fuse: honor AT_STATX_DONT_SYNC

The description of this flag says "Don't sync attributes with the server".
In other words: always use the attributes cached in the kernel and don't
send network or local messages to refresh the attributes.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/dir.c

@@ -924,12 +924,13 @@ static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
 }
 
 static int fuse_update_get_attr(struct inode *inode, struct file *file,
-				struct kstat *stat)
+				struct kstat *stat, unsigned int flags)
 {
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	int err = 0;
 
-	if (time_before64(fi->i_time, get_jiffies_64())) {
+	if (!(flags & AT_STATX_DONT_SYNC) &&
+	    time_before64(fi->i_time, get_jiffies_64())) {
 		forget_all_cached_acls(inode);
 		err = fuse_do_getattr(inode, stat, file);
 	} else if (stat) {
@@ -943,7 +944,7 @@ static int fuse_update_get_attr(struct inode *inode, struct file *file,
 
 int fuse_update_attributes(struct inode *inode, struct file *file)
 {
-	return fuse_update_get_attr(inode, file, NULL);
+	return fuse_update_get_attr(inode, file, NULL, 0);
 }
 
 int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,
@@ -1794,7 +1795,7 @@ static int fuse_getattr(const struct path *path, struct kstat *stat,
 	if (!fuse_allow_current_process(fc))
 		return -EACCES;
 
-	return fuse_update_get_attr(inode, NULL, stat);
+	return fuse_update_get_attr(inode, NULL, stat, flags);
 }
 
 static const struct inode_operations fuse_dir_inode_operations = {