fuse: make fuse_dentry_revalidate() RCU aware

Only bail out of fuse_dentry_revalidate() on LOOKUP_RCU when blocking
is actually necessary.

CC: Nick Piggin <npiggin@gmail.com>
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>

fs/fuse/dir.c

@@ -158,10 +158,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
 {
 	struct inode *inode;
 
-	if (nd && nd->flags & LOOKUP_RCU)
-		return -ECHILD;
-
-	inode = entry->d_inode;
+	inode = ACCESS_ONCE(entry->d_inode);
 	if (inode && is_bad_inode(inode))
 		return 0;
 	else if (fuse_dentry_time(entry) < get_jiffies_64()) {
@@ -177,6 +174,9 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
 		if (!inode)
 			return 0;
 
+		if (nd->flags & LOOKUP_RCU)
+			return -ECHILD;
+
 		fc = get_fuse_conn(inode);
 		req = fuse_get_req(fc);
 		if (IS_ERR(req))