iomap: constify iomap_iter_srcmap

The srcmap returned from iomap_iter_srcmap is never modified, so mark
the iomap returned from it const and constify a lot of code that never
modifies the iomap.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/iomap/buffered-io.c

@@ -205,10 +205,10 @@ struct iomap_readpage_ctx {
 	struct readahead_control *rac;
 };
 
-static loff_t iomap_read_inline_data(struct iomap_iter *iter,
+static loff_t iomap_read_inline_data(const struct iomap_iter *iter,
 		struct page *page)
 {
-	struct iomap *iomap = iomap_iter_srcmap(iter);
+	const struct iomap *iomap = iomap_iter_srcmap(iter);
 	size_t size = i_size_read(iter->inode) - iomap->offset;
 	size_t poff = offset_in_page(iomap->offset);
 	void *addr;
@@ -234,20 +234,20 @@ static loff_t iomap_read_inline_data(struct iomap_iter *iter,
 	return PAGE_SIZE - poff;
 }
 
-static inline bool iomap_block_needs_zeroing(struct iomap_iter *iter,
+static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
 		loff_t pos)
 {
-	struct iomap *srcmap = iomap_iter_srcmap(iter);
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 
 	return srcmap->type != IOMAP_MAPPED ||
 		(srcmap->flags & IOMAP_F_NEW) ||
 		pos >= i_size_read(iter->inode);
 }
 
-static loff_t iomap_readpage_iter(struct iomap_iter *iter,
+static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx, loff_t offset)
 {
-	struct iomap *iomap = &iter->iomap;
+	const struct iomap *iomap = &iter->iomap;
 	loff_t pos = iter->pos + offset;
 	loff_t length = iomap_length(iter) - offset;
 	struct page *page = ctx->cur_page;
@@ -352,7 +352,7 @@ iomap_readpage(struct page *page, const struct iomap_ops *ops)
 }
 EXPORT_SYMBOL_GPL(iomap_readpage);
 
-static loff_t iomap_readahead_iter(struct iomap_iter *iter,
+static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx)
 {
 	loff_t length = iomap_length(iter);
@@ -536,10 +536,10 @@ iomap_read_page_sync(loff_t block_start, struct page *page, unsigned poff,
 	return submit_bio_wait(&bio);
 }
 
-static int __iomap_write_begin(struct iomap_iter *iter, loff_t pos,
+static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 		unsigned len, struct page *page)
 {
-	struct iomap *srcmap = iomap_iter_srcmap(iter);
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	struct iomap_page *iop = iomap_page_create(iter->inode, page);
 	loff_t block_size = i_blocksize(iter->inode);
 	loff_t block_start = round_down(pos, block_size);
@@ -577,7 +577,7 @@ static int __iomap_write_begin(struct iomap_iter *iter, loff_t pos,
 	return 0;
 }
 
-static int iomap_write_begin_inline(struct iomap_iter *iter,
+static int iomap_write_begin_inline(const struct iomap_iter *iter,
 		struct page *page)
 {
 	int ret;
@@ -591,11 +591,11 @@ static int iomap_write_begin_inline(struct iomap_iter *iter,
 	return 0;
 }
 
-static int iomap_write_begin(struct iomap_iter *iter, loff_t pos, unsigned len,
-		struct page **pagep)
+static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
+		unsigned len, struct page **pagep)
 {
 	const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
-	struct iomap *srcmap = iomap_iter_srcmap(iter);
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	struct page *page;
 	int status = 0;
 
@@ -666,10 +666,10 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 	return copied;
 }
 
-static size_t iomap_write_end_inline(struct iomap_iter *iter, struct page *page,
-		loff_t pos, size_t copied)
+static size_t iomap_write_end_inline(const struct iomap_iter *iter,
+		struct page *page, loff_t pos, size_t copied)
 {
-	struct iomap *iomap = &iter->iomap;
+	const struct iomap *iomap = &iter->iomap;
 	void *addr;
 
 	WARN_ON_ONCE(!PageUptodate(page));
@@ -689,7 +689,7 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
 		size_t copied, struct page *page)
 {
 	const struct iomap_page_ops *page_ops = iter->iomap.page_ops;
-	struct iomap *srcmap = iomap_iter_srcmap(iter);
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	loff_t old_size = iter->inode->i_size;
 	size_t ret;
 
@@ -814,7 +814,7 @@ EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
 static loff_t iomap_unshare_iter(struct iomap_iter *iter)
 {
 	struct iomap *iomap = &iter->iomap;
-	struct iomap *srcmap = iomap_iter_srcmap(iter);
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	loff_t pos = iter->pos;
 	loff_t length = iomap_length(iter);
 	long status = 0;
@@ -890,7 +890,7 @@ static s64 __iomap_zero_iter(struct iomap_iter *iter, loff_t pos, u64 length)
 static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
 {
 	struct iomap *iomap = &iter->iomap;
-	struct iomap *srcmap = iomap_iter_srcmap(iter);
+	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	loff_t pos = iter->pos;
 	loff_t length = iomap_length(iter);
 	loff_t written = 0;

include/linux/iomap.h

@@ -211,7 +211,7 @@ static inline u64 iomap_length(const struct iomap_iter *iter)
  * for a given operation, which may or may no be identical to the destination
  * map in &i->iomap.
  */
-static inline struct iomap *iomap_iter_srcmap(struct iomap_iter *i)
+static inline const struct iomap *iomap_iter_srcmap(const struct iomap_iter *i)
 {
 	if (i->srcmap.type != IOMAP_HOLE)
 		return &i->srcmap;