On 2024/7/14 17:05, Ryan Roberts wrote:
On 13/07/2024 13:54, Baolin Wang wrote:
On 2024/7/13 19:00, Ryan Roberts wrote:
[...]
+static int thpsize_create(int order, struct kobject *parent)
{
unsigned long size = (PAGE_SIZE << order) / SZ_1K;
+ struct thpsize_child *stats;
struct thpsize *thpsize;
int ret;
+ /*
+ * Each child object (currently only "stats" directory) holds a
+ * reference to the top-level thpsize object, so we can drop our ref to
+ * the top-level once stats is setup. Then we just need to drop a
+ * reference on any children to clean everything up. We can't just use
+ * the attr group name for the stats subdirectory because there may be
+ * multiple attribute groups to populate inside stats and overlaying
+ * using the name property isn't supported in that way; each attr group
+ * name, if provided, must be unique in the parent directory.
+ */
+
thpsize = kzalloc(sizeof(*thpsize), GFP_KERNEL);
- if (!thpsize)
- return ERR_PTR(-ENOMEM);
+ if (!thpsize) {
+ ret = -ENOMEM;
+ goto err;
+ }
+ thpsize->order = order;
ret = kobject_init_and_add(&thpsize->kobj, &thpsize_ktype, parent,
"hugepages-%lukB", size);
if (ret) {
kfree(thpsize);
- return ERR_PTR(ret);
+ goto err;
}
- ret = sysfs_create_group(&thpsize->kobj, &thpsize_attr_group);
- if (ret) {
+ stats = kzalloc(sizeof(*stats), GFP_KERNEL);
+ if (!stats) {
kobject_put(&thpsize->kobj);
- return ERR_PTR(ret);
+ ret = -ENOMEM;
+ goto err;
}
- ret = sysfs_create_group(&thpsize->kobj, &stats_attr_group);
+ ret = kobject_init_and_add(&stats->kobj, &thpsize_child_ktype,
+ &thpsize->kobj, "stats");
+ kobject_put(&thpsize->kobj);
if (ret) {
- kobject_put(&thpsize->kobj);
- return ERR_PTR(ret);
+ kfree(stats);
+ goto err;
}
- thpsize->order = order;
- return thpsize;
+ if (BIT(order) & THP_ORDERS_ALL_ANON) {
+ ret = sysfs_create_group(&thpsize->kobj, &thpsize_attr_group);
+ if (ret)
+ goto err_put;
+
+ ret = sysfs_create_group(&stats->kobj, &stats_attr_group);
+ if (ret)
+ goto err_put;
+ }
+
+ if (BIT(order) & PAGECACHE_LARGE_ORDERS) {
+ ret = sysfs_create_group(&stats->kobj, &file_stats_attr_group);
+ if (ret)
+ goto err_put;
+ }
+
+ list_add(&stats->node, &thpsize_child_list);
+ return 0;
+err_put:
IIUC, I think you should call 'sysfs_remove_group' to remove the group before
putting the kobject.
Are you sure about that? As I understood it, sysfs_create_group() was
conceptually modifying the state of the kobj, so when the kobj gets destroyed,
all its state is tidied up. __kobject_del() (called on the last kobject_put())
calls sysfs_remove_groups() and tidies up the sysfs state as far as I can see?
IIUC, __kobject_del() only removes the ktype defaut groups by
'sysfs_remove_groups(kobj, ktype->default_groups)', but your created groups are
not added into the ktype->default_groups. That means you should mannuly remove
them, or am I miss something?
That was also putting doubt in my mind. But the sample at
samples/kobject/kobject-example.c does not call sysfs_remove_group(). It just
calls sysfs_create_group() in example_init() and calls kobject_put() in
example_exit(). So I think that's the correct pattern.
Looking at the code more closely, sysfs_create_group() just creates files for
each of the attributes in the group. __kobject_del() calls sysfs_remove_dir(),
who's comment states "we remove any files in the directory before we remove the
directory" so I'm pretty sure sysfs_remove_group() is not required.
Thanks for the explanation, and I think you are right after checking the
code again. Sorry for the noise.
