fs: Add invalidate_folio() aops method

This is used in preference to invalidatepage, if defined.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Mike Marshall <hubcap@omnibond.com> # orangefs
Tested-by: David Howells <dhowells@redhat.com> # afs

Documentation/filesystems/locking.rst

@@ -250,6 +250,7 @@ prototypes::
 				loff_t pos, unsigned len, unsigned copied,
 				struct page *page, void *fsdata);
 	sector_t (*bmap)(struct address_space *, sector_t);
+	void (*invalidate_folio) (struct folio *, size_t start, size_t len);
 	void (*invalidatepage) (struct page *, unsigned int, unsigned int);
 	int (*releasepage) (struct page *, int);
 	void (*freepage)(struct page *);
@@ -278,6 +279,7 @@ readpages:		no					shared
 write_begin:		locks the page		 exclusive
 write_end:		yes, unlocks		 exclusive
 bmap:
+invalidate_folio:	yes					exclusive
 invalidatepage:		yes					exclusive
 releasepage:		yes
 freepage:		yes
@@ -370,13 +372,12 @@ not locked.
 filesystems and by the swapper. The latter will eventually go away.  Please,
 keep it that way and don't breed new callers.
 
-->invalidatepage() is called when the filesystem must attempt to drop
+->invalidate_folio() is called when the filesystem must attempt to drop
 some or all of the buffers from the page when it is being truncated. It
-returns zero on success. If ->invalidatepage is zero, the kernel uses
-block_invalidatepage() instead. The filesystem must exclusively acquire
-invalidate_lock before invalidating page cache in truncate / hole punch path
-(and thus calling into ->invalidatepage) to block races between page cache
-invalidation and page cache filling functions (fault, read, ...).
+returns zero on success.  The filesystem must exclusively acquire
+invalidate_lock before invalidating page cache in truncate / hole punch
+path (and thus calling into ->invalidate_folio) to block races between page
+cache invalidation and page cache filling functions (fault, read, ...).
 
 ->releasepage() is called when the kernel is about to try to drop the
 buffers from the page in preparation for freeing it.  It returns zero to

Documentation/filesystems/vfs.rst

@@ -735,6 +735,7 @@ cache in your filesystem.  The following members are defined:
 				 loff_t pos, unsigned len, unsigned copied,
 				 struct page *page, void *fsdata);
 		sector_t (*bmap)(struct address_space *, sector_t);
+		void (*invalidate_folio) (struct folio *, size_t start, size_t len);
 		void (*invalidatepage) (struct page *, unsigned int, unsigned int);
 		int (*releasepage) (struct page *, int);
 		void (*freepage)(struct page *);
@@ -868,15 +869,15 @@ cache in your filesystem.  The following members are defined:
 	to find out where the blocks in the file are and uses those
 	addresses directly.
 
-``invalidatepage``
-	If a page has PagePrivate set, then invalidatepage will be
-	called when part or all of the page is to be removed from the
+``invalidate_folio``
+	If a folio has private data, then invalidate_folio will be
+	called when part or all of the folio is to be removed from the
 	address space.  This generally corresponds to either a
 	truncation, punch hole or a complete invalidation of the address
 	space (in the latter case 'offset' will always be 0 and 'length'
-	will be PAGE_SIZE).  Any private data associated with the page
+	will be folio_size()).  Any private data associated with the page
 	should be updated to reflect this truncation.  If offset is 0
-	and length is PAGE_SIZE, then the private data should be
+	and length is folio_size(), then the private data should be
 	released, because the page must be able to be completely
 	discarded.  This may be done by calling the ->releasepage
 	function, but in this case the release MUST succeed.

include/linux/fs.h

@@ -387,6 +387,7 @@ struct address_space_operations {
 
 	/* Unfortunately this kludge is needed for FIBMAP. Don't use it */
 	sector_t (*bmap)(struct address_space *, sector_t);
+	void (*invalidate_folio) (struct folio *, size_t offset, size_t len);
 	void (*invalidatepage) (struct page *, unsigned int, unsigned int);
 	int (*releasepage) (struct page *, gfp_t);
 	void (*freepage)(struct page *);

mm/truncate.c

@@ -154,9 +154,15 @@ static int invalidate_exceptional_entry2(struct address_space *mapping,
  */
 void folio_invalidate(struct folio *folio, size_t offset, size_t length)
 {
+	const struct address_space_operations *aops = folio->mapping->a_ops;
 	void (*invalidatepage)(struct page *, unsigned int, unsigned int);
 
-	invalidatepage = folio->mapping->a_ops->invalidatepage;
+	if (aops->invalidate_folio) {
+		aops->invalidate_folio(folio, offset, length);
+		return;
+	}
+
+	invalidatepage = aops->invalidatepage;
 #ifdef CONFIG_BLOCK
 	if (!invalidatepage)
 		invalidatepage = block_invalidatepage;