From nobody Tue Dec 2 01:54:22 2025 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) (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 6F7432FF670; Fri, 21 Nov 2025 06:10:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763705436; cv=none; b=FQjdEjcQ57CMMvPS0LedW2srj5E/Z/hSKd524kvhvU1fzYYo0yOz3vwZS2QnTLGEM78e7sGN2HrAm0KLj2Dw3KOUjwCNMpf80lKZBxFc05jh8CfhU7F5yTuXzdy/OmVa8EJpz2otwZdW7gnQewk4kuWWpWTTi9/m614JDEGd0jg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763705436; c=relaxed/simple; bh=tfElMXijn9LujEgOHitaRMBO3gvCAdVQNYKSPpQ6oT8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lAFoWZl8X5RoReTlnBrotGpuZPiCqW/rj4dQWsytKKsq8QoluZ2CJqg7GA4WLx6ZxbqUf9bALK0PW7vRIY99jf+NmKzFi3qt03SxDVOnE3pcKyZHbZ/yycew5nWMeN8jqeeih3sfZe+Lu1T1cNACNppt9JLD6wxjHg9pE4+P78I= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=none smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4dCPvS0cLVzKHLy4; Fri, 21 Nov 2025 14:09:56 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id D5CDB1A1A35; Fri, 21 Nov 2025 14:10:26 +0800 (CST) Received: from huaweicloud.com (unknown [10.50.85.155]) by APP2 (Coremail) with SMTP id Syh0CgD3VHtAAiBp_of0BQ--.63807S11; Fri, 21 Nov 2025 14:10:26 +0800 (CST) From: Zhang Yi To: linux-ext4@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz, yi.zhang@huawei.com, yi.zhang@huaweicloud.com, yizhang089@gmail.com, libaokun1@huawei.com, yangerkun@huawei.com Subject: [PATCH v2 07/13] ext4: drop extent cache before splitting extent Date: Fri, 21 Nov 2025 14:08:05 +0800 Message-ID: <20251121060811.1685783-8-yi.zhang@huaweicloud.com> X-Mailer: git-send-email 2.46.1 In-Reply-To: <20251121060811.1685783-1-yi.zhang@huaweicloud.com> References: <20251121060811.1685783-1-yi.zhang@huaweicloud.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-CM-TRANSID: Syh0CgD3VHtAAiBp_of0BQ--.63807S11 X-Coremail-Antispam: 1UD129KBjvJXoW7Ww4fur4xKFyDCrW7Wr15urg_yoW8Kr17pa s2kF1DGr4kA34vg34fG3WDKr1kuw1kGrW7ArW5Gw1jv3WDGryakrn7GayUZFySgFW8ZF15 Zr48ta45Ga4DJFJanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUmI14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkE bVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67 AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI 42IY6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCw CI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnI WIevJa73UjIFyTuYvjfUOyIUUUUUU X-CM-SenderInfo: d1lo6xhdqjqx5xdzvxpfor3voofrz/ Content-Type: text/plain; charset="utf-8" From: Zhang Yi When splitting an unwritten extent in the middle and converting it to initialized in ext4_split_extent() with the EXT4_EXT_MAY_ZEROOUT and EXT4_EXT_DATA_VALID2 flags set, it could leave a stale unwritten extent. Assume we have an unwritten file and buffered write in the middle of it without dioread_nolock enabled, it will allocate blocks as written extent. 0 A B N [UUUUUUUUUUUU] on-disk extent U: unwritten extent [UUUUUUUUUUUU] extent status tree [--DDDDDDDD--] D: valid data |<- ->| ----> this range needs to be initialized ext4_split_extent() first try to split this extent at B with EXT4_EXT_DATA_PARTIAL_VALID1 and EXT4_EXT_MAY_ZEROOUT flag set, but ext4_split_extent_at() failed to split this extent due to temporary lack of space. It zeroout B to N and leave the entire extent as unwritten. 0 A B N [UUUUUUUUUUUU] on-disk extent [UUUUUUUUUUUU] extent status tree [--DDDDDDDDZZ] Z: zeroed data ext4_split_extent() then try to split this extent at A with EXT4_EXT_DATA_VALID2 flag set. This time, it split successfully and leave an written extent from A to N. 0 A B N [UU|WWWWWWWWWW] on-disk extent W: written extent [UU|UUUUUUUUUU] extent status tree [--|DDDDDDDDZZ] Finally ext4_map_create_blocks() only insert extent A to B to the extent status tree, and leave an stale unwritten extent in the status tree. 0 A B N [UU|WWWWWWWWWW] on-disk extent W: written extent [UU|WWWWWWWWUU] extent status tree [--|DDDDDDDDZZ] Fix this issue by always remove cached extent status entry before splitting extent. Signed-off-by: Zhang Yi --- fs/ext4/extents.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 2b5aec3f8882..9bb80af4b5cf 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3367,6 +3367,12 @@ static struct ext4_ext_path *ext4_split_extent(handl= e_t *handle, ee_len =3D ext4_ext_get_actual_len(ex); unwritten =3D ext4_ext_is_unwritten(ex); =20 + /* + * Drop extent cache to prevent stale unwritten extents remaining + * after zeroing out. + */ + ext4_es_remove_extent(inode, ee_block, ee_len); + /* Do not cache extents that are in the process of being modified. */ flags |=3D EXT4_EX_NOCACHE; =20 --=20 2.46.1