On 11.07.24 06:32, Jason A. Donenfeld wrote:
On Thu, Jul 11, 2024 at 02:44:29AM +0200, Jason A. Donenfeld wrote:
Hi David,
On Wed, Jul 10, 2024 at 06:05:34AM +0200, David Hildenbrand wrote:
BTW, do we have to handle the folio_set_swapbacked() in sort_folio() as well?
/* dirty lazyfree */
if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) {
success = lru_gen_del_folio(lruvec, folio, true);
VM_WARN_ON_ONCE_FOLIO(!success, folio);
folio_set_swapbacked(folio);
lruvec_add_folio_tail(lruvec, folio);
return true;
}
Maybe more difficult because we don't have a VMA here ... hmm
IIUC, we have to make sure that no folio_set_swapbacked() would ever get
performed on these folios, correct?
Hmmm, I'm trying to figure out what to do here, and if we have to do
something. All three conditions in that if statement will be true for a
folio in a droppable mapping. That's supposed to match MADV_FREE
mappings.
What is the context of this, though? It's scanning pages for good ones
to evict into swap, right? So if it encounters one that's an MADV_FREE
page, it actually just wants to delete it, rather than sending it to
swap. So it looks like it does just that, and then sets the swapbacked
bit back to true, in case the folio is used for something differnet
later?
If that's correct, then I don't think we need to do anything for this
one.
If that's not correct, then we'll need to propagate the droppableness
to the folio level. But hopefully we don't need to do that.
Looks like that's not correct. This is for pages that have been dirtied
since calling MADV_FREE. So, hm.
Maybe we can find ways of simply never marking these pages dirty, so we
don't have to special-case that code where we don't really have a VMA at
hand?
--
Cheers,
David / dhildenb
