iomap: switch iomap_bmap to use iomap_iter

Rewrite the ->bmap implementation based on iomap_iter.
Signed-off-by: Christoph Hellwig <hch@lst.de>
[djwong: restructure the loop to make its behavior a little clearer]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/iomap/fiemap.c

@@ -92,37 +92,32 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
 }
 EXPORT_SYMBOL_GPL(iomap_fiemap);
 
-static loff_t
-iomap_bmap_actor(struct inode *inode, loff_t pos, loff_t length,
-		void *data, struct iomap *iomap, struct iomap *srcmap)
-{
-	sector_t *bno = data, addr;
-
-	if (iomap->type == IOMAP_MAPPED) {
-		addr = (pos - iomap->offset + iomap->addr) >> inode->i_blkbits;
-		*bno = addr;
-	}
-	return 0;
-}
-
 /* legacy ->bmap interface.  0 is the error return (!) */
 sector_t
 iomap_bmap(struct address_space *mapping, sector_t bno,
 		const struct iomap_ops *ops)
 {
-	struct inode *inode = mapping->host;
-	loff_t pos = bno << inode->i_blkbits;
-	unsigned blocksize = i_blocksize(inode);
+	struct iomap_iter iter = {
+		.inode	= mapping->host,
+		.pos	= (loff_t)bno << mapping->host->i_blkbits,
+		.len	= i_blocksize(mapping->host),
+		.flags	= IOMAP_REPORT,
+	};
+	const unsigned int blkshift = mapping->host->i_blkbits - SECTOR_SHIFT;
 	int ret;
 
 	if (filemap_write_and_wait(mapping))
 		return 0;
 
 	bno = 0;
-	ret = iomap_apply(inode, pos, blocksize, 0, ops, &bno,
-			  iomap_bmap_actor);
+	while ((ret = iomap_iter(&iter, ops)) > 0) {
+		if (iter.iomap.type == IOMAP_MAPPED)
+			bno = iomap_sector(&iter.iomap, iter.pos) >> blkshift;
+		/* leave iter.processed unset to abort loop */
+	}
 	if (ret)
 		return 0;
+
 	return bno;
 }
 EXPORT_SYMBOL_GPL(iomap_bmap);