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 A9D40C433EF for ; Thu, 14 Jul 2022 13:46:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239008AbiGNNqx (ORCPT ); Thu, 14 Jul 2022 09:46:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42868 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231811AbiGNNqw (ORCPT ); Thu, 14 Jul 2022 09:46:52 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D114F52FD1 for ; Thu, 14 Jul 2022 06:46:50 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 87B4B34982; Thu, 14 Jul 2022 13:46:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1657806409; h=from:from:reply-to: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=TJp6zdzOYqptDeclJKKhdIaxyPTzN16LaSy8KJInTQo=; b=Ux4ZEBNnfxrFyJyNO72E9M5Q1TZNDbiNhRpYhErtJgKsBILmMGKvb+L5eTJk6svydF3AUZ pzxy2QCk/D/qlMJJpOlAdahcMSh8lXKtZSicc9UQq4hFGsPIG2v1BUaZ8RAF4GeAN0sxPM W84o20cHRkWEuMCPHPcO+jRMBQM5J0s= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1657806409; h=from:from:reply-to: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=TJp6zdzOYqptDeclJKKhdIaxyPTzN16LaSy8KJInTQo=; b=ff62T8hf2uY3dHV904xwHu416PUyMwfXKyZZemAqfeSGN0ZOrmQcxBQciOITDjOuYXneSx kgH/hEbuEOaEEnAg== Received: from quack3.suse.cz (unknown [10.100.224.230]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 7591B2C141; Thu, 14 Jul 2022 13:46:49 +0000 (UTC) Received: by quack3.suse.cz (Postfix, from userid 1000) id 0515BA0659; Thu, 14 Jul 2022 15:46:45 +0200 (CEST) Date: Thu, 14 Jul 2022 15:46:45 +0200 From: Jan Kara To: "Kiselev, Oleg" Cc: "linux-ext4@vger.kernel.org" , Theodore Ts'o Subject: Re: [PATCH 1/2] ext4: reduce computation of overhead during resize Message-ID: <20220714134645.r4gqax4au5el2pox@quack3> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu 30-06-22 02:17:21, Kiselev, Oleg wrote: > This patch avoids doing an O(n**2)-complexity walk through every flex group. > Instead, it uses the already computed overhead information for the newly > allocated space, and simply adds it to the previously calculated > overhead stored in the superblock. This drastically reduces the time > taken to resize very large bigalloc filesystems (from 3+ hours for a > 64TB fs down to milliseconds). > > Signed-off-by: Oleg Kiselev > --- > fs/ext4/resize.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) Overall this looks fine, a few smaller comments below. > > diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c > index 8b70a4701293..2acc9fca99ea 100644 > --- a/fs/ext4/resize.c > +++ b/fs/ext4/resize.c > @@ -1380,6 +1380,16 @@ static int ext4_setup_new_descs(handle_t *handle, struct super_block *sb, > return err; > } > > +static void ext4_set_overhead(struct super_block *sb, > + const ext4_grpblk_t overhead) > +{ ext4_add_overhead() would be a better name I suppose. Also the 'overhead' should rather be ext4_fsblk_t to be on the safe side... > + struct ext4_sb_info *sbi = EXT4_SB(sb); > + struct ext4_super_block *es = sbi->s_es; Empty line between variable declarations and the code please. > + sbi->s_overhead += overhead; > + es->s_overhead_clusters = cpu_to_le32((unsigned long) sbi->s_overhead); ^^^ the typecast looks bogus here... > + smp_wmb(); > +} The barrier without any comment makes me really wonder why it is here... But I get ext4_calculate_overhead() has is as well so you're just keeping it. > + > /* > * ext4_update_super() updates the super block so that the newly added > * groups can be seen by the filesystem. > @@ -1482,8 +1492,16 @@ static void ext4_update_super(struct super_block *sb, > > /* > * Update the fs overhead information > + * > + * For bigalloc, if the superblock already has a properly calculated > + * overhead, update it wth a value based on numbers already computed ^^ with > + * above for the newly allocated capacity. > */ > - ext4_calculate_overhead(sb); > + if (ext4_has_feature_bigalloc(sb) && (sbi->s_overhead != 0)) > + ext4_set_overhead(sb, > + EXT4_NUM_B2C(sbi, blocks_count - free_blocks)); > + else > + ext4_calculate_overhead(sb); > > if (test_opt(sb, DEBUG)) > printk(KERN_DEBUG "EXT4-fs: added group %u:" Honza -- Jan Kara SUSE Labs, CR