[PATCH V4 1/6] loop: add helper lo_cmd_nr_bvec()

[Ming Lei <ming.lei@redhat.com>]

Add lo_cmd_nr_bvec() and prepare for refactoring lo_rw_aio().

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/block/loop.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 053a086d547e..af443651dff5 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -337,6 +337,19 @@ static void lo_rw_aio_complete(struct kiocb *iocb, long ret)
 	lo_rw_aio_do_completion(cmd);
 }
 
+static inline unsigned lo_cmd_nr_bvec(struct loop_cmd *cmd)
+{
+	struct request *rq = blk_mq_rq_from_pdu(cmd);
+	struct req_iterator rq_iter;
+	struct bio_vec tmp;
+	int nr_bvec = 0;
+
+	rq_for_each_bvec(tmp, rq, rq_iter)
+		nr_bvec++;
+
+	return nr_bvec;
+}
+
 static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 		     loff_t pos, int rw)
 {
@@ -348,12 +361,9 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 	struct file *file = lo->lo_backing_file;
 	struct bio_vec tmp;
 	unsigned int offset;
-	int nr_bvec = 0;
+	int nr_bvec = lo_cmd_nr_bvec(cmd);
 	int ret;
 
-	rq_for_each_bvec(tmp, rq, rq_iter)
-		nr_bvec++;
-
 	if (rq->bio != rq->biotail) {
 
 		bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
-- 
2.47.0