From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DB0FA289814; Mon, 5 May 2025 23:14:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746486855; cv=none; b=XsgcxTELNZruFIjZJliHleVIb4YRz43aUBBxUFhsfb7dedmumwrGlI6/G83UXfiLe19OhE/d7gqvFGQSsTVmrME43fssJpDEjyjKMjZng5W4JZxdsWehk8PSL5ww7y1QereA2ZYaBmEVRioAKeaAOfqxOd/vfiIbF59knbUyD1I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746486855; c=relaxed/simple; bh=s+ZfrJjM3RpUKvwA0vh4TV7sKihjCFt1G/jJEXc13bw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=lwKQOJiOhHXAOCd/SDBGmABQyfkrSpCt3tDWFeId2ZqSfnfNMAv/JSyqv6n0lHwIcp5f+ALPE94eum2EYoH9t7oJLkTFbD/T9r4mtE2GS+rfcMmRLeSnKq0Diz2Z1agWe+Hg4hdusDW8GTPK0f6uMWFl6w32nOUtYA16P0rFyqQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P1prZM19; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="P1prZM19" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BFF72C4CEE4; Mon, 5 May 2025 23:14:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746486854; bh=s+ZfrJjM3RpUKvwA0vh4TV7sKihjCFt1G/jJEXc13bw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P1prZM19GC6Uwdxu/g+29qHHIzZwAQb8GroZRFvcbWH0d5GF8bqkqEUj5isZnIP4J 85oTkFavhfoBWWaOiJu7FHULKtpMONRrU8y2G6eC6iNkc1yzliRfLdZxJHh7PbR7gN w75yZhN7m48q6JdT5Xr1KSjs7PlUMaBzXQopOv9fLNYurBA8ysqRmeEVIP++1EXprR CeH04BkUGAHZO4TIJf8lJmAwA3Q0vkSss8p5IhdE5hRxPKFqXbqwMAdmAk3pPg6Rhr ZqrytEeYzwvdB+MDyyXPdcBvjY/qwFON74o8V8LkiZR+R6Z9lE0uM3BdfQa0OssZ5F F5ICZCAq9QUZA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Filipe Manana , Johannes Thumshirn , David Sterba , Sasha Levin , clm@fb.com, josef@toxicpanda.com, linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 5.15 026/153] btrfs: get zone unusable bytes while holding lock at btrfs_reclaim_bgs_work() Date: Mon, 5 May 2025 19:11:13 -0400 Message-Id: <20250505231320.2695319-26-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250505231320.2695319-1-sashal@kernel.org> References: <20250505231320.2695319-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.15.181 Content-Transfer-Encoding: 8bit From: Filipe Manana [ Upstream commit 1283b8c125a83bf7a7dbe90c33d3472b6d7bf612 ] At btrfs_reclaim_bgs_work(), we are grabbing a block group's zone unusable bytes while not under the protection of the block group's spinlock, so this can trigger race reports from KCSAN (or similar tools) since that field is typically updated while holding the lock, such as at __btrfs_add_free_space_zoned() for example. Fix this by grabbing the zone unusable bytes while we are still in the critical section holding the block group's spinlock, which is right above where we are currently grabbing it. Reviewed-by: Johannes Thumshirn Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/block-group.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c index 2c5bd2ad69f35..614917cac0e7e 100644 --- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -1543,6 +1543,17 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) up_write(&space_info->groups_sem); goto next; } + + /* + * Cache the zone_unusable value before turning the block group + * to read only. As soon as the block group is read only it's + * zone_unusable value gets moved to the block group's read-only + * bytes and isn't available for calculations anymore. We also + * cache it before unlocking the block group, to prevent races + * (reports from KCSAN and such tools) with tasks updating it. + */ + zone_unusable = bg->zone_unusable; + spin_unlock(&bg->lock); /* @@ -1558,13 +1569,6 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) goto next; } - /* - * Cache the zone_unusable value before turning the block group - * to read only. As soon as the blog group is read only it's - * zone_unusable value gets moved to the block group's read-only - * bytes and isn't available for calculations anymore. - */ - zone_unusable = bg->zone_unusable; ret = inc_block_group_ro(bg, 0); up_write(&space_info->groups_sem); if (ret < 0) -- 2.39.5