When pinning cgroup_view iter into bpffs, the pinning adds a tag to
the parent directory, indicating the underneath directory hierarchy
is a replicate of the cgroup hierarchy. Each of the directory connects
to a cgroup directory. Whenever a subdirectory is created, if there is
a subcgroup of the same name exists, the subdirectory will be populated
with entries holding a list of bpf objects registered in the tag's
inherit list. The inherit list is formed by the objects pinned in the
top level tagged directory. For example,
bpf_obj_pin(cgroup_view_link, "/sys/fs/bpf/A/obj");
pins a link in A. A becomes tagged and the link object is registered
in the inherit list of A's tag.
mkdir("/sys/fs/bpf/A/B");
When A/B is created, B inherits the pinned objects in A. B is populated
with objects.
> ls /sys/fs/bpf/A/B
obj
Currently, only pinning cgroup_view link can tag a directory. And once
tagged, only rmdir can remove the tag.
Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx>
---
kernel/bpf/inode.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 84 insertions(+)
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 9ae17a2bf779..b71840bf979d 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -71,6 +71,7 @@ static void free_obj_list(struct kref *kref)
list_for_each_entry(e, &list->list, list) {
list_del_rcu(&e->list);
bpf_any_put(e->obj, e->type);
+ kfree(e->name.name);
kfree(e);
}
kfree(list);
@@ -486,9 +487,20 @@ static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
&bpffs_map_fops : &bpffs_obj_fops);
}
+static int
+bpf_inherit_object(struct dentry *dentry, umode_t mode, void *obj,
+ enum bpf_type type);
+
static int bpf_mklink(struct dentry *dentry, umode_t mode, void *arg)
{
struct bpf_link *link = arg;
+ int err;
+
+ if (bpf_link_support_inherit(link)) {
+ err = bpf_inherit_object(dentry, mode, link, BPF_TYPE_LINK);
+ if (err)
+ return err;
+ }
return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops,
bpf_link_is_iter(link) ?
@@ -586,6 +598,78 @@ static const struct inode_operations bpf_dir_iops = {
.unlink = simple_unlink,
};
+/* bpf_inherit_object - register an object in a diretory tag's inherit list
+ * @dentry: dentry of the location to pin
+ * @mode: mode of created file entry
+ * @obj: bpf object
+ * @type: type of bpf object
+ *
+ * Could be called from bpf_obj_do_pin() or from mkdir().
+ */
+static int bpf_inherit_object(struct dentry *dentry, umode_t mode,
+ void *obj, enum bpf_type type)
+{
+ struct inode *dir = d_inode(dentry->d_parent);
+ struct obj_list *inherits;
+ struct bpf_inherit_entry *e;
+ struct bpf_dir_tag *tag;
+ const char *name;
+ bool queued = false, new_tag = false;
+
+ /* allocate bpf_dir_tag */
+ tag = inode_tag(dir);
+ if (!tag) {
+ new_tag = true;
+ tag = kzalloc(sizeof(struct bpf_dir_tag), GFP_KERNEL);
+ if (unlikely(!tag))
+ return -ENOMEM;
+
+ tag->type = BPF_DIR_KERNFS_REP;
+ inherits = kzalloc(sizeof(struct obj_list), GFP_KERNEL);
+ if (unlikely(!inherits)) {
+ kfree(tag);
+ return -ENOMEM;
+ }
+
+ kref_init(&inherits->refcnt);
+ INIT_LIST_HEAD(&inherits->list);
+ tag->inherit_objects = inherits;
+ /* initial tag points to the default root cgroup. */
+ tag->private = cgrp_dfl_root.kf_root->kn;
+ dir->i_private = tag;
+ } else {
+ inherits = tag->inherit_objects;
+ }
+
+ list_for_each_entry_rcu(e, &inherits->list, list) {
+ if (!strcmp(dentry->d_name.name, e->name.name)) {
+ queued = true;
+ break;
+ }
+ }
+
+ /* queue in tag's inherit_list. */
+ if (!queued) {
+ e = kzalloc(sizeof(struct bpf_inherit_entry), GFP_KERNEL);
+ if (!e) {
+ if (new_tag) {
+ kfree(tag);
+ kfree(inherits);
+ }
+ return -ENOMEM;
+ }
+
+ INIT_LIST_HEAD(&e->list);
+ e->mode = mode;
+ e->obj = obj;
+ e->type = type;
+ name = kstrdup(dentry->d_name.name, GFP_USER | __GFP_NOWARN);
+ e->name = (struct qstr)QSTR_INIT(name, strlen(name));
+ list_add_rcu(&e->list, &inherits->list);
+ }
+ return 0;
+}
+
/* pin iterator link into bpffs */
static int bpf_iter_link_pin_kernel(struct dentry *parent,
const char *name, struct bpf_link *link)
--
2.35.0.rc2.247.g8bbb082509-goog
