mm/damon/sysfs-schemes: implement fail_charge_{num,denom} files

Implement the user-space ABI for the DAMOS action failed region
quota-charge ratio setup.  For this, add two new sysfs files under the
DAMON sysfs interface for DAMOS quotas.  Names of the files are
fail_charge_num and fail_charge_denom, and work for reading and setting
the numerator and denominator of the failed regions charge ratio.

Link: https://lore.kernel.org/20260428013402.115171-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index d12e741a47ec8bb0b2f54cd27bc582d6a8e7cea2..be2b5eda84e0b63bcead08f179cd9d1bc31c5b69 100644 (file)
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1512,6 +1512,8 @@ struct damon_sysfs_quotas {
        unsigned long reset_interval_ms;
        unsigned long effective_sz;     /* Effective size quota in bytes */
        enum damos_quota_goal_tuner goal_tuner;
+       unsigned int fail_charge_num;
+       unsigned int fail_charge_denom;
 };
 
 static struct damon_sysfs_quotas *damon_sysfs_quotas_alloc(void)
@@ -1686,6 +1688,48 @@ static ssize_t goal_tuner_store(struct kobject *kobj,
        return -EINVAL;
 }
 
+static ssize_t fail_charge_num_show(struct kobject *kobj,
+               struct kobj_attribute *attr, char *buf)
+{
+       struct damon_sysfs_quotas *quotas = container_of(kobj,
+                       struct damon_sysfs_quotas, kobj);
+
+       return sysfs_emit(buf, "%u\n", quotas->fail_charge_num);
+}
+
+static ssize_t fail_charge_num_store(struct kobject *kobj,
+               struct kobj_attribute *attr, const char *buf, size_t count)
+{
+       struct damon_sysfs_quotas *quotas = container_of(kobj,
+                       struct damon_sysfs_quotas, kobj);
+       int err = kstrtouint(buf, 0, &quotas->fail_charge_num);
+
+       if (err)
+               return -EINVAL;
+       return count;
+}
+
+static ssize_t fail_charge_denom_show(struct kobject *kobj,
+               struct kobj_attribute *attr, char *buf)
+{
+       struct damon_sysfs_quotas *quotas = container_of(kobj,
+                       struct damon_sysfs_quotas, kobj);
+
+       return sysfs_emit(buf, "%u\n", quotas->fail_charge_denom);
+}
+
+static ssize_t fail_charge_denom_store(struct kobject *kobj,
+               struct kobj_attribute *attr, const char *buf, size_t count)
+{
+       struct damon_sysfs_quotas *quotas = container_of(kobj,
+                       struct damon_sysfs_quotas, kobj);
+       int err = kstrtouint(buf, 0, &quotas->fail_charge_denom);
+
+       if (err)
+               return -EINVAL;
+       return count;
+}
+
 static void damon_sysfs_quotas_release(struct kobject *kobj)
 {
        kfree(container_of(kobj, struct damon_sysfs_quotas, kobj));
@@ -1706,12 +1750,20 @@ static struct kobj_attribute damon_sysfs_quotas_effective_bytes_attr =
 static struct kobj_attribute damon_sysfs_quotas_goal_tuner_attr =
                __ATTR_RW_MODE(goal_tuner, 0600);
 
+static struct kobj_attribute damon_sysfs_quotas_fail_charge_num_attr =
+               __ATTR_RW_MODE(fail_charge_num, 0600);
+
+static struct kobj_attribute damon_sysfs_quotas_fail_charge_denom_attr =
+               __ATTR_RW_MODE(fail_charge_denom, 0600);
+
 static struct attribute *damon_sysfs_quotas_attrs[] = {
        &damon_sysfs_quotas_ms_attr.attr,
        &damon_sysfs_quotas_sz_attr.attr,
        &damon_sysfs_quotas_reset_interval_ms_attr.attr,
        &damon_sysfs_quotas_effective_bytes_attr.attr,
        &damon_sysfs_quotas_goal_tuner_attr.attr,
+       &damon_sysfs_quotas_fail_charge_num_attr.attr,
+       &damon_sysfs_quotas_fail_charge_denom_attr.attr,
        NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_quotas);
@@ -2803,6 +2855,8 @@ static struct damos *damon_sysfs_mk_scheme(
                .weight_nr_accesses = sysfs_weights->nr_accesses,
                .weight_age = sysfs_weights->age,
                .goal_tuner = sysfs_quotas->goal_tuner,
+               .fail_charge_num = sysfs_quotas->fail_charge_num,
+               .fail_charge_denom = sysfs_quotas->fail_charge_denom,
        };
        struct damos_watermarks wmarks = {
                .metric = sysfs_wmarks->metric,