mm/damon/sysfs: add filters/<F>/path file

Introduce a new DAMON sysfs file for letting users setup the target memory
cgroup of the belonging memory cgroup attribute monitoring.  The file is
named 'path', located under the probe filter directory.  Users can set the
target memory cgroup by writing the path to the memory cgroup from the
cgroup mount point to the file.

Link: https://lore.kernel.org/20260518234119.97569-25-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
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: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.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.c b/mm/damon/sysfs.c
index eeb7fdd030cf0c5e5421a1f260d76fd1027514ac..0f6379caf4816d5cf9b2124b1f5352a43f7a9588 100644 (file)
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -756,6 +756,7 @@ struct damon_sysfs_filter {
        enum damon_filter_type type;
        bool matching;
        bool allow;
+       char *path;
 };
 
 static struct damon_sysfs_filter *damon_sysfs_filter_alloc(void)
@@ -774,6 +775,10 @@ damon_sysfs_filter_type_names[] = {
                .type = DAMON_FILTER_TYPE_ANON,
                .name = "anon",
        },
+       {
+               .type = DAMON_FILTER_TYPE_MEMCG,
+               .name = "memcg",
+       },
 };
 
 static ssize_t type_show(struct kobject *kobj,
@@ -862,11 +867,46 @@ static ssize_t allow_store(struct kobject *kobj,
        return count;
 }
 
+static ssize_t path_show(struct kobject *kobj,
+               struct kobj_attribute *attr, char *buf)
+{
+       struct damon_sysfs_filter *filter = container_of(kobj,
+                       struct damon_sysfs_filter, kobj);
+       int len;
+
+       if (!mutex_trylock(&damon_sysfs_lock))
+               return -EBUSY;
+       len = sysfs_emit(buf, "%s\n", filter->path ? filter->path : "");
+       mutex_unlock(&damon_sysfs_lock);
+       return len;
+}
+
+static ssize_t path_store(struct kobject *kobj,
+               struct kobj_attribute *attr, const char *buf, size_t count)
+{
+       struct damon_sysfs_filter *filter = container_of(kobj,
+                       struct damon_sysfs_filter, kobj);
+       char *path = kmalloc_objs(*path, size_add(count, 1));
+
+       if (!path)
+               return -ENOMEM;
+       strscpy(path, buf, size_add(count, 1));
+       if (!mutex_trylock(&damon_sysfs_lock)) {
+               kfree(path);
+               return -EBUSY;
+       }
+       kfree(filter->path);
+       filter->path = path;
+       mutex_unlock(&damon_sysfs_lock);
+       return count;
+}
+
 static void damon_sysfs_filter_release(struct kobject *kobj)
 {
        struct damon_sysfs_filter *filter = container_of(kobj,
                        struct damon_sysfs_filter, kobj);
 
+       kfree(filter->path);
        kfree(filter);
 }
 
@@ -879,10 +919,14 @@ static struct kobj_attribute damon_sysfs_filter_matching_attr =
 static struct kobj_attribute damon_sysfs_filter_allow_attr =
                __ATTR_RW_MODE(allow, 0600);
 
+static struct kobj_attribute damon_sysfs_filter_path_attr =
+               __ATTR_RW_MODE(path, 0600);
+
 static struct attribute *damon_sysfs_filter_attrs[] = {
        &damon_sysfs_filter_type_attr.attr,
        &damon_sysfs_filter_matching_attr.attr,
        &damon_sysfs_filter_allow_attr.attr,
+       &damon_sysfs_filter_path_attr.attr,
        NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_filter);