From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09221C433EF for ; Thu, 28 Apr 2022 12:51:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235574AbiD1MyP (ORCPT ); Thu, 28 Apr 2022 08:54:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346751AbiD1Mx6 (ORCPT ); Thu, 28 Apr 2022 08:53:58 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC3AE5F8CE for ; Thu, 28 Apr 2022 05:50:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=cwijA81IbdDzVgkp834v9Z0FlR4apqNoRSdhgwYBdho=; b=fjXugTe6rBmA2uyGMAapYVa9Nt 4Wwm2i+tEun1CAOwWl4dbQ+nFNOCCj0Pp4fU8geyDrhzuYWNWOM8vdcXBgz0xZQl/TqLeevsKBzv8 Ao7s27t1tdzMmSRt7XTkDOOg4wbEC0Ki+Z+FD6NxWdo+HstkR3vc6u27krHMubXg2g8CZb2+jh6ze h0RKWlVsIoUmNC8eGHgvopES/3Wd1TuYMNId5NW0KywLhIo3jQaicgPEW5BH0Mrs2l8tj9GMuJAnO HSHvMPgZ7E07FEnW0pJ4iRbkXrM96aV318bNHeYEWLfGmL9q8hPuj6XR+a4L50LH1xmWcSADVVO+D 1wAXFX5w==; Received: from hch by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nk3bW-006tNK-QZ; Thu, 28 Apr 2022 12:50:42 +0000 Date: Thu, 28 Apr 2022 05:50:42 -0700 From: Christoph Hellwig To: "Darrick J. Wong" Cc: david@fromorbit.com, linux-xfs@vger.kernel.org Subject: Re: [PATCH 4/9] xfs: create shadow transaction reservations for computing minimum log size Message-ID: References: <165102071223.3922658.5241787533081256670.stgit@magnolia> <165102073482.3922658.3874181264513799865.stgit@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <165102073482.3922658.3874181264513799865.stgit@magnolia> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, Apr 26, 2022 at 05:52:14PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong > > Every time someone changes the transaction reservation sizes, they > introduce potential compatibility problems if the changes affect the > minimum log size that we validate at mount time. If the minimum log > size gets larger (which should be avoided because doing so presents a > serious risk of log livelock), filesystems created with old mkfs will > not mount on a newer kernel; if the minimum size shrinks, filesystems > created with newer mkfs will not mount on older kernels. > > Therefore, enable the creation of a shadow log reservation structure > where we can "undo" the effects of tweaks when computing minimum log > sizes. These shadow reservations should never be used in practice, but > they insulate us from perturbations in minimum log size. Looks good: Reviewed-by: Christoph Hellwig