block: loop: introduce lo_discard() and lo_req_flush()

No behaviour change, just move the handling for REQ_DISCARD
and REQ_FLUSH in these two functions.
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

drivers/block/loop.c

@@ -417,54 +417,61 @@ lo_receive(struct loop_device *lo, struct request *rq, int bsize, loff_t pos)
 	return 0;
 }
 
-static int do_req_filebacked(struct loop_device *lo, struct request *rq)
+static int lo_discard(struct loop_device *lo, struct request *rq, loff_t pos)
 {
-	loff_t pos;
-	int ret;
-
-	pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
-
-	if (rq->cmd_flags & REQ_WRITE) {
-		struct file *file = lo->lo_backing_file;
-
-		if (rq->cmd_flags & REQ_FLUSH) {
-			ret = vfs_fsync(file, 0);
-			if (unlikely(ret && ret != -EINVAL)) {
-				ret = -EIO;
-				goto out;
-			}
-		}
-
 	/*
 	 * We use punch hole to reclaim the free space used by the
 	 * image a.k.a. discard. However we do not support discard if
 	 * encryption is enabled, because it may give an attacker
 	 * useful information.
 	 */
-		if (rq->cmd_flags & REQ_DISCARD) {
 	struct file *file = lo->lo_backing_file;
 	int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
+	int ret;
 
-			if ((!file->f_op->fallocate) ||
-			    lo->lo_encrypt_key_size) {
+	if ((!file->f_op->fallocate) || lo->lo_encrypt_key_size) {
 		ret = -EOPNOTSUPP;
 		goto out;
 	}
-			ret = file->f_op->fallocate(file, mode, pos,
-						    blk_rq_bytes(rq));
-			if (unlikely(ret && ret != -EINVAL &&
-				     ret != -EOPNOTSUPP))
+
+	ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
+	if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
 		ret = -EIO;
+ out:
+	return ret;
+}
+
+static int lo_req_flush(struct loop_device *lo, struct request *rq)
+{
+	struct file *file = lo->lo_backing_file;
+	int ret = vfs_fsync(file, 0);
+	if (unlikely(ret && ret != -EINVAL))
+		ret = -EIO;
+
+	return ret;
+}
+
+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 (rq->cmd_flags & REQ_WRITE) {
+
+		if (rq->cmd_flags & REQ_FLUSH)
+			ret = lo_req_flush(lo, rq);
+
+		if (rq->cmd_flags & REQ_DISCARD) {
+			ret = lo_discard(lo, rq, pos);
 			goto out;
 		}
 
 		ret = lo_send(lo, rq, pos);
 
-		if ((rq->cmd_flags & REQ_FUA) && !ret) {
-			ret = vfs_fsync(file, 0);
-			if (unlikely(ret && ret != -EINVAL))
-				ret = -EIO;
-		}
+		if ((rq->cmd_flags & REQ_FUA) && !ret)
+			ret = lo_req_flush(lo, rq);
 	} else
 		ret = lo_receive(lo, rq, lo->lo_blocksize, pos);