fsdax: dedupe: iter two files at the same time

The iomap_iter() on a range of one file may loop more than once.  In this
case, the inner dst_iter can update its iomap but the outer src_iter
can't.  This may cause the wrong remapping in filesystem.  Let them called
at the same time.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Shiyang Ruan <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: John Hubbard <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 8 insertions, 8 deletions

diff --git a/fs/dax.c b/fs/dax.c
index fa547ce41add..8fb928cd9dce 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1965,15 +1965,15 @@ int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
 		.len		= len,
 		.flags		= IOMAP_DAX,
 	};
-	int ret;
+	int ret, compared = 0;
 
-	while ((ret = iomap_iter(&src_iter, ops)) > 0) {
-		while ((ret = iomap_iter(&dst_iter, ops)) > 0) {
-			dst_iter.processed = dax_range_compare_iter(&src_iter,
-						&dst_iter, len, same);
-		}
-		if (ret <= 0)
-			src_iter.processed = ret;
+	while ((ret = iomap_iter(&src_iter, ops)) > 0 &&
+	       (ret = iomap_iter(&dst_iter, ops)) > 0) {
+		compared = dax_range_compare_iter(&src_iter, &dst_iter, len,
+						  same);
+		if (compared < 0)
+			return ret;
+		src_iter.processed = dst_iter.processed = compared;
 	}
 	return ret;
 }