon_reclaim_apply_parameters(); +} + +static int damon_reclaim_commit_inputs_store(const char *val, + const struct kernel_param *kp) +{ + bool yes; int err; + struct damon_call_control control = { + .fn = damon_reclaim_commit_inputs_fn, + .data = ctx, + .repeat = false, + }; - if (!commit_inputs) + err = kstrtobool(val, &yes); + if (err) + return err; + + if (commit_inputs == yes) return 0; - err = damon_reclaim_apply_parameters(); + if (!yes) { + commit_inputs = false; + return 0; + } + + commit_inputs = yes; + + /* + * Skip damon_call() during early boot or when kdamond is idle + * to avoid NULL pointer dereference or unexpected -EINVAL. + */ + if (!ctx || !damon_is_running(ctx)) + return 0; + + err = damon_call(ctx, &control); commit_inputs = false; - return err; + + return err ? err : control.return_code; } +static const struct kernel_param_ops commit_inputs_param_ops = { + .set = damon_reclaim_commit_inputs_store, + .get = param_get_bool, +}; + +module_param_cb(commit_inputs, &commit_inputs_param_ops, &commit_inputs, 0600); + static int damon_reclaim_damon_call_fn(void *arg) { struct damon_ctx *c = arg; @@ -276,7 +313,7 @@ static int damon_reclaim_damon_call_fn(void *arg) damon_for_each_scheme(s, c) damon_reclaim_stat = s->stat; - return damon_reclaim_handle_commit_inputs(); + return 0; } static struct damon_call_control call_control = { -- 2.53.0