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 500BCCCA473 for ; Thu, 9 Jun 2022 12:36:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245198AbiFIMgP (ORCPT ); Thu, 9 Jun 2022 08:36:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245479AbiFIMgN (ORCPT ); Thu, 9 Jun 2022 08:36:13 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A87FA22BDE for ; Thu, 9 Jun 2022 05:36:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=wBSgtsx5slcSTW2KsjMgLEFNd7Ur2Tu3G3a/elprB+U=; b=ZI+i8P6h+5IBzj6AR2Gc94T7gB QbCeXQmUvSXmP1JFGAA1voPT3vgoXzcnoOrGxLJjD9sa4c/Zp8Uq1658vxan/xVPgrPY2cX2AxK/v riu7QjdZsHLuvyaMm5rKvMF7TxJA+MEKiLFGi9uwfUJyIsA4+qPfPzdkIIRyF8FMr8a+Alkzx9Jfj iW9huYT22m8PsJ/fOEpAIoG+5BLcR3PB5hsN1P/Bus3JcM1EOg0T030VQ1zkp9AQTXA9iKRmZIQ+S nqX49z1MPk57Vxy3WXLMvGjX8zChnHW93Scqj6waZdP62AdmqckghGCgTVJ3vxQYmeEuKFbCoQqOJ THeuHNUg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nzHOT-00DYAI-Hj; Thu, 09 Jun 2022 12:36:09 +0000 Date: Thu, 9 Jun 2022 13:36:09 +0100 From: Matthew Wilcox To: Nikolay Borisov Cc: David Sterba , linux-btrfs@vger.kernel.org Subject: Re: [PATCH] btrfs: use preallocated page for super block write Message-ID: References: <20220607154229.9164-1-dsterba@suse.com> <1c8faef3-6ccb-6eb8-6f42-d52faf8f74e1@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1c8faef3-6ccb-6eb8-6f42-d52faf8f74e1@suse.com> Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Thu, Jun 09, 2022 at 10:30:06AM +0300, Nikolay Borisov wrote: > nit: I think it's important to remark in the changelog that with this change > sb writing becomes sequential as opposed to parallel with the old code. This > also means that wait_dev_supers can be simplified because the max_mirror's > loop is not needed, at least for waiting, since for each device we at most > need to wait for the last write to it, as all previous ones have been > serialized by the pagelock. I've just re-read the patch very carefully three times, and I don't see the change that makes this happen. Can you explain to me how it happens?