On 22.11.24 02:40, Alistair Popple wrote:
Currently DAX folio/page reference counts are managed differently to
normal pages. To allow these to be managed the same as normal pages
introduce vmf_insert_folio_pud. This will map the entire PUD-sized folio
and take references as it would for a normally mapped page.
This is distinct from the current mechanism, vmf_insert_pfn_pud, which
simply inserts a special devmap PUD entry into the page table without
holding a reference to the page for the mapping.
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
---
Hi,
The patch subject of this (and especially the next patch) is misleading.
Likely you meant to have it as:
"mm/huge_memory: add vmf_insert_folio_pud() for mapping PUD sized pages"
for (i = 0; i < nr_pages; i++) {
@@ -1523,6 +1531,26 @@ void folio_add_file_rmap_pmd(struct folio *folio, struct page *page,
#endif
}
+/**
+ * folio_add_file_rmap_pud - add a PUD mapping to a page range of a folio
+ * @folio: The folio to add the mapping to
+ * @page: The first page to add
+ * @vma: The vm area in which the mapping is added
+ *
+ * The page range of the folio is defined by [page, page + HPAGE_PUD_NR)
+ *
+ * The caller needs to hold the page table lock.
+ */
+void folio_add_file_rmap_pud(struct folio *folio, struct page *page,
+ struct vm_area_struct *vma)
+{
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+ __folio_add_file_rmap(folio, page, HPAGE_PUD_NR, vma, RMAP_LEVEL_PUD);
+#else
+ WARN_ON_ONCE(true);
+#endif
+}
+
static __always_inline void __folio_remove_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *vma,
enum rmap_level level)
@@ -1552,6 +1580,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
partially_mapped = nr && atomic_read(mapped);
break;
case RMAP_LEVEL_PMD:
+ case RMAP_LEVEL_PUD:
atomic_dec(&folio->_large_mapcount);
last = atomic_add_negative(-1, &folio->_entire_mapcount);
if (last) {
If you simply reuse that code (here and on the adding path), you will
end up effectively setting nr_pmdmapped to a very large value and
passing that into __folio_mod_stat().
There, we will adjust NR_SHMEM_PMDMAPPED/NR_FILE_PMDMAPPED, which is
wrong (it's PUD mapped ;) ).
It's probably best to split out the rmap changes from the other things
in this patch.
--
Cheers,
David / dhildenb
