From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9D9412066C0 for ; Fri, 10 Jan 2025 07:34:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736494467; cv=none; b=Z6bEBNqYOyET++3FY98vMCL/3ihWs0J5mb5u4reEXrRUcSTW/sF3DG1a0pFd2seDfx0QN9zaEy8tX69rON1YQO5QkiFmOJuDg6CJvCqv/tqKO70QRYfzFkcZjptRntH7SlRm4kQxsmlDfhrc78iwPHRcRPkzXlMLsIVjN3nx3Ms= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736494467; c=relaxed/simple; bh=sTJ+hZN2LcR24cVozieVOxjojgy6K2eGueL0rS8Bu1s=; h=From:In-Reply-To:References:To:Cc:Subject:MIME-Version: Content-Type:Date:Message-ID; b=IDlSf4MlADWLNuV3Ca1Jl4zC5c67fgsTWwtmfrTSPFE2xaZAFrV+qvpUCB2NoCgVPyEgNGao3XhLPTAY+wtyvPcm9YuOTl4fQZygWrq5dTDABOL4cH+d9J721+4q3J8oGCUN0DkC0hLKTVctAAr9iVFd6tp0rN65SA/ElHSWUm8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=E243vpjz; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="E243vpjz" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1736494464; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=W9HOM+mW+PNbdvdR9YUqOCML6H4X28NFg2Df5cgsARQ=; b=E243vpjzhWf5Qgf3ulxkUEQdXDCEr06apOy4/2OakErwWzdCA1w/NQwoQ4HhlWQ1gOEbDy wTx/iL/SzV5YFOW/a3lQq7h4brPDdo3pRy3MNcW0URCL0zfc/zf3M3uFA49KrkNhGYrG+D Le24MQU4fMAfSV6UpKcWiq0WHb/bINU= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-636-WEchz7qiOY65-SCNEzlT7A-1; Fri, 10 Jan 2025 02:34:19 -0500 X-MC-Unique: WEchz7qiOY65-SCNEzlT7A-1 X-Mimecast-MFC-AGG-ID: WEchz7qiOY65-SCNEzlT7A Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3134D195606B; Fri, 10 Jan 2025 07:34:17 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.12]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 440E81955BE3; Fri, 10 Jan 2025 07:34:12 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20250110024303.4157645-4-viro@zeniv.linux.org.uk> References: <20250110024303.4157645-4-viro@zeniv.linux.org.uk> <20250110023854.GS1977892@ZenIV> <20250110024303.4157645-1-viro@zeniv.linux.org.uk> To: Al Viro Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org, agruenba@redhat.com, amir73il@gmail.com, brauner@kernel.org, ceph-devel@vger.kernel.org, hubcap@omnibond.com, jack@suse.cz, krisman@kernel.org, linux-nfs@vger.kernel.org, miklos@szeredi.hu, torvalds@linux-foundation.org Subject: Re: [PATCH 04/20] dissolve external_name.u into separate members Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1479432.1736494451.1@warthog.procyon.org.uk> Date: Fri, 10 Jan 2025 07:34:11 +0000 Message-ID: <1479433.1736494451@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Al Viro wrote: > struct external_name { > - struct { > - atomic_t count; // ->count and ->head can't be combined > - struct rcu_head head; // see take_dentry_name_snapshot() > - } u; > + atomic_t count; // ->count and ->head can't be combined > + struct rcu_head head; // see take_dentry_name_snapshot() > unsigned char name[]; > }; This gets you a 4-byte hole between count and head on a 64-bit system. Did you want to flip the order of count and head? David