iomap: add a IOMAP_DIO_OVERWRITE_ONLY flag

Add a flag to signal that only pure overwrites are allowed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index be4e1e1e01e8..1a86f520de56 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -122,6 +122,7 @@ struct iomap_page_ops {
 #define IOMAP_FAULT		(1 << 3) /* mapping for page fault */
 #define IOMAP_DIRECT		(1 << 4) /* direct I/O */
 #define IOMAP_NOWAIT		(1 << 5) /* do not block */
+#define IOMAP_OVERWRITE_ONLY	(1 << 6) /* only pure overwrites allowed */
 
 struct iomap_ops {
 	/*
@@ -262,6 +263,13 @@ struct iomap_dio_ops {
  */
 #define IOMAP_DIO_FORCE_WAIT	(1 << 0)
 
+/*
+ * Do not allocate blocks or zero partial blocks, but instead fall back to
+ * the caller by returning -EAGAIN.  Used to optimize direct I/O writes that
+ * are not aligned to the file system block size.
+  */
+#define IOMAP_DIO_OVERWRITE_ONLY	(1 << 1)
+
 ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 		const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
 		unsigned int dio_flags);