From patchwork Thu Aug 6 07:29:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 11702803 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A25ED17CB for ; Thu, 6 Aug 2020 11:04:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A36DF221E2 for ; Thu, 6 Aug 2020 11:04:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728666AbgHFH3V (ORCPT ); Thu, 6 Aug 2020 03:29:21 -0400 Received: from mx2.suse.de ([195.135.220.15]:60366 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727105AbgHFH3T (ORCPT ); Thu, 6 Aug 2020 03:29:19 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3B2D1ADB3 for ; Thu, 6 Aug 2020 07:29:35 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH] btrfs-progs: docs: update the stability and performance status of quota Date: Thu, 6 Aug 2020 15:29:06 +0800 Message-Id: <20200806072906.358641-1-wqu@suse.com> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org There are a lot of enhancement to btrfs quota through v5.x releases. Now btrfs quota is more stable than it used to be. So update the man page to relect this. Signed-off-by: Qu Wenruo Reviewed-by: Neal Gompa --- Documentation/btrfs-quota.asciidoc | 43 +++++++++++++++++++++++++----- 1 file changed, 37 insertions(+), 6 deletions(-) diff --git a/Documentation/btrfs-quota.asciidoc b/Documentation/btrfs-quota.asciidoc index 85ebf729c2fa..1c032f11d001 100644 --- a/Documentation/btrfs-quota.asciidoc +++ b/Documentation/btrfs-quota.asciidoc @@ -23,16 +23,47 @@ PERFORMANCE IMPLICATIONS ~~~~~~~~~~~~~~~~~~~~~~~~ When quotas are activated, they affect all extent processing, which takes a -performance hit. Activation of qgroups is not recommended unless the user -intends to actually use them. +performance hit. + +Under most cases, the performance hit should be more or less acceptable for +root fs usage. + +There used to be a huge performance hit for balance with quota enabled. +That problem is solved since v5.4 kernel. STABILITY STATUS ~~~~~~~~~~~~~~~~ -The qgroup implementation has turned out to be quite difficult as it affects -the core of the filesystem operation. Qgroup users have hit various corner cases -over time, such as incorrect accounting or system instability. The situation is -gradually improving and issues found and fixed. +Btrfs quota has different stablity for different functionality: + +Extent accounting +^^^^^^^^^^^^^^^^^ + +Pretty stable, there aren't many bugs (if any) affecting the extent accounting +through v5.x release cycles. + +Thus if users just want referenced/exclusive usage of each subvolume, it +should be safe to use. + +Limit +^^^^^ + +Should be near stable since v5.9. + +There used to be some bugs causing early EDQUOT errors before v5.9. +But v5.9 should solve them quite well, along with extra safe nets catching any +reserved space leakage. + +Corner cases and small fixes may pop up time by time, but the core limit +functionality should be in good shape since v5.9. + +Multi-level qgroups +^^^^^^^^^^^^^^^^^^^ + +Needs more testing. Although the core extent accounting should also work well +for higher level qgroups, we don't have good enough test coverage yet. + +Thus extra testing and bug reports are welcomed. HIERARCHICAL QUOTA GROUP CONCEPTS ---------------------------------