Add a flag to signal an only pure overwrites are allowed.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/iomap/direct-io.c | 7 +++++++
include/linux/iomap.h | 8 ++++++++
2 files changed, 15 insertions(+)
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 947343730e2c93..65d32364345d22 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -485,6 +485,13 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
iomap_flags |= IOMAP_NOWAIT;
}
+ if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
+ ret = -EAGAIN;
+ if (pos >= dio->i_size || pos + count > dio->i_size)
+ goto out_free_dio;
+ iomap_flags |= IOMAP_OVERWRITE_ONLY;
+ }
+
ret = filemap_write_and_wait_range(mapping, pos, end);
if (ret)
goto out_free_dio;
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index be4e1e1e01e801..cfa20afd7d5b87 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) /* purely 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);
--
2.29.2
