Commit 2fad3d14 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

huge_memory: convert do_huge_pmd_wp_page() to use a folio 

Removes many calls to compound_head().  Does not remove the assumption
that a folio may not be larger than a PMD.

Link: https://lkml.kernel.org/r/20220902194653.1739778-43-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e4a2ed94

mm/huge_memory.c

+19 −16
Original line number Diff line number Diff line
@@ -1305,6 +1305,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) 
{

	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;

	struct vm_area_struct *vma = vmf->vma;

	struct folio *folio;

	struct page *page;

	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;

	pmd_t orig_pmd = vmf->orig_pmd;
@@ -1326,46 +1327,48 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) 
	}



	page = pmd_page(orig_pmd);

	folio = page_folio(page);

	VM_BUG_ON_PAGE(!PageHead(page), page);



	/* Early check when only holding the PT lock. */

	if (PageAnonExclusive(page))

		goto reuse;



	if (!trylock_page(page)) {

		get_page(page);

	if (!folio_trylock(folio)) {

		folio_get(folio);

		spin_unlock(vmf->ptl);

		lock_page(page);

		folio_lock(folio);

		spin_lock(vmf->ptl);

		if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {

			spin_unlock(vmf->ptl);

			unlock_page(page);

			put_page(page);

			folio_unlock(folio);

			folio_put(folio);

			return 0;

		}

		put_page(page);

		folio_put(folio);

	}



	/* Recheck after temporarily dropping the PT lock. */

	if (PageAnonExclusive(page)) {

		unlock_page(page);

		folio_unlock(folio);

		goto reuse;

	}



	/*

	 * See do_wp_page(): we can only reuse the page exclusively if there are

	 * no additional references. Note that we always drain the LRU

	 * pagevecs immediately after adding a THP.

	 * See do_wp_page(): we can only reuse the folio exclusively if

	 * there are no additional references. Note that we always drain

	 * the LRU pagevecs immediately after adding a THP.

	 */

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

	if (folio_ref_count(folio) >

			1 + folio_test_swapcache(folio) * folio_nr_pages(folio))

		goto unlock_fallback;

	if (PageSwapCache(page))

		try_to_free_swap(page);

	if (page_count(page) == 1) {

	if (folio_test_swapcache(folio))

		folio_free_swap(folio);

	if (folio_ref_count(folio) == 1) {

		pmd_t entry;



		page_move_anon_rmap(page, vma);

		unlock_page(page);

		folio_unlock(folio);

reuse:

		if (unlikely(unshare)) {

			spin_unlock(vmf->ptl);
@@ -1380,7 +1383,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) 
	}



unlock_fallback:

	unlock_page(page);

	folio_unlock(folio);

	spin_unlock(vmf->ptl);

fallback:

	__split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);