loop: make do_req_filebacked more robust

Use a switch statement to iterate over the possible operations and
error out if it's an incorrect one.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 91c2c881cb49807cf67516ff31aa60f066cb2cbe..c9f2107f7095148dc5e4027d7cb8fdc4794aad01 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -510,14 +510,10 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
        return 0;
 }
 
-
-static inline int lo_rw_simple(struct loop_device *lo,
-               struct request *rq, loff_t pos, bool rw)
+static int do_req_filebacked(struct loop_device *lo, struct request *rq)
 {
        struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
-
-       if (cmd->use_aio)
-               return lo_rw_aio(lo, cmd, pos, rw);
+       loff_t pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
 
        /*
         * lo_write_simple and lo_read_simple should have been covered
@@ -528,37 +524,30 @@ static inline int lo_rw_simple(struct loop_device *lo,
         * of the req at one time. And direct read IO doesn't need to
         * run flush_dcache_page().
         */
-       if (rw == WRITE)
-               return lo_write_simple(lo, rq, pos);
-       else
-               return lo_read_simple(lo, rq, pos);
-}
-
-static int do_req_filebacked(struct loop_device *lo, struct request *rq)
-{
-       loff_t pos;
-       int ret;
-
-       pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
-
-       if (op_is_write(req_op(rq))) {
-               if (req_op(rq) == REQ_OP_FLUSH)
-                       ret = lo_req_flush(lo, rq);
-               else if (req_op(rq) == REQ_OP_DISCARD)
-                       ret = lo_discard(lo, rq, pos);
-               else if (lo->transfer)
-                       ret = lo_write_transfer(lo, rq, pos);
+       switch (req_op(rq)) {
+       case REQ_OP_FLUSH:
+               return lo_req_flush(lo, rq);
+       case REQ_OP_DISCARD:
+               return lo_discard(lo, rq, pos);
+       case REQ_OP_WRITE:
+               if (lo->transfer)
+                       return lo_write_transfer(lo, rq, pos);
+               else if (cmd->use_aio)
+                       return lo_rw_aio(lo, cmd, pos, WRITE);
                else
-                       ret = lo_rw_simple(lo, rq, pos, WRITE);
-
-       } else {
+                       return lo_write_simple(lo, rq, pos);
+       case REQ_OP_READ:
                if (lo->transfer)
-                       ret = lo_read_transfer(lo, rq, pos);
+                       return lo_read_transfer(lo, rq, pos);
+               else if (cmd->use_aio)
+                       return lo_rw_aio(lo, cmd, pos, READ);
                else
-                       ret = lo_rw_simple(lo, rq, pos, READ);
+                       return lo_read_simple(lo, rq, pos);
+       default:
+               WARN_ON_ONCE(1);
+               return -EIO;
+               break;
        }
-
-       return ret;
 }
 
 struct switch_request {