[PATCH v4 24/25] mm/filemap: Convert page wait queues to be folios

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

Reinforce that if we're waiting for a bit in a struct page, that's
actually in the head page by changing the type from page to folio.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/pagemap.h |  6 +++---
 mm/filemap.c            | 30 ++++++++++++++++--------------
 2 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 6ee4bc843f98..2236f726bf01 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -611,13 +611,13 @@ static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 
 /* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
 struct wait_page_key {
-	struct page *page;
+	struct folio *folio;
 	int bit_nr;
 	int page_match;
 };
 
 struct wait_page_queue {
-	struct page *page;
+	struct folio *folio;
 	int bit_nr;
 	wait_queue_entry_t wait;
 };
@@ -625,7 +625,7 @@ struct wait_page_queue {
 static inline bool wake_page_match(struct wait_page_queue *wait_page,
 				  struct wait_page_key *key)
 {
-	if (wait_page->page != key->page)
+	if (wait_page->folio != key->folio)
 	       return false;
 	key->page_match = 1;
 
diff --git a/mm/filemap.c b/mm/filemap.c
index 57f46ff2f230..1cdd565c69a6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -992,11 +992,11 @@ EXPORT_SYMBOL(__page_cache_alloc);
  */
 #define PAGE_WAIT_TABLE_BITS 8
 #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
-static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
+static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
 
-static wait_queue_head_t *page_waitqueue(struct page *page)
+static wait_queue_head_t *folio_waitqueue(struct folio *folio)
 {
-	return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
+	return &folio_wait_table[hash_ptr(folio, PAGE_WAIT_TABLE_BITS)];
 }
 
 void __init pagecache_init(void)
@@ -1004,7 +1004,7 @@ void __init pagecache_init(void)
 	int i;
 
 	for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
-		init_waitqueue_head(&page_wait_table[i]);
+		init_waitqueue_head(&folio_wait_table[i]);
 
 	page_writeback_init();
 }
@@ -1059,10 +1059,11 @@ static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync,
 	 */
 	flags = wait->flags;
 	if (flags & WQ_FLAG_EXCLUSIVE) {
-		if (test_bit(key->bit_nr, &key->page->flags))
+		if (test_bit(key->bit_nr, &key->folio->page.flags))
 			return -1;
 		if (flags & WQ_FLAG_CUSTOM) {
-			if (test_and_set_bit(key->bit_nr, &key->page->flags))
+			if (test_and_set_bit(key->bit_nr,
+						&key->folio->page.flags))
 				return -1;
 			flags |= WQ_FLAG_DONE;
 		}
@@ -1096,12 +1097,12 @@ static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync,
 
 static void wake_up_folio_bit(struct folio *folio, int bit_nr)
 {
-	wait_queue_head_t *q = page_waitqueue(&folio->page);
+	wait_queue_head_t *q = folio_waitqueue(folio);
 	struct wait_page_key key;
 	unsigned long flags;
 	wait_queue_entry_t bookmark;
 
-	key.page = &folio->page;
+	key.folio = folio;
 	key.bit_nr = bit_nr;
 	key.page_match = 0;
 
@@ -1193,7 +1194,7 @@ int sysctl_page_lock_unfairness = 5;
 static inline int wait_on_folio_bit_common(struct folio *folio, int bit_nr,
 		int state, enum behavior behavior)
 {
-	wait_queue_head_t *q = page_waitqueue(&folio->page);
+	wait_queue_head_t *q = folio_waitqueue(folio);
 	int unfairness = sysctl_page_lock_unfairness;
 	struct wait_page_queue wait_page;
 	wait_queue_entry_t *wait = &wait_page.wait;
@@ -1213,7 +1214,7 @@ static inline int wait_on_folio_bit_common(struct folio *folio, int bit_nr,
 
 	init_wait(wait);
 	wait->func = wake_page_function;
-	wait_page.page = &folio->page;
+	wait_page.folio = folio;
 	wait_page.bit_nr = bit_nr;
 
 repeat:
@@ -1370,12 +1371,13 @@ int put_and_wait_on_page_locked(struct page *page, int state)
  */
 void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
 {
-	wait_queue_head_t *q = page_waitqueue(page);
+	struct folio *folio = page_folio(page);
+	wait_queue_head_t *q = folio_waitqueue(folio);
 	unsigned long flags;
 
 	spin_lock_irqsave(&q->lock, flags);
 	__add_wait_queue_entry_tail(q, waiter);
-	SetPageWaiters(page);
+	SetFolioWaiters(folio);
 	spin_unlock_irqrestore(&q->lock, flags);
 }
 EXPORT_SYMBOL_GPL(add_page_wait_queue);
@@ -1503,10 +1505,10 @@ EXPORT_SYMBOL_GPL(__lock_folio_killable);
 
 int __lock_folio_async(struct folio *folio, struct wait_page_queue *wait)
 {
-	struct wait_queue_head *q = page_waitqueue(&folio->page);
+	struct wait_queue_head *q = folio_waitqueue(folio);
 	int ret = 0;
 
-	wait->page = &folio->page;
+	wait->folio = folio;
 	wait->bit_nr = PG_locked;
 
 	spin_lock_irq(&q->lock);
-- 
2.30.0