loop: add helper lo_cmd_nr_bvec()

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

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 13ce229d450cd308ab96b98f7fc8fd49efe24df9..c6c37c9df193d09b085ecf051eac19a99ac6eff1 100644 (file)
--- 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),