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Tue, 24 Mar 2026 18:39:45 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: damon@lists.linux.dev, linux-mm@kvack.org, Liew Rui Yan Subject: [RFC v5] mm/damon: add synchronous commit for commit_inputs Date: Wed, 25 Mar 2026 09:39:39 +0800 Message-ID: <20260325013939.18167-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 4C65BA0008 X-Stat-Signature: rwbybpa4oymjhb58oezqc9h5b3thpoo9 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1774402787-906599 X-HE-Meta: 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 a/uexaH1 lLdeNX70HuVv1QTZbNb30y2f6gGidrwPV6C2Eki3KmYkgJ26AACkkB++eWebvHaeXk5Fu6X8S37+dz9bYspm1JKMmIq4xVtk34tnBW0zySITYioBhUukGvqc6REQuOc/AwlEs62A+fUWf4iZRklkWbVh4k28Msf439UYhoXVEo3CVhLdM1otjzPJuCZXdy/9X0DCCqZEKpRcIBHqJKSFNqO1Ze+jAOV+eWjOddRUZoTwjalfq43smR3iIpn8218C7VvVp1pGhp1aLV+gvHWcM1fqS9U5fgLISpSl4iSqHOic+aqy7Y0TVT7+ZHElzaRjB1C1kbJZl4kJI6stW93WOAYHgVdsnPRK5QkvUfu/tnXwgruxSUOqCxIr9ALlhEh3swuT3+ZajpUb9MFF6J9f63/arQ5m3rXAj4a1rNDKhPCXMTALar1RVWfCcVpvtV74h5l65U6Gq+PI1+cWx6DjUgjuYJDflOKMWNb5y9EmEhMQapT8= 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-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 | 54 +++++++++++++++++++++++++++++++++++++++------ mm/damon/reclaim.c | 54 +++++++++++++++++++++++++++++++++++++++------ 2 files changed, 94 insertions(+), 14 deletions(-) diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c index 554559d72976..a2410f648b51 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 +348,59 @@ 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, + .data = ctx, + .repeat = false, + }; - if (!commit_inputs) + err = kstrtobool(val, &commit_inputs_request); + if (err) + return err; + + if (!commit_inputs_request) return 0; - err = damon_lru_sort_apply_parameters(); - commit_inputs = false; - return err; + /* + * Skip damon_call() during early boot or when kdamond is + * not running to avoid NULL pointer dereference. + */ + if (!ctx) + return -EBUSY; + + err = damon_call(ctx, &control); + if (err) { + /* + * If kdamond is not running, damon_call() returns -EINVAL. + * Remap it to -EBUSY to better reflect that the operation + * failed due to the current state of the system. + */ + if (err == -EINVAL && !damon_is_running(ctx)) + return -EBUSY; + + return err; + } + + return 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 +414,7 @@ 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..4cbd67e08d56 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 +254,59 @@ 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, + .data = ctx, + .repeat = false, + }; - 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() during early boot or when kdamond is + * not running to avoid NULL pointer dereference. + */ + if (!ctx) + return -EBUSY; + + err = damon_call(ctx, &control); + if (err) { + /* + * If kdamond is not running, damon_call() returns -EINVAL. + * Remap it to -EBUSY to better reflect that the operation + * failed due to the current state of the system. + */ + if (err == -EINVAL && !damon_is_running(ctx)) + return -EBUSY; + + return err; + } + + return 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 +316,7 @@ 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