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Fri, 20 Mar 2026 17:26:48 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: damon@lists.linux.dev, linux-mm@kvack.org, Liew Rui Yan Subject: [RFC PATCH] mm/damon/lru_sort: add synchronous validation for commit_inputs Date: Sat, 21 Mar 2026 08:26:42 +0800 Message-ID: <20260321002642.22712-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 15c3hge5jsqtu9ctyu3u9xtiingfojii X-Rspam-User: X-Rspamd-Queue-Id: 8FDBC18000D X-Rspamd-Server: rspam12 X-HE-Tag: 1774052810-207736 X-HE-Meta: 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 Fno5fpq6 nSfjRDh/tgP6ITHvPmFJyPWIp/1EnJIPkimP86suXnOpjRoHT8rmOBwqBE56W/vYp//QyO2TLXudxgtQhbb2S7xeTKFrHLUn4prsTvN4WD/r+ANRnthTSqtbEkNeRNVCx1VX5zcI+ICbhRyjN9/0vZ3d//e83E0yLO7HF5eIbgjhJ1bzoG0OGej+p65DGsB3acgxPzfGR6Sq48ZFjdpLq2Q2FxANe7r87rHByYGKt8HL4gPpw+FCnEgi9WbG1qZpVS6SePR1ta3LTOf+F+K4MhXiyqhzeT0nlE8Es2p1vITm7QMthCaaNK0ALZ/zZo1V8cc76iDhY88ttMmbBdWPWfMqRQPjpK56VCjtiUJOkdff3RVTA7eS7CbCC6zUCF5ZWxU/CkXOmGSx7w8af1jEaj1mx1JLtRFAkZb1aKT1WQcen1y2wnd4ev5Sn+qLBoMVyKS78aKHPJlbQ8/1D1IkvqLhHYeqrSD6sqTdGfuZt2ZD5A2w= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi SeongJae, I would like to ask some question about the fourth task in discussion [1]. Please let me state first that the following changes will also apply to the DAMON_RECLAIM module. Problem ======= Writing invalid parameters to sysfs followed by 'commit_inputs=Y' fails silently (no error returned to shell), because the validation happens aynchronously in the kdamond. Solution ======== To fix this, I proposed adding synchronous validation in damon_lru_sort_commit_inputs_store() before setting the 'commit_inputs' flag. This allow users to receive immediate feedback (e.g., -EINVAL) if the parameters are invalid. Changes ======= 1. Added damon_lru_sort_commit_inputs_store() to handle parameter validation before setting 'commit_inputs'. 2. Added damon_valid_attrs() to centralize validation logic. 3. Extracted validation checks from damon_lru_sort_apply_parameters() (currently copied from core.c). Questions ========= - Design: Is this synchronous validation approach acceptable? Or do you prefer keeping it purely asynchronous? - Code Structure: I noticed damon_valid_intervals_goal() and similar validation logic exist in core.c but are static. To avoid duplication, should I: a) Export a generic validation function in damon.h or internal.h? b) Keep the copy in lru_sort.c? - Concurrency: Are there any race conditions I should be aware of when reading 'damon_lru_sort_mon_attrs' in the store function? Should I use READ_ONCE() or add explicit locking? Thanks for your time reviewing this! :> Best regards, Rui Yan [1] https://lore.kernel.org/20260319151528.86490-1-sj@kernel.org Signed-off-by: Liew Rui Yan --- mm/damon/lru_sort.c | 64 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 63 insertions(+), 1 deletion(-) diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c index 554559d72976..0e5f9d29e294 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). @@ -361,6 +360,69 @@ static int damon_lru_sort_handle_commit_inputs(void) return err; } +/* Source: mm/damon/core.c */ +static bool damon_valid_intervals_goal(struct damon_attrs *attrs) +{ + struct damon_intervals_goal *goal = &attrs->intervals_goal; + + /* tuning is disabled */ + if (!goal->aggrs) + return true; + if (goal->min_sample_us > goal->max_sample_us) + return false; + if (attrs->sample_interval < goal->min_sample_us || + goal->max_sample_us < attrs->sample_interval) + return false; + return true; +} + +static int damon_valid_attrs(struct damon_attrs *attrs) +{ + if (!damon_valid_intervals_goal(attrs)) + return -EINVAL; + if (attrs->min_nr_regions < 3) + return -EINVAL; + if (attrs->min_nr_regions > attrs->max_nr_regions) + return -EINVAL; + if (attrs->sample_interval > attrs->aggr_interval) + return -EINVAL; + + return 0; +} + +static int damon_lru_sort_commit_inputs_store(const char *val, + const struct kernel_param *kp) +{ + struct damon_attrs attrs; + bool yes; + int err; + + err = kstrtobool(val, &yes); + if (err) + return err; + + if (commit_inputs == yes) + return 0; + + if (!yes) + return 0; + + attrs = damon_lru_sort_mon_attrs; + err = damon_valid_attrs(&attrs); + if (err) + return err; + + commit_inputs = yes; + return err; +} + +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; -- 2.53.0