nbd: Convert to DEFINE_SHOW_ATTRIBUTE

Use DEFINE_SHOW_ATTRIBUTE macro to simplify the code.
Signed-off-by: NLiao Pingfang <winndows@163.com>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/nbd.c

@@ -1521,17 +1521,7 @@ static int nbd_dbg_tasks_show(struct seq_file *s, void *unused)
 	return 0;
 }
 
-static int nbd_dbg_tasks_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, nbd_dbg_tasks_show, inode->i_private);
-}
-
-static const struct file_operations nbd_dbg_tasks_ops = {
-	.open = nbd_dbg_tasks_open,
-	.read = seq_read,
-	.llseek = seq_lseek,
-	.release = single_release,
-};
+DEFINE_SHOW_ATTRIBUTE(nbd_dbg_tasks);
 
 static int nbd_dbg_flags_show(struct seq_file *s, void *unused)
 {
@@ -1556,17 +1546,7 @@ static int nbd_dbg_flags_show(struct seq_file *s, void *unused)
 	return 0;
 }
 
-static int nbd_dbg_flags_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, nbd_dbg_flags_show, inode->i_private);
-}
-
-static const struct file_operations nbd_dbg_flags_ops = {
-	.open = nbd_dbg_flags_open,
-	.read = seq_read,
-	.llseek = seq_lseek,
-	.release = single_release,
-};
+DEFINE_SHOW_ATTRIBUTE(nbd_dbg_flags);
 
 static int nbd_dev_dbg_init(struct nbd_device *nbd)
 {
@@ -1584,11 +1564,11 @@ static int nbd_dev_dbg_init(struct nbd_device *nbd)
 	}
 	config->dbg_dir = dir;
 
-	debugfs_create_file("tasks", 0444, dir, nbd, &nbd_dbg_tasks_ops);
+	debugfs_create_file("tasks", 0444, dir, nbd, &nbd_dbg_tasks_fops);
 	debugfs_create_u64("size_bytes", 0444, dir, &config->bytesize);
 	debugfs_create_u32("timeout", 0444, dir, &nbd->tag_set.timeout);
 	debugfs_create_u64("blocksize", 0444, dir, &config->blksize);
-	debugfs_create_file("flags", 0444, dir, nbd, &nbd_dbg_flags_ops);
+	debugfs_create_file("flags", 0444, dir, nbd, &nbd_dbg_flags_fops);
 
 	return 0;
 }