iomap: add read_folio_range() handler for buffered writes

Add a read_folio_range() handler for buffered writes that filesystems
may pass in if they wish to provide a custom handler for synchronously
reading in the contents of a folio.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
[hch: renamed to read_folio_range, pass less arguments]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/20250710133343.399917-14-hch@lst.de
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 80f543cc4fe8..73dceabc21c8 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -166,6 +166,16 @@ struct iomap_write_ops {
 	 * locked by the iomap code.
 	 */
 	bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap);
+
+	/*
+	 * Optional if the filesystem wishes to provide a custom handler for
+	 * reading in the contents of a folio, otherwise iomap will default to
+	 * submitting a bio read request.
+	 *
+	 * The read must be done synchronously.
+	 */
+	int (*read_folio_range)(const struct iomap_iter *iter,
+			struct folio *folio, loff_t pos, size_t len);
 };
 
 /*