Commit e4a2ed94 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

mm: convert do_wp_page() to use a folio 

Saves many calls to compound_head().

Link: https://lkml.kernel.org/r/20220902194653.1739778-42-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 71fa1a53

mm/memory.c

+20 −20
Original line number Diff line number Diff line
@@ -3368,6 +3368,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) 
{

	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;

	struct vm_area_struct *vma = vmf->vma;

	struct folio *folio;



	VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE));

	VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE));
@@ -3414,48 +3415,47 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) 
	 * Take out anonymous pages first, anonymous shared vmas are

	 * not dirty accountable.

	 */

	if (PageAnon(vmf->page)) {

		struct page *page = vmf->page;



	folio = page_folio(vmf->page);

	if (folio_test_anon(folio)) {

		/*

		 * If the page is exclusive to this process we must reuse the

		 * page without further checks.

		 */

		if (PageAnonExclusive(page))

		if (PageAnonExclusive(vmf->page))

			goto reuse;



		/*

		 * We have to verify under page lock: these early checks are

		 * just an optimization to avoid locking the page and freeing

		 * We have to verify under folio lock: these early checks are

		 * just an optimization to avoid locking the folio and freeing

		 * the swapcache if there is little hope that we can reuse.

		 *

		 * PageKsm() doesn't necessarily raise the page refcount.

		 * KSM doesn't necessarily raise the folio refcount.

		 */

		if (PageKsm(page) || page_count(page) > 3)

		if (folio_test_ksm(folio) || folio_ref_count(folio) > 3)

			goto copy;

		if (!PageLRU(page))

		if (!folio_test_lru(folio))

			/*

			 * Note: We cannot easily detect+handle references from

			 * remote LRU pagevecs or references to PageLRU() pages.

			 * remote LRU pagevecs or references to LRU folios.

			 */

			lru_add_drain();

		if (page_count(page) > 1 + PageSwapCache(page))

		if (folio_ref_count(folio) > 1 + folio_test_swapcache(folio))

			goto copy;

		if (!trylock_page(page))

		if (!folio_trylock(folio))

			goto copy;

		if (PageSwapCache(page))

			try_to_free_swap(page);

		if (PageKsm(page) || page_count(page) != 1) {

			unlock_page(page);

		if (folio_test_swapcache(folio))

			folio_free_swap(folio);

		if (folio_test_ksm(folio) || folio_ref_count(folio) != 1) {

			folio_unlock(folio);

			goto copy;

		}

		/*

		 * Ok, we've got the only page reference from our mapping

		 * and the page is locked, it's dark out, and we're wearing

		 * Ok, we've got the only folio reference from our mapping

		 * and the folio is locked, it's dark out, and we're wearing

		 * sunglasses. Hit it.

		 */

		page_move_anon_rmap(page, vma);

		unlock_page(page);

		page_move_anon_rmap(vmf->page, vma);

		folio_unlock(folio);

reuse:

		if (unlikely(unshare)) {

			pte_unmap_unlock(vmf->pte, vmf->ptl);