[PATCH 21/21] mm/shmem: Convert shmem_swapin_page() to shmem_swapin_folio()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

shmem_swapin_page() only brings in order-0 pages, which are folios
by definition.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 arch/arm64/include/asm/pgtable.h |   6 +-
 include/linux/pgtable.h          |   2 +-
 mm/shmem.c                       | 108 ++++++++++++++-----------------
 3 files changed, 54 insertions(+), 62 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index dff2b483ea50..27cb6a355fb0 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -964,10 +964,10 @@ static inline void arch_swap_invalidate_area(int type)
 }
 
 #define __HAVE_ARCH_SWAP_RESTORE
-static inline void arch_swap_restore(swp_entry_t entry, struct page *page)
+static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
 {
-	if (system_supports_mte() && mte_restore_tags(entry, page))
-		set_bit(PG_mte_tagged, &page->flags);
+	if (system_supports_mte() && mte_restore_tags(entry, &folio->page))
+		set_bit(PG_mte_tagged, &folio->flags);
 }
 
 #endif /* CONFIG_ARM64_MTE */
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index f4f4077b97aa..a1c44b015463 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -738,7 +738,7 @@ static inline void arch_swap_invalidate_area(int type)
 #endif
 
 #ifndef __HAVE_ARCH_SWAP_RESTORE
-static inline void arch_swap_restore(swp_entry_t entry, struct page *page)
+static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
 {
 }
 #endif
diff --git a/mm/shmem.c b/mm/shmem.c
index 7457f352cf9f..673a0e783496 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -134,8 +134,8 @@ static unsigned long shmem_default_max_inodes(void)
 }
 #endif
 
-static int shmem_swapin_page(struct inode *inode, pgoff_t index,
-			     struct page **pagep, enum sgp_type sgp,
+static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
+			     struct folio **foliop, enum sgp_type sgp,
 			     gfp_t gfp, struct vm_area_struct *vma,
 			     vm_fault_t *fault_type);
 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
@@ -1158,69 +1158,64 @@ static void shmem_evict_inode(struct inode *inode)
 }
 
 static int shmem_find_swap_entries(struct address_space *mapping,
-				   pgoff_t start, unsigned int nr_entries,
-				   struct page **entries, pgoff_t *indices,
-				   unsigned int type)
+				   pgoff_t start, struct folio_batch *fbatch,
+				   pgoff_t *indices, unsigned int type)
 {
 	XA_STATE(xas, &mapping->i_pages, start);
-	struct page *page;
+	struct folio *folio;
 	swp_entry_t entry;
 	unsigned int ret = 0;
 
-	if (!nr_entries)
-		return 0;
-
 	rcu_read_lock();
-	xas_for_each(&xas, page, ULONG_MAX) {
-		if (xas_retry(&xas, page))
+	xas_for_each(&xas, folio, ULONG_MAX) {
+		if (xas_retry(&xas, folio))
 			continue;
 
-		if (!xa_is_value(page))
+		if (!xa_is_value(folio))
 			continue;
 
-		entry = radix_to_swp_entry(page);
+		entry = radix_to_swp_entry(folio);
 		if (swp_type(entry) != type)
 			continue;
 
 		indices[ret] = xas.xa_index;
-		entries[ret] = page;
+		if (!folio_batch_add(fbatch, folio))
+			break;
 
 		if (need_resched()) {
 			xas_pause(&xas);
 			cond_resched_rcu();
 		}
-		if (++ret == nr_entries)
-			break;
 	}
 	rcu_read_unlock();
 
-	return ret;
+	return xas.xa_index;
 }
 
 /*
  * Move the swapped pages for an inode to page cache. Returns the count
  * of pages swapped in, or the error in case of failure.
  */
-static int shmem_unuse_swap_entries(struct inode *inode, struct pagevec pvec,
-				    pgoff_t *indices)
+static int shmem_unuse_swap_entries(struct inode *inode,
+		struct folio_batch *fbatch, pgoff_t *indices)
 {
 	int i = 0;
 	int ret = 0;
 	int error = 0;
 	struct address_space *mapping = inode->i_mapping;
 
-	for (i = 0; i < pvec.nr; i++) {
-		struct page *page = pvec.pages[i];
+	for (i = 0; i < folio_batch_count(fbatch); i++) {
+		struct folio *folio = fbatch->folios[i];
 
-		if (!xa_is_value(page))
+		if (!xa_is_value(folio))
 			continue;
-		error = shmem_swapin_page(inode, indices[i],
-					  &page, SGP_CACHE,
+		error = shmem_swapin_folio(inode, indices[i],
+					  &folio, SGP_CACHE,
 					  mapping_gfp_mask(mapping),
 					  NULL, NULL);
 		if (error == 0) {
-			unlock_page(page);
-			put_page(page);
+			folio_unlock(folio);
+			folio_put(folio);
 			ret++;
 		}
 		if (error == -ENOMEM)
@@ -1237,26 +1232,23 @@ static int shmem_unuse_inode(struct inode *inode, unsigned int type)
 {
 	struct address_space *mapping = inode->i_mapping;
 	pgoff_t start = 0;
-	struct pagevec pvec;
+	struct folio_batch fbatch;
 	pgoff_t indices[PAGEVEC_SIZE];
 	int ret = 0;
 
-	pagevec_init(&pvec);
 	do {
-		unsigned int nr_entries = PAGEVEC_SIZE;
-
-		pvec.nr = shmem_find_swap_entries(mapping, start, nr_entries,
-						  pvec.pages, indices, type);
-		if (pvec.nr == 0) {
+		folio_batch_init(&fbatch);
+		shmem_find_swap_entries(mapping, start, &fbatch, indices, type);
+		if (folio_batch_count(&fbatch) == 0) {
 			ret = 0;
 			break;
 		}
 
-		ret = shmem_unuse_swap_entries(inode, pvec, indices);
+		ret = shmem_unuse_swap_entries(inode, &fbatch, indices);
 		if (ret < 0)
 			break;
 
-		start = indices[pvec.nr - 1];
+		start = indices[folio_batch_count(&fbatch) - 1];
 	} while (true);
 
 	return ret;
@@ -1680,22 +1672,22 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
  * Returns 0 and the page in pagep if success. On failure, returns the
  * error code and NULL in *pagep.
  */
-static int shmem_swapin_page(struct inode *inode, pgoff_t index,
-			     struct page **pagep, enum sgp_type sgp,
+static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
+			     struct folio **foliop, enum sgp_type sgp,
 			     gfp_t gfp, struct vm_area_struct *vma,
 			     vm_fault_t *fault_type)
 {
 	struct address_space *mapping = inode->i_mapping;
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
-	struct page *page = NULL;
+	struct page *page;
 	struct folio *folio;
 	swp_entry_t swap;
 	int error;
 
-	VM_BUG_ON(!*pagep || !xa_is_value(*pagep));
-	swap = radix_to_swp_entry(*pagep);
-	*pagep = NULL;
+	VM_BUG_ON(!*foliop || !xa_is_value(*foliop));
+	swap = radix_to_swp_entry(*foliop);
+	*foliop = NULL;
 
 	/* Look it up and read it in.. */
 	page = lookup_swap_cache(swap, NULL, 0);
@@ -1713,27 +1705,28 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 			goto failed;
 		}
 	}
+	folio = page_folio(page);
 
 	/* We have to do this with page locked to prevent races */
-	lock_page(page);
-	if (!PageSwapCache(page) || page_private(page) != swap.val ||
+	folio_lock(folio);
+	if (!folio_test_swapcache(folio) ||
+	    folio_swap_entry(folio).val != swap.val ||
 	    !shmem_confirm_swap(mapping, index, swap)) {
 		error = -EEXIST;
 		goto unlock;
 	}
-	if (!PageUptodate(page)) {
+	if (!folio_test_uptodate(folio)) {
 		error = -EIO;
 		goto failed;
 	}
-	wait_on_page_writeback(page);
+	folio_wait_writeback(folio);
 
 	/*
 	 * Some architectures may have to restore extra metadata to the
-	 * physical page after reading from swap.
+	 * folio after reading from swap.
 	 */
-	arch_swap_restore(swap, page);
+	arch_swap_restore(swap, folio);
 
-	folio = page_folio(page);
 	if (shmem_should_replace_folio(folio, gfp)) {
 		error = shmem_replace_page(&page, gfp, info, index);
 		if (error)
@@ -1752,21 +1745,21 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	spin_unlock_irq(&info->lock);
 
 	if (sgp == SGP_WRITE)
-		mark_page_accessed(page);
+		folio_mark_accessed(folio);
 
-	delete_from_swap_cache(page);
-	set_page_dirty(page);
+	delete_from_swap_cache(&folio->page);
+	folio_mark_dirty(folio);
 	swap_free(swap);
 
-	*pagep = page;
+	*foliop = folio;
 	return 0;
 failed:
 	if (!shmem_confirm_swap(mapping, index, swap))
 		error = -EEXIST;
 unlock:
-	if (page) {
-		unlock_page(page);
-		put_page(page);
+	if (folio) {
+		folio_unlock(folio);
+		folio_put(folio);
 	}
 
 	return error;
@@ -1820,13 +1813,12 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	}
 
 	if (xa_is_value(folio)) {
-		struct page *page = &folio->page;
-		error = shmem_swapin_page(inode, index, &page,
+		error = shmem_swapin_folio(inode, index, &folio,
 					  sgp, gfp, vma, fault_type);
 		if (error == -EEXIST)
 			goto repeat;
 
-		*pagep = page;
+		*pagep = &folio->page;
 		return error;
 	}
 
-- 
2.34.1