fuse: revalidate: don't invalidate if interrupted

If the LOOKUP request triggered from fuse_dentry_revalidate() is
interrupted, then the dentry will be invalidated, possibly resulting in
submounts being unmounted.
Reported-by: Xu Rongbo <xurongbo@baidu.com>
Closes: https://lore.kernel.org/all/CAJfpegswN_CJJ6C3RZiaK6rpFmNyWmXfaEpnQUJ42KCwNF5tWw@mail.gmail.com/
Fixes: 9e6268db ("[PATCH] FUSE - read-write operations")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/dir.c

@@ -258,7 +258,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 			spin_unlock(&fi->lock);
 		}
 		kfree(forget);
-		if (ret == -ENOMEM)
+		if (ret == -ENOMEM || ret == -EINTR)
 			goto out;
 		if (ret || fuse_invalid_attr(&outarg.attr) ||
 		    fuse_stale_inode(inode, outarg.generation, &outarg.attr))