On Thu, Dec 08, 2022 at 12:28:07PM -0800, Nhat Pham wrote:
> + struct address_space *mapping = f.file->f_mapping;
> + pgoff_t first_index = off >> PAGE_SHIFT;
> + pgoff_t last_index =
> + len == 0 ? ULONG_MAX : (off + len - 1) >> PAGE_SHIFT;
> + XA_STATE(xas, &mapping->i_pages, first_index);
> + struct folio *folio;
> +
> + rcu_read_lock();
> + xas_for_each(&xas, folio, last_index) {
> + if (xas_retry(&xas, folio) || !folio)
> + continue;
!folio can't be true. xas_for_each() terminates when folio is NULL.
> + if (xa_is_value(folio)) {
> + /* page is evicted */
> + void *shadow = (void *)folio;
> + bool workingset; /* not used */
> +
> + cs.nr_evicted += 1;
> +
> +#ifdef CONFIG_SWAP /* implies CONFIG_MMU */
> + if (shmem_mapping(mapping)) {
> + /* shmem file - in swap cache */
> + swp_entry_t swp = radix_to_swp_entry(folio);
> +
> + shadow = get_shadow_from_swap_cache(swp);
> + }
> +#endif
> + if (workingset_test_recent(shadow, true, &workingset))
> + cs.nr_recently_evicted += 1;
> +
> + continue;
> + }
> +
> + /* page is in cache */
> + cs.nr_cache += 1;
> +
> + if (folio_test_dirty(folio))
> + cs.nr_dirty += 1;
> +
> + if (folio_test_writeback(folio))
> + cs.nr_writeback += 1;
A folio may represent more than one page. That's the point of folios.
So there should be something in here which does
unsigned long nr = folio_nr_pages();
and then all these '1' should be 'nr'.
Except that you may need to adjust nr if 'first_index' > folio->index, or
'last_index' < folio->index + nr.
You should test this with XFS, AFS or erofs to be sure you're getting
results that look right.
