From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 C653219922D; Mon, 30 Sep 2024 20:15:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727727343; cv=none; b=Iz1+YKrqd6ql+c3FV0Dzagnt8vVEij0aqaSj2qV8RTB0rAPSR/1y8dZhdg1StGC1BoEy/vRZmR83K/gCT1FlBL96etrGV4s/llbAtbbLPZNXTE3WxHcyFE2iT2xmKhl8y+tRnEiPm9L9f2HvBJYblkwQLR6KUGdQya53IC5UkC8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727727343; c=relaxed/simple; bh=M7S+gdWXGa3PLSbsG6OdZUVcDn/PBbUxrZ5/qJ+DMEw=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=NY7iQAHq98kFPkhqlwUTFbNAHTVf72f4NUece3+jNdthpW3U6KFLTX4pKK3hV+95KTupqV0lXkncBgLvqCYd9GeqPto996Ix/SXQ5RkgWgxKI3+1vojuOZhznbF94J3+PowL3ONyfLJEqfu8wOIWxB+dNctYc/4QJoLBFThqo6E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=MhW83lyu; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=zclkxnGp; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="MhW83lyu"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="zclkxnGp" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1727727339; 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=M7S+gdWXGa3PLSbsG6OdZUVcDn/PBbUxrZ5/qJ+DMEw=; b=MhW83lyupKjcTRSYb6BhSWLgQ/nBViA9+6PePLs6Nipl86pAHMy0p2nNURvKDdJKSPRXRM LNK9srxo+rdQAL/q9aBHffjqipLUd9iXVfrEM2nGga6xk1EKNmG6d2Ta1ITkfukUGHRbr4 FzOtufN+1jlLEL1MJQuEPd9z2bMQhxzlX8wJBlOl+Z3Dv2r3lPF6SWRZTti7ZEZjF6F8fp TEMOlkLQBmBNStXDlGNw812QgoaUuraqXPR8NaAEFkv4wt3hzPtLM5oV4gql/IgfLg5LWl 4KS1klvVzBw662UCQ3TiL7K6fwd9rBTE5tn3xajscpCmUc4eM1Wk68CYAA+Ddg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1727727339; 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=M7S+gdWXGa3PLSbsG6OdZUVcDn/PBbUxrZ5/qJ+DMEw=; b=zclkxnGp1atI4LKz/391HDmc/xuV+6cnt/bWku76i0l7uDYj3Gzik7Lmq5q0tWoZKY4jE1 duHSRiKZaAD49xDg== To: Jeff Layton , John Stultz , Stephen Boyd , Alexander Viro , Christian Brauner , Jan Kara , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Chandan Babu R , "Darrick J. Wong" , Theodore Ts'o , Andreas Dilger , Chris Mason , Josef Bacik , David Sterba , Hugh Dickins , Andrew Morton , Chuck Lever , Vadim Fedorenko Cc: Randy Dunlap , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v8 01/11] timekeeping: move multigrain timestamp floor handling into timekeeper In-Reply-To: <753938ef8e46e9f3d9ea7d977537cd8f5a6533b2.camel@kernel.org> References: <20240914-mgtime-v8-0-5bd872330bed@kernel.org> <20240914-mgtime-v8-1-5bd872330bed@kernel.org> <87bk050xb9.ffs@tglx> <753938ef8e46e9f3d9ea7d977537cd8f5a6533b2.camel@kernel.org> Date: Mon, 30 Sep 2024 22:15:39 +0200 Message-ID: <871q102904.ffs@tglx> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Mon, Sep 30 2024 at 15:27, Jeff Layton wrote: > On Mon, 2024-09-30 at 21:13 +0200, Thomas Gleixner wrote: >> So if that's the intended behaviour then the changelog is misleading at >> best. > > That is the intended behavior and I'll plan to fix the changelog to > clarify this point: > > If someone jumps the realtime clock backward by a large value, then the > realtime timestamp _can_ appear to go backward. This is a problem today > even without this patchset. Correct. > If two files get stamped and a realtime clock jump backward happens in > between them, all bets are off as to which one will appear to have been > modified first. I don't think that is something we can reasonably > prevent, since we must stamp files according to the realtime clock. True. I just was utterly confused about the changelog. > The main thing I'm trying to prevent is the timestamps being misordered > in the absence of such a clock jump. Without tracking the floor as I am > here, that's a possibility. Correct.