[PATCH V2 1/5] loop: simplify do_req_filebacked()

[Ming Lei]

lo_rw_aio() is only called for READ/WRITE operation, which can be
figured out from request directly, so remove 'rw' parameter from
lo_rw_aio(), meantime rename the local variable as 'dir' which makes
the check more readable in lo_rw_aio().

Meantime add lo_rw_simple() so that do_req_filebacked() can be
simplified in the following way:

```
        if (cmd->use_aio)
                return lo_rw_aio(lo, cmd, pos);
        else
                return lo_rw_simple(lo, rq, pos);
```

Signed-off-by: Ming Lei <ming....@redhat.com>
---
 drivers/block/loop.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 657bf53decf3..554f6cefe8f6 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -285,6 +285,13 @@ static int lo_read_simple(struct loop_device *lo, struct 
request *rq,
        return 0;
 }
 
+static int lo_rw_simple(struct loop_device *lo, struct request *rq, loff_t pos)
+{
+       if (req_op(rq) == REQ_OP_READ)
+               return lo_read_simple(lo, rq, pos);
+       return lo_write_simple(lo, rq, pos);
+}
+
 static void loop_clear_limits(struct loop_device *lo, int mode)
 {
        struct queue_limits lim = queue_limits_start_update(lo->lo_queue);
@@ -400,13 +407,13 @@ static void lo_rw_aio_complete(struct kiocb *iocb, long 
ret)
        lo_rw_aio_do_completion(cmd);
 }
 
-static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
-                    loff_t pos, int rw)
+static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, loff_t pos)
 {
        struct iov_iter iter;
        struct req_iterator rq_iter;
        struct bio_vec *bvec;
        struct request *rq = blk_mq_rq_from_pdu(cmd);
+       int dir = (req_op(rq) == REQ_OP_READ) ? ITER_DEST : ITER_SOURCE;
        struct bio *bio = rq->bio;
        struct file *file = lo->lo_backing_file;
        struct bio_vec tmp;
@@ -448,7 +455,7 @@ static int lo_rw_aio(struct loop_device *lo, struct 
loop_cmd *cmd,
        }
        atomic_set(&cmd->ref, 2);
 
-       iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
+       iov_iter_bvec(&iter, dir, bvec, nr_bvec, blk_rq_bytes(rq));
        iter.iov_offset = offset;
 
        cmd->iocb.ki_pos = pos;
@@ -457,7 +464,7 @@ static int lo_rw_aio(struct loop_device *lo, struct 
loop_cmd *cmd,
        cmd->iocb.ki_flags = IOCB_DIRECT;
        cmd->iocb.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
 
-       if (rw == ITER_SOURCE)
+       if (dir == ITER_SOURCE)
                ret = file->f_op->write_iter(&cmd->iocb, &iter);
        else
                ret = file->f_op->read_iter(&cmd->iocb, &iter);
@@ -498,15 +505,11 @@ static int do_req_filebacked(struct loop_device *lo, 
struct request *rq)
        case REQ_OP_DISCARD:
                return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE);
        case REQ_OP_WRITE:
-               if (cmd->use_aio)
-                       return lo_rw_aio(lo, cmd, pos, ITER_SOURCE);
-               else
-                       return lo_write_simple(lo, rq, pos);
        case REQ_OP_READ:
                if (cmd->use_aio)
-                       return lo_rw_aio(lo, cmd, pos, ITER_DEST);
+                       return lo_rw_aio(lo, cmd, pos);
                else
-                       return lo_read_simple(lo, rq, pos);
+                       return lo_rw_simple(lo, rq, pos);
        default:
                WARN_ON_ONCE(1);
                return -EIO;
-- 
2.47.0