From nobody Fri Dec 19 11:32:26 2025 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) (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 AAB4E3A1A9; Mon, 18 Dec 2023 14:14:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.194]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4Sv1zg1CjNzMnxK; Mon, 18 Dec 2023 22:14:39 +0800 (CST) Received: from dggpeml500021.china.huawei.com (unknown [7.185.36.21]) by mail.maildlp.com (Postfix) with ESMTPS id 3F89014040D; Mon, 18 Dec 2023 22:14:52 +0800 (CST) Received: from huawei.com (10.175.127.227) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Mon, 18 Dec 2023 22:14:51 +0800 From: Baokun Li To: CC: , , , , , , , , , Subject: [PATCH 3/4] ext4: avoid bb_free and bb_fragments inconsistency in mb_free_blocks() Date: Mon, 18 Dec 2023 22:18:13 +0800 Message-ID: <20231218141814.1477338-4-libaokun1@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20231218141814.1477338-1-libaokun1@huawei.com> References: <20231218141814.1477338-1-libaokun1@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500021.china.huawei.com (7.185.36.21) Content-Type: text/plain; charset="utf-8" After updating bb_free in mb_free_blocks, it is possible to return without updating bb_fragments because the block being freed is found to have already been freed, which leads to inconsistency between bb_free and bb_fragments. Since the group may be unlocked in ext4_grp_locked_error(), this can lead to problems such as dividing by zero when calculating the average fragment length. Therefore, to ensure consistency, move the update of bb_free to after the block double-free check. Fixes: eabe0444df90 ("ext4: speed-up releasing blocks on commit") CC: stable@vger.kernel.org # 3.10 Signed-off-by: Baokun Li --- fs/ext4/mballoc.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index a95fa6e2b0f9..2fbee0f0f5c3 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1892,11 +1892,6 @@ static void mb_free_blocks(struct inode *inode, stru= ct ext4_buddy *e4b, mb_check_buddy(e4b); mb_free_blocks_double(inode, e4b, first, count); =20 - this_cpu_inc(discard_pa_seq); - e4b->bd_info->bb_free +=3D count; - if (first < e4b->bd_info->bb_first_free) - e4b->bd_info->bb_first_free =3D first; - /* access memory sequentially: check left neighbour, * clear range and then check right neighbour */ @@ -1922,9 +1917,14 @@ static void mb_free_blocks(struct inode *inode, stru= ct ext4_buddy *e4b, sb, e4b->bd_group, EXT4_GROUP_INFO_BBITMAP_CORRUPT); } - goto done; + return; } =20 + this_cpu_inc(discard_pa_seq); + e4b->bd_info->bb_free +=3D count; + if (first < e4b->bd_info->bb_first_free) + e4b->bd_info->bb_first_free =3D first; + /* let's maintain fragments counter */ if (left_is_free && right_is_free) e4b->bd_info->bb_fragments--; @@ -1949,7 +1949,6 @@ static void mb_free_blocks(struct inode *inode, struc= t ext4_buddy *e4b, if (first <=3D last) mb_buddy_mark_free(e4b, first >> 1, last >> 1); =20 -done: mb_set_largest_free_order(sb, e4b->bd_info); mb_update_avg_fragment_size(sb, e4b->bd_info); mb_check_buddy(e4b); --=20 2.31.1