fuse: always flush dirty data on close(2)

to #30030885

commit 614c026e8a46636198da93ec30719f93975bb26a upstream

We want cached data to synced with the userspace filesystem on close(), for
example to allow getting correct st_blocks value.  Do this regardless of
whether the userspace filesystem implements a FLUSH method or not.
Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: NEryu Guan <eguan@linux.alibaba.com>
Reviewed-by: NLiu Bo <bo.liu@linux.alibaba.com>

fs/fuse/file.c

@@ -410,10 +410,6 @@ static int fuse_flush(struct file *file, fl_owner_t id)
 	if (is_bad_inode(inode))
 		return -EIO;
 
-	err = 0;
-	if (fc->no_flush)
-		goto inval_attr_out;
-
 	err = write_inode_now(inode, 1);
 	if (err)
 		return err;
@@ -426,6 +422,10 @@ static int fuse_flush(struct file *file, fl_owner_t id)
 	if (err)
 		return err;
 
+	err = 0;
+	if (fc->no_flush)
+		goto inval_attr_out;
+
 	req = fuse_get_req_nofail_nopages(fc, file);
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.fh = ff->fh;