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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E45E2C33CB1 for ; Thu, 16 Jan 2020 06:04:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BFA4E20748 for ; Thu, 16 Jan 2020 06:04:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729710AbgAPGEO (ORCPT ); Thu, 16 Jan 2020 01:04:14 -0500 Received: from mx2.suse.de ([195.135.220.15]:45134 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727026AbgAPGEN (ORCPT ); Thu, 16 Jan 2020 01:04:13 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id B20C1B1A3 for ; Thu, 16 Jan 2020 06:04:11 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v6 0/4] Introduce per-profile available space array to avoid over-confident can_overcommit() Date: Thu, 16 Jan 2020 14:03:59 +0800 Message-Id: <20200116060404.95200-1-wqu@suse.com> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org There are several bug reports of ENOSPC error in btrfs_run_delalloc_range(). With some extra info from one reporter, it turns out that can_overcommit() is using a wrong way to calculate allocatable metadata space. The most typical case would look like: devid 1 unallocated: 1G devid 2 unallocated: 10G metadata profile: RAID1 In above case, we can at most allocate 1G chunk for metadata, due to unbalanced disk free space. But current can_overcommit() uses factor based calculation, which never consider the disk free space balance. To address this problem, here comes the per-profile available space array, which gets updated every time a chunk get allocated/removed or a device get grown or shrunk. This provides a quick way for hotter place like can_overcommit() to grab an estimation on how many bytes it can over-commit. The per-profile available space calculation tries to keep the behavior of chunk allocator, thus it can handle uneven disks pretty well. And statfs() can also grab that pre-calculated value for instance usage. For metadata over-commit, statfs() falls back to factor based educated guess method. Since over-commit can only happen when we have unallocated space, the problem caused by over-commit should only be a first world problem. Since this patch introduced a new failure pattern, some new error handling are introduced: - __btrfs_alloc_chunk() At the end of that function where calc_per_profile_avail() get called, if it failed due to -ENOMEM, we will revert device used space, and remove the allocated chunk. This is the only new error handling added by patch 5. - btrfs_remove_chunk() There is no good way to revert the change. So here we abort transaction, just like what the old error handling does. - btrfs_grow_device() This function has its problem by not reverting device used space from the very beginning. This patchset will enhance it in patch 4. - btrfs_shrink_device() This function already has good error handling, reuse it. - btrfs_verify_dev_extents() Mount time error will lead to mount failure, nothing to worry about. Contents of the patchset: Patch 1: Core facility, with basic (not perfect) error handling Patch 2: Fix for over-confident can_overcommit() Patch 3: Make statfs() more accurate Patch 4: Better error handling for btrfs_grow_device() Patch 5: Better error handling for __btrfs_alloc_chunk() If needed, patch 4 and patch 5 can be merged into patch 1. Changelog: v1: - Fix a bug where we forgot to update per-profile array after allocating a chunk. To avoid ABBA deadlock, this introduce a small windows at the end __btrfs_alloc_chunk(), it's not elegant but should be good enough before we rework chunk and device list mutex. - Make statfs() to use virtual chunk allocator to do better estimation Now statfs() can report not only more accurate result, but can also handle RAID5/6 better. v2: - Fix a deadlock caused by acquiring device_list_mutex under __btrfs_alloc_chunk() There is no need to acquire device_list_mutex when holding chunk_mutex. Fix it and remove the lockdep assert. v3: - Use proper chunk_mutex instead of device_list_mutex Since they are protecting two different things, and we only care about alloc_list, we should only use chunk_mutex. With improved lock situation, it's easier to fold calc_per_profile_available() calls into the first patch. - Add performance benchmark for statfs() modification As Facebook seems to run into some problems with statfs() calls, add some basic ftrace results. v4: - Keep the lock-free design for statfs() As extra sleeping in statfs() may not be a good idea, keep the old lock-free design, and use factor based calculation as fall back. v5: - Enhance btrfs_update_device() error handling in btrfs_grow_device() - Ensure all failure caused by calc_per_profile_available() is the same with existing error handling - Fix a bug where chunk_mutex is not released in btrfs_shrink_device() v6: - Don't update the array if we hit any error. To avoid calling calc_per_profile_avail() in error handling path. - Re-order the patchset Make the core facility the first patch. Error handling improvement in later patches. - Add better error handling Improve one existing bad error handling, and provide a better solution for __btrfs_alloc_chunk() Qu Wenruo (5): btrfs: Introduce per-profile available space facility btrfs: space-info: Use per-profile available space in can_overcommit() btrfs: statfs: Use pre-calculated per-profile available space btrfs: Reset device size when btrfs_update_device() failed in btrfs_grow_device() btrfs: volumes: Revert device used bytes when calc_per_profile_avail() failed fs/btrfs/space-info.c | 15 ++- fs/btrfs/super.c | 182 +++++++++---------------------- fs/btrfs/volumes.c | 245 ++++++++++++++++++++++++++++++++++++++---- fs/btrfs/volumes.h | 11 ++ 4 files changed, 290 insertions(+), 163 deletions(-) -- 2.24.1