ext4: code cleanup for get_next_id

Now the checks in ext4_get_next_id() and dquot_get_next_id()
are almost the same, so just call dquot_get_next_id() instead
of ext4_get_next_id().
Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Link: https://lore.kernel.org/r/20191006103028.31299-1-cgxu519@mykernel.netSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -1374,7 +1374,6 @@ static ssize_t ext4_quota_write(struct super_block *sb, int type,
 static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
 			     unsigned int flags);
 static int ext4_enable_quotas(struct super_block *sb);
-static int ext4_get_next_id(struct super_block *sb, struct kqid *qid);
 
 static struct dquot **ext4_get_dquots(struct inode *inode)
 {
@@ -1392,7 +1391,7 @@ static const struct dquot_operations ext4_quota_operations = {
 	.destroy_dquot		= dquot_destroy,
 	.get_projid		= ext4_get_projid,
 	.get_inode_usage	= ext4_get_inode_usage,
-	.get_next_id		= ext4_get_next_id,
+	.get_next_id		= dquot_get_next_id,
 };
 
 static const struct quotactl_ops ext4_qctl_operations = {
@@ -6002,18 +6001,6 @@ static ssize_t ext4_quota_write(struct super_block *sb, int type,
 	}
 	return len;
 }
-
-static int ext4_get_next_id(struct super_block *sb, struct kqid *qid)
-{
-	const struct quota_format_ops	*ops;
-
-	if (!sb_has_quota_loaded(sb, qid->type))
-		return -ESRCH;
-	ops = sb_dqopt(sb)->ops[qid->type];
-	if (!ops || !ops->get_next_id)
-		return -ENOSYS;
-	return dquot_get_next_id(sb, qid);
-}
 #endif
 
 static struct dentry *ext4_mount(struct file_system_type *fs_type, int flags,