On 4/23/24 10:16 AM, Kui-Feng Lee wrote:
On 4/22/24 16:43, Martin KaFai Lau wrote:
On 4/22/24 10:30 AM, Kui-Feng Lee wrote:
On 4/22/24 10:12, Kui-Feng Lee wrote:
On 4/19/24 17:05, Martin KaFai Lau wrote:
On 4/16/24 5:25 PM, Kui-Feng Lee wrote:
+int bpffs_struct_ops_link_open(struct inode *inode, struct file *filp)
+{
+ struct bpf_struct_ops_link *link = inode->i_private;
+
+ /* Paired with bpf_link_put_direct() in bpf_link_release(). */
+ bpf_link_inc(&link->link);
+ filp->private_data = link;
+ return 0;
+}
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index af5d2ffadd70..b020d761ab0a 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -360,11 +360,16 @@ static int bpf_mkmap(struct dentry *dentry, umode_t
mode, void *arg)
static int bpf_mklink(struct dentry *dentry, umode_t mode, void *arg)
{
+ const struct file_operations *fops;
struct bpf_link *link = arg;
- return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops,
- bpf_link_is_iter(link) ?
- &bpf_iter_fops : &bpffs_obj_fops);
+ if (bpf_link_is_iter(link))
+ fops = &bpf_iter_fops;
+ else if (link->type == BPF_LINK_TYPE_STRUCT_OPS)
Open a pinned link and then update should not be specific to struct_ops
link. e.g. should be useful to the cgroup link also?
It could be. Here, I played safe in case it creates any unwanted side
effect for links of unknown types.
By the way, may I put it in a follow up patch if we want cgroup links?
This does not feel right. It is not struct_ops specific.
Before we dive in further, there is BPF_OBJ_GET which can get a fd of a pinned
bpf obj (prog, map, and link). Take a look at bpf_link__open() in libbpf. Does
it work for the use case that needs to update the link?
It should work.
So, this patch is not necessary. However, it is still a nice and
intuitive feature. WDYT?
There is already BPF_OBJ_GET which works for all major bpf obj types (prog, map,
and link). Having open only works for link and only works for one link type
(struct_ops) is not very convincing.
Beside, I am not sure how the file flags (e.g. rdonly...etc) should be handled.
I don't know enough in this area, so I will defer to others to comment in
general the usefulness and the approach.
