iomap/gfs2: Get page in page_prepare handler

Change the iomap ->page_prepare() handler to get and return a locked
folio instead of doing that in iomap_write_begin().  This allows to
recover from out-of-memory situations in ->page_prepare(), which
eliminates the corresponding error handling code in iomap_write_begin().
The ->put_folio() handler now also isn't called with NULL as the folio
value anymore.

Filesystems are expected to use the iomap_get_folio() helper for getting
locked folios in their ->page_prepare() handlers.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 5 insertions, 4 deletions

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 188d14e786a4..d50501781856 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -13,6 +13,7 @@
 struct address_space;
 struct fiemap_extent_info;
 struct inode;
+struct iomap_iter;
 struct iomap_dio;
 struct iomap_writepage_ctx;
 struct iov_iter;
@@ -131,12 +132,12 @@ static inline bool iomap_inline_data_valid(const struct iomap *iomap)
  * associated with them.
  *
  * When page_prepare succeeds, put_folio will always be called to do any
- * cleanup work necessary.  In that put_folio call, @folio will be NULL if the
- * associated folio could not be obtained.  When folio is not NULL, put_folio
- * is responsible for unlocking and putting the folio.
+ * cleanup work necessary.  put_folio is responsible for unlocking and putting
+ * @folio.
  */
 struct iomap_page_ops {
-	int (*page_prepare)(struct inode *inode, loff_t pos, unsigned len);
+	struct folio *(*page_prepare)(struct iomap_iter *iter, loff_t pos,
+			unsigned len);
 	void (*put_folio)(struct inode *inode, loff_t pos, unsigned copied,
 			struct folio *folio);