iomap: add a iomap_sector helper

Factor the repeated calculation of the on-disk sector for a given logical
block into a littler helper.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/iomap.c

@@ -96,6 +96,12 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
 	return written ? written : ret;
 }
 
+static sector_t
+iomap_sector(struct iomap *iomap, loff_t pos)
+{
+	return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT;
+}
+
 static void
 iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
 {
@@ -353,11 +359,8 @@ static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
 static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
 		struct iomap *iomap)
 {
-	sector_t sector = (iomap->addr +
-			   (pos & PAGE_MASK) - iomap->offset) >> 9;
-
-	return __dax_zero_page_range(iomap->bdev, iomap->dax_dev, sector,
-			offset, bytes);
+	return __dax_zero_page_range(iomap->bdev, iomap->dax_dev,
+			iomap_sector(iomap, pos & PAGE_MASK), offset, bytes);
 }
 
 static loff_t
@@ -839,8 +842,7 @@ iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
 
 	bio = bio_alloc(GFP_KERNEL, 1);
 	bio_set_dev(bio, iomap->bdev);
-	bio->bi_iter.bi_sector =
-		(iomap->addr + pos - iomap->offset) >> 9;
+	bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
 	bio->bi_private = dio;
 	bio->bi_end_io = iomap_dio_bio_end_io;
 
@@ -934,8 +936,7 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
 
 		bio = bio_alloc(GFP_KERNEL, nr_pages);
 		bio_set_dev(bio, iomap->bdev);
-		bio->bi_iter.bi_sector =
-			(iomap->addr + pos - iomap->offset) >> 9;
+		bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
 		bio->bi_write_hint = dio->iocb->ki_hint;
 		bio->bi_private = dio;
 		bio->bi_end_io = iomap_dio_bio_end_io;