[PATCH 1/3] loop: cleanup lo_rw_aio

[Christoph Hellwig]

Port over the changes from the zloop driver to remove the need for
the local bio, bvec and offset variables and clean up the code by
that.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/block/loop.c | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 0000913f7efc..310de0463beb 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -342,23 +342,19 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 {
 	struct iov_iter iter;
 	struct req_iterator rq_iter;
-	struct bio_vec *bvec;
 	struct request *rq = blk_mq_rq_from_pdu(cmd);
-	struct bio *bio = rq->bio;
 	struct file *file = lo->lo_backing_file;
-	struct bio_vec tmp;
-	unsigned int offset;
 	unsigned int nr_bvec;
 	int ret;
 
 	nr_bvec = blk_rq_nr_bvec(rq);
 
 	if (rq->bio != rq->biotail) {
+		struct bio_vec tmp, *bvec;
 
-		bvec = kmalloc_objs(struct bio_vec, nr_bvec, GFP_NOIO);
-		if (!bvec)
+		cmd->bvec = kmalloc_objs(*cmd->bvec, nr_bvec, GFP_NOIO);
+		if (!cmd->bvec)
 			return -EIO;
-		cmd->bvec = bvec;
 
 		/*
 		 * The bios of the request may be started from the middle of
@@ -366,26 +362,26 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 		 * copy bio->bi_iov_vec to new bvec. The rq_for_each_bvec
 		 * API will take care of all details for us.
 		 */
+		bvec = cmd->bvec;
 		rq_for_each_bvec(tmp, rq, rq_iter) {
 			*bvec = tmp;
 			bvec++;
 		}
-		bvec = cmd->bvec;
-		offset = 0;
+		iov_iter_bvec(&iter, rw, cmd->bvec, nr_bvec, blk_rq_bytes(rq));
+		iter.iov_offset = 0;
 	} else {
 		/*
 		 * Same here, this bio may be started from the middle of the
 		 * 'bvec' because of bio splitting, so offset from the bvec
 		 * must be passed to iov iterator
 		 */
-		offset = bio->bi_iter.bi_bvec_done;
-		bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
+		iov_iter_bvec(&iter, rw,
+			__bvec_iter_bvec(rq->bio->bi_io_vec, rq->bio->bi_iter),
+			nr_bvec, blk_rq_bytes(rq));
+		iter.iov_offset = rq->bio->bi_iter.bi_bvec_done;
 	}
 	atomic_set(&cmd->ref, 2);
 
-	iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
-	iter.iov_offset = offset;
-
 	cmd->iocb.ki_pos = pos;
 	cmd->iocb.ki_filp = file;
 	cmd->iocb.ki_ioprio = req_get_ioprio(rq);
-- 
2.53.0