dax: advance the iomap_iter in the read/write path

DAX reads and writes flow through dax_iomap_iter(), which has one or
more subtleties in terms of how it processes a range vs. what is
specified in the iomap_iter. To keep things simple and remove the
dependency on iomap_iter() advances, convert a positive return from
dax_iomap_iter() to the new advance and status return semantics. The
advance can be pushed further down in future patches.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Link: https://lore.kernel.org/r/20250224144757.237706-5-bfoster@redhat.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 21b47402b3dc..296f5aa18640 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1585,8 +1585,12 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 	if (iocb->ki_flags & IOCB_NOWAIT)
 		iomi.flags |= IOMAP_NOWAIT;
 
-	while ((ret = iomap_iter(&iomi, ops)) > 0)
+	while ((ret = iomap_iter(&iomi, ops)) > 0) {
 		iomi.processed = dax_iomap_iter(&iomi, iter);
+		if (iomi.processed > 0)
+			iomi.processed = iomap_iter_advance(&iomi,
+							    &iomi.processed);
+	}
 
 	done = iomi.pos - iocb->ki_pos;
 	iocb->ki_pos = iomi.pos;