On Mon, Feb 06, 2023 at 05:49:20PM +0100, David Hildenbrand wrote:
> We have
>
> + if (!cow) {
> + folio_add_file_rmap_range(folio, start, nr, vma, false);
> + add_mm_counter(vma->vm_mm, mm_counter_file(page), nr);
> + } else {
> + /*
> + * rmap code is not ready to handle COW with anonymous
> + * large folio yet. Capture and warn if large folio
> + * is given.
> + */
> + VM_WARN_ON_FOLIO(folio_test_large(folio), folio);
> + }
>
> now.
>
> What are we supposed to add instead on the else branch instead that would be
> correct in the future? Or not look weird?
Right now, I think this patch should look something like this.
diff --git a/mm/memory.c b/mm/memory.c
index 7a04a1130ec1..2f6173f83d8b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4257,15 +4257,18 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
}
#endif
-void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
+void set_pte_range(struct vm_fault *vmf, struct folio *folio,
+ struct page *page, unsigned int nr, unsigned long addr)
{
struct vm_area_struct *vma = vmf->vma;
bool uffd_wp = pte_marker_uffd_wp(vmf->orig_pte);
bool write = vmf->flags & FAULT_FLAG_WRITE;
bool prefault = vmf->address != addr;
pte_t entry;
+ unsigned int i;
- flush_icache_page(vma, page);
+ for (i = 0; i < nr; i++)
+ flush_icache_page(vma, page + i);
entry = mk_pte(page, vma->vm_page_prot);
if (prefault && arch_wants_old_prefaulted_pte())
@@ -4279,14 +4282,15 @@ void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
entry = pte_mkuffd_wp(entry);
/* copy-on-write page */
if (write && !(vma->vm_flags & VM_SHARED)) {
- inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, vma, addr);
- lru_cache_add_inactive_or_unevictable(page, vma);
+ add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr);
+ VM_BUG_ON_FOLIO(folio, nr != 1);
+ folio_add_new_anon_rmap(folio, vma, addr);
+ folio_add_lru_vma(folio, vma);
} else {
- inc_mm_counter(vma->vm_mm, mm_counter_file(page));
- page_add_file_rmap(page, vma, false);
+ add_mm_counter(vma->vm_mm, mm_counter_file(page), nr);
+ folio_add_file_rmap_range(folio, page, nr, vma, false);
}
- set_pte_at(vma->vm_mm, addr, vmf->pte, entry);
+ set_ptes(vma->vm_mm, addr, vmf->pte, entry, nr);
}
static bool vmf_pte_changed(struct vm_fault *vmf)
@@ -4359,7 +4363,9 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
/* Re-check under ptl */
if (likely(!vmf_pte_changed(vmf))) {
- do_set_pte(vmf, page, vmf->address);
+ struct folio *folio = page_folio(page);
+
+ set_pte_range(vmf, folio, page, 1, vmf->address);
/* no need to invalidate: a not-present page won't be cached */
update_mmu_cache(vma, vmf->address, vmf->pte);
> Go on, scream louder at me, I don't care.
I'm not even shouting. I just think you're wrong ;-)
