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Sat, 28 Mar 2026 01:45:28 -0700 (PDT) Received: from celestia.taila51cc2.ts.net ([2402:1980:898b:301c:d085:a35:99e7:ffec]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82ca8628f39sm1464054b3a.58.2026.03.28.01.45.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 28 Mar 2026 01:45:28 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: damon@lists.linux.dev, linux-mm@kvack.org, Liew Rui Yan Subject: [PATCH] mm/damon: add synchronous commit for commit_inputs Date: Sat, 28 Mar 2026 16:45:24 +0800 Message-ID: <20260328084524.5451-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 06B4E4000C X-Stat-Signature: apqc436mfjoaap3b33q4bicny4zxcrrt X-HE-Tag: 1774687529-186843 X-HE-Meta: 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 1lEB17Si Nn5kXIGESE/ASPdF4IsgjvseTqmgFgWHSARXSrPySKOvNWe8nStjzFpq4Nq0tve7HFQ7/yPnj6NcGGZSE83UfLQlw4pCK+OeK3mBbTr7yxn0PXg9sTYMJw4VyLFIykgtK7ftwQqCFTF5GhXIAr3DxO+RsM+M1EOgzkQo6k2XEYK4OmXGxT7Pr0dVmEZffXje+DAzvjFFt4dJqqBKqef0VrLIJqDRpbjWpUKPaaU/zdN7ZVqaUPsmYW49vOKEAPWr/P4N+g/lN0syY6C/+EBNRY7ZfJj1X3DyNTTTUy8KBk90Db7l/nnNIymsPVqNhQV3s1BDh7eJDaMfqrfO4fuOj34pi+rLeDaW11LJlu9igQKDkj1W62+VPqxymIuBa3iGekkG5ZzV1KUWYrYGyDpM+E1dht0rInrZPwpN0R1repCdFfcsm1RVrGm/YNWcQBwaPDk+3oyKYq6G497ksZx5+orONDCFGMVXPgUI6FWEF64dsAJE= 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-v6: - Removed unnecessary assignment (repeat) in commit_inputs_store(). - Change the return value; if an error occurs, return the error code. - Removed the RFC tag. - Link to RFC-v6: https://lore.kernel.org/20260327062558.66392-1-aethernet65535@gmail.com Changes from RFC-v5: - Removed unnecessary assignment (data) in commit_inputs_store(). - Return -EINVAL instead of -EBUSY when 'commit_inputs' is triggered while kdamond is not running. - Link to RFC-v5: https://lore.kernel.org/20260325013939.18167-1-aethernet65535@gmail.com Changes from RFC-v4: - Rename the 'yes' variable in commit_inputs_store() to the more understandable 'commit_inputs_request'. - Return -EBUSY instead of -EINVAL when 'commit_inputs' is triggered while kdamond is not running. - Link to RFC-v4: https://lore.kernel.org/20260323021648.6590-1-aethernet65535@gmail.com 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 | 41 ++++++++++++++++++++++++++++++++++------- mm/damon/reclaim.c | 41 ++++++++++++++++++++++++++++++++++------- 2 files changed, 68 insertions(+), 14 deletions(-) diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c index 554559d72976..3af6854ba3da 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 +348,46 @@ 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 commit_inputs_request; int err; + struct damon_call_control control = { + .fn = damon_lru_sort_commit_inputs_fn, + }; + + err = kstrtobool(val, &commit_inputs_request); + if (err) + return err; - if (!commit_inputs) + if (!commit_inputs_request) return 0; - err = damon_lru_sort_apply_parameters(); - commit_inputs = false; - return err; + /* + * Skip damon_call() if ctx is not initialized to avoid + * NULL pointer dereference. + */ + if (!ctx) + return -EINVAL; + + err = damon_call(ctx, &control); + + 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 +401,7 @@ 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..d8398161f091 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 +254,46 @@ 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 commit_inputs_request; int err; + struct damon_call_control control = { + .fn = damon_reclaim_commit_inputs_fn, + }; - if (!commit_inputs) + err = kstrtobool(val, &commit_inputs_request); + if (err) + return err; + + if (!commit_inputs_request) return 0; - err = damon_reclaim_apply_parameters(); - commit_inputs = false; - return err; + /* + * Skip damon_call() if ctx is not initialized to avoid + * NULL pointer dereference. + */ + if (!ctx) + return -EINVAL; + + err = damon_call(ctx, &control); + + 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 +303,7 @@ 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