From patchwork Tue Nov 24 14:44:13 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nikolay Borisov X-Patchwork-Id: 11929157 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 105AFC2D0E4 for ; Tue, 24 Nov 2020 14:44:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B2123206F9 for ; Tue, 24 Nov 2020 14:44:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="FblKEmvY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389227AbgKXOoQ (ORCPT ); Tue, 24 Nov 2020 09:44:16 -0500 Received: from mx2.suse.de ([195.135.220.15]:39690 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388162AbgKXOoP (ORCPT ); Tue, 24 Nov 2020 09:44:15 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1606229054; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=ue3oTddZ78Vaf06m9DggVdbjoALwN50Ro1tqvxTXT2M=; b=FblKEmvYcLnbNpguk+IaSKdPLMu9hAQZSOEEl8lOBhliWWZNKUMRW1RjDJDSYwb5Qv9g54 d4jIeeEOwbLzF7KgSa+1x16qIgLs4XahRwhgf6AJPovIMpTgJNLoclvmlB+7WeeT4qs9NS kb6jy4Dy/p4ZFpP7Rr5+XAF76V6PdYs= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id A035CAC55; Tue, 24 Nov 2020 14:44:14 +0000 (UTC) From: Nikolay Borisov To: linux-btrfs@vger.kernel.org Cc: Nikolay Borisov Subject: [PATCH] btrfs: Annotate unlocked accesses to transaction state Date: Tue, 24 Nov 2020 16:44:13 +0200 Message-Id: <20201124144413.3168075-1-nborisov@suse.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org btrfs_transaction::state is protected by btrfs_fs_info::trans_lock and all accesses to this variable should be synchornized by it. However, there are 2 exceptions, namely checking if currently running transaction has entered its commit phase in start_transaction and in btrfs_should_end_transaction. Annotate those 2, unlocked accesses with READ_ONCE respectively. Also remove the full memory barrier in start_transaction as it provides no ordering guarantees due to being unpaired. All other accsess to transaction state happen under trans_lock being held. Signed-off-by: Nikolay Borisov --- fs/btrfs/transaction.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) -- 2.25.1 diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index df5687a92798..e5a5c3604a9b 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -695,8 +695,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, h->can_flush_pending_bgs = true; INIT_LIST_HEAD(&h->new_bgs); - smp_mb(); - if (cur_trans->state >= TRANS_STATE_COMMIT_START && + if (READ_ONCE(cur_trans->state) >= TRANS_STATE_COMMIT_START && may_wait_transaction(fs_info, type)) { current->journal_info = h; btrfs_commit_transaction(h); @@ -912,7 +911,7 @@ int btrfs_should_end_transaction(struct btrfs_trans_handle *trans) { struct btrfs_transaction *cur_trans = trans->transaction; - if (cur_trans->state >= TRANS_STATE_COMMIT_START || + if (READ_ONCE(cur_trans->state) >= TRANS_STATE_COMMIT_START || test_bit(BTRFS_DELAYED_REFS_FLUSHING, &cur_trans->delayed_refs.flags)) return 1;