iomap: introduce a full map advance helper

Various iomap_iter_advance() calls advance by the full mapping
length and thus have no need for the current length input or
post-advance remaining length output from the standard advance
function. Add an iomap_iter_advance_full() helper to clean up these
cases.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Link: https://lore.kernel.org/r/20250224144757.237706-13-bfoster@redhat.com
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Brian Foster

fs/dax.c

@@ -1266,11 +1266,11 @@ static int dax_unshare_iter(struct iomap_iter *iter)
 	u64 copy_len = iomap_length(iter);
 	u32 mod;
 	int id = 0;
-	s64 ret = iomap_length(iter);
+	s64 ret;
 	void *daddr = NULL, *saddr = NULL;
 
 	if (!iomap_want_unshare_iter(iter))
-		return iomap_iter_advance(iter, &ret);
+		return iomap_iter_advance_full(iter);
 
 	/*
 	 * Extend the file range to be aligned to fsblock/pagesize, because
@@ -1300,16 +1300,14 @@ static int dax_unshare_iter(struct iomap_iter *iter)
 	if (ret < 0)
 		goto out_unlock;
 
-	if (copy_mc_to_kernel(daddr, saddr, copy_len) == 0)
-		ret = iomap_length(iter);
-	else
+	if (copy_mc_to_kernel(daddr, saddr, copy_len) != 0)
 		ret = -EIO;
 
 out_unlock:
 	dax_read_unlock(id);
 	if (ret < 0)
 		return dax_mem2blk_err(ret);
-	return iomap_iter_advance(iter, &ret);
+	return iomap_iter_advance_full(iter);
 }
 
 int dax_file_unshare(struct inode *inode, loff_t pos, loff_t len,

fs/iomap/buffered-io.c

@@ -1433,8 +1433,7 @@ iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
 				range_dirty = false;
 				status = iomap_zero_iter_flush_and_stale(&iter);
 			} else {
-				u64 length = iomap_length(&iter);
-				status = iomap_iter_advance(&iter, &length);
+				status = iomap_iter_advance_full(&iter);
 			}
 			iter.status = status;
 			continue;

fs/iomap/fiemap.c

@@ -42,7 +42,6 @@ static int iomap_to_fiemap(struct fiemap_extent_info *fi,
 static int iomap_fiemap_iter(struct iomap_iter *iter,
 		struct fiemap_extent_info *fi, struct iomap *prev)
 {
-	u64 length = iomap_length(iter);
 	int ret;
 
 	if (iter->iomap.type == IOMAP_HOLE)
@@ -56,7 +55,7 @@ static int iomap_fiemap_iter(struct iomap_iter *iter,
 		return 0;
 
 advance:
-	return iomap_iter_advance(iter, &length);
+	return iomap_iter_advance_full(iter);
 }
 
 int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,

fs/iomap/swapfile.c

@@ -97,8 +97,6 @@ static int iomap_swapfile_fail(struct iomap_swapfile_info *isi, const char *str)
 static int iomap_swapfile_iter(struct iomap_iter *iter,
 		struct iomap *iomap, struct iomap_swapfile_info *isi)
 {
-	u64 length = iomap_length(iter);
-
 	switch (iomap->type) {
 	case IOMAP_MAPPED:
 	case IOMAP_UNWRITTEN:
@@ -135,7 +133,7 @@ static int iomap_swapfile_iter(struct iomap_iter *iter,
 		memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 	}
 
-	return iomap_iter_advance(iter, &length);
+	return iomap_iter_advance_full(iter);
 }
 
 /*

include/linux/iomap.h

@@ -271,6 +271,16 @@ static inline u64 iomap_length(const struct iomap_iter *iter)
 	return iomap_length_trim(iter, iter->pos, iter->len);
 }
 
+/**
+ * iomap_iter_advance_full - advance by the full length of current map
+ */
+static inline int iomap_iter_advance_full(struct iomap_iter *iter)
+{
+	u64 length = iomap_length(iter);
+
+	return iomap_iter_advance(iter, &length);
+}
+
 /**
  * iomap_iter_srcmap - return the source map for the current iomap iteration
  * @i: iteration structure