Re: [RFC][PATCH 1/4] mm, page_owner: add folio allocate post callback for struct page_owner to make the owner clearer

Matthew Wilcox
2023-11-09T14:00:12Z

On Thu, Nov 09, 2023 at 11:25:18AM +0800, Jeff Xie wrote:
> adding a callback function in the struct page_owner to let the slab layer or the
> anon/file handler layer or any other memory-allocated layers to implement what
> they would like to tell.

There's no need to add a callback. We can tell what a folio is.

> + if (page_owner->folio_alloc_post_page_owner) {
> + rcu_read_lock();
> + tsk = find_task_by_pid_ns(page_owner->pid, &init_pid_ns);
> + rcu_read_unlock();
> + ret += page_owner->folio_alloc_post_page_owner(page_folio(page), tsk, page_owner->data,
> + kbuf + ret, count - ret);
> + } else
> + ret += scnprintf(kbuf + ret, count - ret, "OTHER_PAGE\n");

if (folio_test_slab(folio))
ret += slab_page_owner_info(folio, kbuf + ret, count - ret);
else if (folio_test_anon(folio))
ret += anon_page_owner_info(folio, kbuf + ret, count - ret);
else if (folio_test_movable(folio))
ret += null_page_owner_info(folio, kbuf + ret, count - ret);
else if (folio->mapping)
ret += file_page_owner_info(folio, kbuf + ret, count - ret);
else
ret += null_page_owner_info(folio, kbuf + ret, count - ret);

In this scenario, I have the anon handling ksm pages, but if that's not
desirable, we can add

else if (folio_test_ksm(folio))
ret += ksm_page_owner_info(folio, kbuf + ret, count - ret);

right before the folio_test_anon() clause