fs: Add free_folio address space operation

Include documentation and convert the callers to use ->free_folio as
well as ->freepage.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Documentation/filesystems/locking.rst

@@ -250,7 +250,7 @@ prototypes::
 	sector_t (*bmap)(struct address_space *, sector_t);
 	void (*invalidate_folio) (struct folio *, size_t start, size_t len);
 	bool (*release_folio)(struct folio *, gfp_t);
-	void (*freepage)(struct page *);
+	void (*free_folio)(struct folio *);
 	int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 	bool (*isolate_page) (struct page *, isolate_mode_t);
 	int (*migratepage)(struct address_space *, struct page *, struct page *);
@@ -262,10 +262,10 @@ prototypes::
 	int (*swap_deactivate)(struct file *);
 
 locking rules:
-	All except dirty_folio and freepage may block
+	All except dirty_folio and free_folio may block
 
 ======================	======================== =========	===============
-ops			PageLocked(page)	 i_rwsem	invalidate_lock
+ops			folio locked		 i_rwsem	invalidate_lock
 ======================	======================== =========	===============
 writepage:		yes, unlocks (see below)
 read_folio:		yes, unlocks				shared
@@ -277,7 +277,7 @@ write_end:		yes, unlocks		 exclusive
 bmap:
 invalidate_folio:	yes					exclusive
 release_folio:		yes
-freepage:		yes
+free_folio:		yes
 direct_IO:
 isolate_page:		yes
 migratepage:		yes (both)
@@ -377,7 +377,7 @@ buffers from the folio in preparation for freeing it.  It returns false to
 indicate that the buffers are (or may be) freeable.  If ->release_folio is
 NULL, the kernel assumes that the fs has no private interest in the buffers.
 
-->freepage() is called when the kernel is done dropping the page
+->free_folio() is called when the kernel has dropped the folio
 from the page cache.
 
 ->launder_folio() may be called prior to releasing a folio if

Documentation/filesystems/vfs.rst

@@ -735,7 +735,7 @@ cache in your filesystem.  The following members are defined:
 		sector_t (*bmap)(struct address_space *, sector_t);
 		void (*invalidate_folio) (struct folio *, size_t start, size_t len);
 		bool (*release_folio)(struct folio *, gfp_t);
-		void (*freepage)(struct page *);
+		void (*free_folio)(struct folio *);
 		ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 		/* isolate a page for migration */
 		bool (*isolate_page) (struct page *, isolate_mode_t);
@@ -891,8 +891,8 @@ cache in your filesystem.  The following members are defined:
 	its release_folio will need to ensure this.  Possibly it can
 	clear the uptodate flag if it cannot free private data yet.
 
-``freepage``
-	freepage is called once the page is no longer visible in the
+``free_folio``
+	free_folio is called once the folio is no longer visible in the
 	page cache in order to allow the cleanup of any private data.
 	Since it may be called by the memory reclaimer, it should not
 	assume that the original address_space mapping still exists, and

include/linux/fs.h

@@ -356,6 +356,7 @@ struct address_space_operations {
 	sector_t (*bmap)(struct address_space *, sector_t);
 	void (*invalidate_folio) (struct folio *, size_t offset, size_t len);
 	bool (*release_folio)(struct folio *, gfp_t);
+	void (*free_folio)(struct folio *folio);
 	void (*freepage)(struct page *);
 	ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 	/*

mm/filemap.c

@@ -226,8 +226,12 @@ void __filemap_remove_folio(struct folio *folio, void *shadow)
 void filemap_free_folio(struct address_space *mapping, struct folio *folio)
 {
 	void (*freepage)(struct page *);
+	void (*free_folio)(struct folio *);
 	int refs = 1;
 
+	free_folio = mapping->a_ops->free_folio;
+	if (free_folio)
+		free_folio(folio);
 	freepage = mapping->a_ops->freepage;
 	if (freepage)
 		freepage(&folio->page);
@@ -807,6 +811,7 @@ void replace_page_cache_page(struct page *old, struct page *new)
 	struct folio *fold = page_folio(old);
 	struct folio *fnew = page_folio(new);
 	struct address_space *mapping = old->mapping;
+	void (*free_folio)(struct folio *) = mapping->a_ops->free_folio;
 	void (*freepage)(struct page *) = mapping->a_ops->freepage;
 	pgoff_t offset = old->index;
 	XA_STATE(xas, &mapping->i_pages, offset);
@@ -835,9 +840,11 @@ void replace_page_cache_page(struct page *old, struct page *new)
 	if (PageSwapBacked(new))
 		__inc_lruvec_page_state(new, NR_SHMEM);
 	xas_unlock_irq(&xas);
+	if (free_folio)
+		free_folio(fold);
 	if (freepage)
 		freepage(old);
-	put_page(old);
+	folio_put(fold);
 }
 EXPORT_SYMBOL_GPL(replace_page_cache_page);
 

mm/vmscan.c

@@ -1282,8 +1282,10 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
 		xa_unlock_irq(&mapping->i_pages);
 		put_swap_page(&folio->page, swap);
 	} else {
+		void (*free_folio)(struct folio *);
 		void (*freepage)(struct page *);
 
+		free_folio = mapping->a_ops->free_folio;
 		freepage = mapping->a_ops->freepage;
 		/*
 		 * Remember a shadow entry for reclaimed file cache in
@@ -1310,7 +1312,9 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
 			inode_add_lru(mapping->host);
 		spin_unlock(&mapping->host->i_lock);
 
-		if (freepage != NULL)
+		if (free_folio)
+			free_folio(folio);
+		if (freepage)
 			freepage(&folio->page);
 	}