block: factor out a chunk_size_left helper

Factor out a helper from blk_max_size_offset so that it can be reused
independently.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
Link: https://lore.kernel.org/r/20220614090934.570632-2-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/blkdev.h

@@ -934,6 +934,17 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
 	return q->limits.max_sectors;
 }
 
+/*
+ * Return how much of the chunk is left to be used for I/O at a given offset.
+ */
+static inline unsigned int blk_chunk_sectors_left(sector_t offset,
+		unsigned int chunk_sectors)
+{
+	if (unlikely(!is_power_of_2(chunk_sectors)))
+		return chunk_sectors - sector_div(offset, chunk_sectors);
+	return chunk_sectors - (offset & (chunk_sectors - 1));
+}
+
 /*
  * Return maximum size of a request at given offset. Only valid for
  * file system requests.
@@ -949,12 +960,8 @@ static inline unsigned int blk_max_size_offset(struct request_queue *q,
 			return q->limits.max_sectors;
 	}
 
-	if (likely(is_power_of_2(chunk_sectors)))
-		chunk_sectors -= offset & (chunk_sectors - 1);
-	else
-		chunk_sectors -= sector_div(offset, chunk_sectors);
-
-	return min(q->limits.max_sectors, chunk_sectors);
+	return min(q->limits.max_sectors,
+			blk_chunk_sectors_left(offset, chunk_sectors));
 }
 
 /*