On Wed, Oct 2, 2024 at 11:09 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
[...]
> +
> + mutex_lock(&slab_mutex);
> +
> + /*
> + * Find an entry at the given position in the slab_caches list instead
Nit: style of multi-line comment: "/* Find ...".
> + * of keeping a reference (of the last visited entry, if any) out of
> + * slab_mutex. It might miss something if one is deleted in the middle
> + * while it releases the lock. But it should be rare and there's not
> + * much we can do about it.
> + */
> + list_for_each_entry(s, &slab_caches, list) {
> + if (cnt == *pos) {
> + /*
> + * Make sure this entry remains in the list by getting
> + * a new reference count. Note that boot_cache entries
> + * have a negative refcount, so don't touch them.
> + */
> + if (s->refcount > 0)
> + s->refcount++;
> + found = true;
> + break;
> + }
> + cnt++;
> + }
> + mutex_unlock(&slab_mutex);
> +
> + if (!found)
> + return NULL;
> +
> + ++*pos;
> + return s;
> +}
> +
> +static void kmem_cache_iter_seq_stop(struct seq_file *seq, void *v)
> +{
> + struct bpf_iter_meta meta;
> + struct bpf_iter__kmem_cache ctx = {
> + .meta = &meta,
> + .s = v,
> + };
> + struct bpf_prog *prog;
> + bool destroy = false;
> +
> + meta.seq = seq;
> + prog = bpf_iter_get_info(&meta, true);
> + if (prog)
> + bpf_iter_run_prog(prog, &ctx);
> +
> + if (ctx.s == NULL)
> + return;
> +
> + mutex_lock(&slab_mutex);
> +
> + /* Skip kmem_cache_destroy() for active entries */
> + if (ctx.s->refcount > 1)
> + ctx.s->refcount--;
> + else if (ctx.s->refcount == 1)
> + destroy = true;
> +
> + mutex_unlock(&slab_mutex);
> +
> + if (destroy)
> + kmem_cache_destroy(ctx.s);
> +}
> +
> +static void *kmem_cache_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos)
> +{
> + struct kmem_cache *s = v;
> + struct kmem_cache *next = NULL;
> + bool destroy = false;
> +
> + ++*pos;
> +
> + mutex_lock(&slab_mutex);
> +
> + if (list_last_entry(&slab_caches, struct kmem_cache, list) != s) {
> + next = list_next_entry(s, list);
> + if (next->refcount > 0)
> + next->refcount++;
What if next->refcount <=0? Shall we find next of next?
> + }
> +
> + /* Skip kmem_cache_destroy() for active entries */
> + if (s->refcount > 1)
> + s->refcount--;
> + else if (s->refcount == 1)
> + destroy = true;
> +
> + mutex_unlock(&slab_mutex);
> +
> + if (destroy)
> + kmem_cache_destroy(s);
> +
> + return next;
> +}
[...]
