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Sun, 29 Mar 2026 00:54:18 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: damon@lists.linux.dev, linux-mm@kvack.org, Liew Rui Yan Subject: [PATCH v2] mm/damon: add synchronous commit for commit_inputs Date: Sun, 29 Mar 2026 15:54:15 +0800 Message-ID: <20260329075415.36775-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 982D54000B X-Stat-Signature: ubuw3kwtqd5zqe6bcey8x5pt78mj75sh X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1774770860-770043 X-HE-Meta: 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 PCwWBJ8C 40wV9pgYzZtue1qaC/WVTb3THTQ7jc4o26Fsqf6c+3K7KITZO20Wb/tzInEz43iPP1MkdAOZQXc84wf/FAbMQSVPVMCqPPaOQHsSzXxCyWYRbbqtHCwy6UB8mpnrFmMbazhFsSNaWECplxR6EYHb3bBkTGu4MUMxi08Cy3FGizCdySgqlXSqmcSYjBL/qLKVGJLuojeDJH3mKa0cY4Ff75YTzvLvqfV1RjxSZMYcA7o/SXPgRXv7pNfz7eFDa6dCOyvXDS0GISCrL1Zt19msBHfboXpePwmL5+iP0dxlxRUKqx2PEyWCOXpJ+WiZ0On4GvFahliBK+tn8VdAiFrGBjADvYRvJkDDkYMYZrprsP0rl2PtSw9U5j8kqvizeWt1muBxT+fJmrZnJiWIKwz7Y53sc5T5FNujoX6nwUHU56vLaULJOUPHd4C0EeeuO03hlcqxgtpx/Opq8yf/czZkCFooVyO41QOUpwwqvR6OVIWg1s/g= 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 v1: - Restore the KERNEL_PARAM_OPS_FL_NOARG flag to keep the compatibility. - Link to V1: https://lore.kernel.org/20260328084524.5451-1-aethernet65535@gmail.com 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 | 46 ++++++++++++++++++++++++++++++++++++++------- mm/damon/reclaim.c | 46 ++++++++++++++++++++++++++++++++++++++------- 2 files changed, 78 insertions(+), 14 deletions(-) diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c index 554559d72976..641af42cc2d1 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 +348,51 @@ 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, + }; + + if (!val) { + commit_inputs_request = true; + } else { + 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 = { + .flags = KERNEL_PARAM_OPS_FL_NOARG, + .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 +406,7 @@ 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..31cf3c45dc72 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 +254,51 @@ 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) + if (!val) { + commit_inputs_request = true; + } else { + 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 = { + .flags = KERNEL_PARAM_OPS_FL_NOARG, + .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 +308,7 @@ 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