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 97A15C43219 for ; Tue, 11 Oct 2022 14:54:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230376AbiJKOyI (ORCPT ); Tue, 11 Oct 2022 10:54:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230050AbiJKOxF (ORCPT ); Tue, 11 Oct 2022 10:53:05 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83FB49AFCA; Tue, 11 Oct 2022 07:51:17 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 36852611C6; Tue, 11 Oct 2022 14:51:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B99B9C433C1; Tue, 11 Oct 2022 14:51:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665499876; bh=m5XLNmell0PrmFO8ifP66AP9KRaK8RMcLJHNEUlfM0Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=L9v+QSpCGQBdxjwMnPQ0DdivuRJtHhVBm72NwUn3JNEg6CQaAZERrP09HXSPdpoG/ JXiqr8lARkSLnVsfjrgPneVnI5hW/hIy85tDjOJCUrxD+ZhZST/HrX36l8NmPKQbta C4EAAgjH90Y+Bt2n9x+AaB3I28a8vfuWbS+uNFAxHRq2ZW/3nOTUG9lybCQd+1HOYz jR2Qo7FG3ZMrwNqMcNDbU3ZQULM0CJDghEggo+y5NdbyQyu/y4HQXDZYh8ArjdAbyb qBPpyKCDkpd4v6PCuQAu/1QUsDdqWObPnWD3TL+wi25SPYTSCDVoI6xQ17AX0AvldW C+fsEw80Z44hA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: David Sterba , Zygo Blaxell , Sasha Levin , clm@fb.com, josef@toxicpanda.com, linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 6.0 39/46] btrfs: add KCSAN annotations for unlocked access to block_rsv->full Date: Tue, 11 Oct 2022 10:50:07 -0400 Message-Id: <20221011145015.1622882-39-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221011145015.1622882-1-sashal@kernel.org> References: <20221011145015.1622882-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: David Sterba [ Upstream commit 748f553c3c4c4f175c6c834358632aff802d72cf ] KCSAN reports that there's unlocked access mixed with locked access, which is technically correct but is not a bug. To avoid false alerts at least from KCSAN, add annotation and use a wrapper whenever ->full is accessed for read outside of lock. It is used as a fast check and only advisory. In the worst case the block reserve is found !full and becomes full in the meantime, but properly handled. Depending on the value of ->full, btrfs_block_rsv_release decides where to return the reservation, and block_rsv_release_bytes handles a NULL pointer for block_rsv and if it's not NULL then it double checks the full status under a lock. Link: https://lore.kernel.org/linux-btrfs/CAAwBoOJDjei5Hnem155N_cJwiEkVwJYvgN-tQrwWbZQGhFU=cA@mail.gmail.com/ Link: https://lore.kernel.org/linux-btrfs/YvHU/vsXd7uz5V6j@hungrycats.org Reported-by: Zygo Blaxell Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/block-rsv.c | 2 +- fs/btrfs/block-rsv.h | 9 +++++++++ fs/btrfs/transaction.c | 4 ++-- 3 files changed, 12 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c index 06be0644dd37..046caf14a4bb 100644 --- a/fs/btrfs/block-rsv.c +++ b/fs/btrfs/block-rsv.c @@ -286,7 +286,7 @@ u64 btrfs_block_rsv_release(struct btrfs_fs_info *fs_info, */ if (block_rsv == delayed_rsv) target = global_rsv; - else if (block_rsv != global_rsv && !delayed_rsv->full) + else if (block_rsv != global_rsv && !btrfs_block_rsv_full(delayed_rsv)) target = delayed_rsv; if (target && block_rsv->space_info != target->space_info) diff --git a/fs/btrfs/block-rsv.h b/fs/btrfs/block-rsv.h index 0c183709be00..578c3497a455 100644 --- a/fs/btrfs/block-rsv.h +++ b/fs/btrfs/block-rsv.h @@ -92,4 +92,13 @@ static inline void btrfs_unuse_block_rsv(struct btrfs_fs_info *fs_info, btrfs_block_rsv_release(fs_info, block_rsv, 0, NULL); } +/* + * Fast path to check if the reserve is full, may be carefully used outside of + * locks. + */ +static inline bool btrfs_block_rsv_full(const struct btrfs_block_rsv *rsv) +{ + return data_race(rsv->full); +} + #endif /* BTRFS_BLOCK_RSV_H */ diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 4c87bf2abc14..49570ad23f2e 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -594,7 +594,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, */ num_bytes = btrfs_calc_insert_metadata_size(fs_info, num_items); if (flush == BTRFS_RESERVE_FLUSH_ALL && - delayed_refs_rsv->full == 0) { + btrfs_block_rsv_full(delayed_refs_rsv) == 0) { delayed_refs_bytes = num_bytes; num_bytes <<= 1; } @@ -619,7 +619,7 @@ start_transaction(struct btrfs_root *root, unsigned int num_items, if (rsv->space_info->force_alloc) do_chunk_alloc = true; } else if (num_items == 0 && flush == BTRFS_RESERVE_FLUSH_ALL && - !delayed_refs_rsv->full) { + !btrfs_block_rsv_full(delayed_refs_rsv)) { /* * Some people call with btrfs_start_transaction(root, 0) * because they can be throttled, but have some other mechanism -- 2.35.1