On 14.07.23 18:17, Ryan Roberts wrote:
In preparation for FLEXIBLE_THP support, improve
folio_add_new_anon_rmap() to allow a non-pmd-mappable, large folio to be
passed to it. In this case, all contained pages are accounted using the
order-0 folio (or base page) scheme.
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Reviewed-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Reviewed-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
---
mm/rmap.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 0c0d8857dfce..f293d072368a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1278,31 +1278,45 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
* This means the inc-and-test can be bypassed.
* The folio does not have to be locked.
*
- * If the folio is large, it is accounted as a THP. As the folio
+ * If the folio is pmd-mappable, it is accounted as a THP. As the folio
* is new, it's assumed to be mapped exclusively by a single process.
*/
void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
unsigned long address)
{
- int nr;
+ int nr = folio_nr_pages(folio);
- VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
+ VM_BUG_ON_VMA(address < vma->vm_start ||
+ address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
__folio_set_swapbacked(folio);
- if (likely(!folio_test_pmd_mappable(folio))) {
+ if (!folio_test_large(folio)) {
Why remove the "likely" here? The patch itself does not change anything
about that condition.
/* increment count (starts at -1) */
atomic_set(&folio->_mapcount, 0);
- nr = 1;
+ __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
+ } else if (!folio_test_pmd_mappable(folio)) {
+ int i;
+
+ for (i = 0; i < nr; i++) {
+ struct page *page = folio_page(folio, i);
+
+ /* increment count (starts at -1) */
+ atomic_set(&page->_mapcount, 0);
+ __page_set_anon_rmap(folio, page, vma,
+ address + (i << PAGE_SHIFT), 1);
+ }
+
+ /* increment count (starts at 0) */
That comment is a bit misleading. We're not talking about a mapcount as
in the other cases here.
+ atomic_set(&folio->_nr_pages_mapped, nr);
} else {
/* increment count (starts at -1) */
atomic_set(&folio->_entire_mapcount, 0);
atomic_set(&folio->_nr_pages_mapped, COMPOUND_MAPPED);
- nr = folio_nr_pages(folio);
+ __page_set_anon_rmap(folio, &folio->page, vma, address, 1);
__lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr);
}
Apart from that, LGTM.
--
Cheers,
David / dhildenb
