[PATCH v7 5/8] iomap: Introduce iomap_iter2 for two files

[Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>]

Some operations, such as comparing a range of data in two files under
fsdax mode, requires nested iomap_begin()/iomap_end() on two files.
Thus, we introduce iomap_iter2() to accept two iteraters to operate
action on two files.

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
---
 fs/iomap/core.c       | 51 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/iomap.h |  2 ++
 2 files changed, 53 insertions(+)

diff --git a/fs/iomap/core.c b/fs/iomap/core.c
index 89a87a1654e8..214538a25110 100644
--- a/fs/iomap/core.c
+++ b/fs/iomap/core.c
@@ -77,3 +77,54 @@ int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
 	iomap_iter_done(iter);
 	return 1;
 }
+
+/**
+ * iomap_iter2 - iterate over a ranges in two files
+ * @iter1:  the first iteration structure
+ * @iter2: the second iteration structure
+ * @ops:   iomap ops provided by the file system
+ *
+ * Iterate two files once.
+ */
+int iomap_iter2(struct iomap_iter *iter1, struct iomap_iter *iter2,
+		const struct iomap_ops *ops)
+{
+	int ret;
+
+	if (iter2->iomap.length && ops->iomap_end) {
+		ret = ops->iomap_end(iter2->inode, iter2->pos, iomap_length(iter2),
+				iter2->processed > 0 ? iter2->processed : 0,
+				iter2->flags, &iter2->iomap);
+		if (ret < 0 && !iter2->processed)
+			return ret;
+	}
+
+	if (iter1->iomap.length && ops->iomap_end) {
+		ret = ops->iomap_end(iter1->inode, iter1->pos, iomap_length(iter1),
+				iter1->processed > 0 ? iter1->processed : 0,
+				iter1->flags, &iter1->iomap);
+		if (ret < 0 && !iter1->processed)
+			return ret;
+	}
+
+	trace_iomap_iter(iter1, ops, _RET_IP_);
+	ret = iomap_iter_advance(iter1);
+	if (ret <= 0)
+		return ret;
+	ret = iomap_iter_advance(iter2);
+	if (ret <= 0)
+		return ret;
+
+	ret = ops->iomap_begin(iter1->inode, iter1->pos, iter1->len, iter1->flags,
+			       &iter1->iomap, &iter1->srcmap);
+	if (ret < 0)
+		return ret;
+	iomap_iter_done(iter1);
+
+	ret = ops->iomap_begin(iter2->inode, iter2->pos, iter2->len, iter2->flags,
+			       &iter2->iomap, &iter2->srcmap);
+	if (ret < 0)
+		return ret;
+	iomap_iter_done(iter2);
+	return 1;
+}
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 24f8489583ca..ebef060c65cd 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -186,6 +186,8 @@ struct iomap_iter {
 };
 
 int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops);
+int iomap_iter2(struct iomap_iter *iter, struct iomap_iter *iter2,
+		const struct iomap_ops *ops);
 
 /**
  * iomap_length - length of the current iomap iteration
-- 
2.32.0