From nobody Thu Apr 2 19:04:18 2026 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 556C43DA7DD; Fri, 27 Mar 2026 10:34:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774607683; cv=none; b=dGUjYtlPlSvG8bTIck16V7taoLA3fVCiBf9cbEU5GWjff38JHEDLbXXnEu4Ds5gHqvKTX6M1XNq/K+mLZ1CwDCDkzt0LrzeBkGR5IinCUrpbGsizINQdj5d5bMzl6IpMIwJV2o61QYsqBOKIs4dxD1s1VIWXDk8ozehtOqiXQ54= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774607683; c=relaxed/simple; bh=HWHjJwruyHq/Wbz4i5l0dAiCgRGI7Sfz7pY8baZw8Ns=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cDpCDvZOWib5BVHRLQqkVMmw2Wx9iQX39Oqs/4P5NIKZtR7G2jj5o0idb9zMkxyU6xOsKVh0mGbePsm2d52rL+YlJAqAAbBJu6VKTA6LUJicTX+8utTG7Jp/MoZ2jJceCQVadc5ZHp5aviQyIwfQ8BOERupbxwaXIkcaPoRJwHo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.170]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4fhxpM2wlMzYQv8r; Fri, 27 Mar 2026 18:34:19 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 03C0E4056F; Fri, 27 Mar 2026 18:34:33 +0800 (CST) Received: from huaweicloud.com (unknown [10.50.85.155]) by APP1 (Coremail) with SMTP id cCh0CgC3utouXcZp_T2cCQ--.28730S17; Fri, 27 Mar 2026 18:34:32 +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, ojaswin@linux.ibm.com, ritesh.list@gmail.com, libaokun@linux.alibaba.com, yi.zhang@huawei.com, yi.zhang@huaweicloud.com, yizhang089@gmail.com, yangerkun@huawei.com, yukuai@fnnas.com Subject: [PATCH v4 13/13] ext4: zero post-EOF partial block before appending write Date: Fri, 27 Mar 2026 18:29:39 +0800 Message-ID: <20260327102939.1095257-14-yi.zhang@huaweicloud.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260327102939.1095257-1-yi.zhang@huaweicloud.com> References: <20260327102939.1095257-1-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: cCh0CgC3utouXcZp_T2cCQ--.28730S17 X-Coremail-Antispam: 1UD129KBjvJXoWxGrW8WrWrtryxZr17Gr1Dtrb_yoWrWFW3pF ZIkF1fuwnFgr9rW3yxGFsrX34jka48JrW7GFyfKrWfZFnxJw18KF1Iq34UtFWrtrZrXa1F qF4qkFyUG3Wjy3DanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUmS14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUGVWUXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkE bVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67 AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVW8JVW5JwCI 42IY6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF 4lIxAIcVC2z280aVAFwI0_Gr0_Cr1lIxAIcVC2z280aVCY1x0267AKxVW8Jr0_Cr1UYxBI daVFxhVjvjDU0xZFpf9x0JUWMKtUUUUU= X-CM-SenderInfo: d1lo6xhdqjqx5xdzvxpfor3voofrz/ Content-Type: text/plain; charset="utf-8" From: Zhang Yi In cases of appending write beyond EOF, ext4_zero_partial_blocks() is called within ext4_*_write_end() to zero out the partial block beyond EOF. This prevents exposing stale data that might be written through mmap. However, supporting only the regular buffered write path is insufficient. It is also necessary to support the DAX path as well as the upcoming iomap buffered write path. Therefore, move this operation to ext4_write_checks(). In addition, this may introduce a race window in which a post-EOF buffered write can race with an mmap write after the old EOF block has been zeroed. As a result, the data in this block written by the buffer-write and the data written by the mmap-write may be mixed. However, this is safe because users should not rely on the result of the race condition. Signed-off-by: Zhang Yi Reviewed-by: Jan Kara --- fs/ext4/file.c | 17 +++++++++++++++++ fs/ext4/inode.c | 21 +++++++-------------- 2 files changed, 24 insertions(+), 14 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index f1dc5ce791a7..ec0d81bea07a 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -271,6 +271,8 @@ static ssize_t ext4_generic_write_checks(struct kiocb *= iocb, =20 static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from) { + struct inode *inode =3D file_inode(iocb->ki_filp); + loff_t old_size =3D i_size_read(inode); ssize_t ret, count; =20 count =3D ext4_generic_write_checks(iocb, from); @@ -280,6 +282,21 @@ static ssize_t ext4_write_checks(struct kiocb *iocb, s= truct iov_iter *from) ret =3D file_modified(iocb->ki_filp); if (ret) return ret; + + /* + * If the position is beyond the EOF, it is necessary to zero out the + * partial block that beyond the existing EOF, as it may contains + * stale data written through mmap. + */ + if (iocb->ki_pos > old_size && !ext4_verity_in_progress(inode)) { + if (iocb->ki_flags & IOCB_NOWAIT) + return -EAGAIN; + + ret =3D ext4_block_zero_eof(inode, old_size, iocb->ki_pos); + if (ret) + return ret; + } + return count; } =20 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 3b150e643ef5..7afa5fbf067b 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1456,10 +1456,9 @@ static int ext4_write_end(const struct kiocb *iocb, folio_unlock(folio); folio_put(folio); =20 - if (old_size < pos && !verity) { + if (old_size < pos && !verity) pagecache_isize_extended(inode, old_size, pos); - ext4_block_zero_eof(inode, old_size, pos); - } + /* * Don't mark the inode dirty under folio lock. First, it unnecessarily * makes the holding time of folio lock longer. Second, it forces lock @@ -1574,10 +1573,8 @@ static int ext4_journalled_write_end(const struct ki= ocb *iocb, folio_unlock(folio); folio_put(folio); =20 - if (old_size < pos && !verity) { + if (old_size < pos && !verity) pagecache_isize_extended(inode, old_size, pos); - ext4_block_zero_eof(inode, old_size, pos); - } =20 if (size_changed) { ret2 =3D ext4_mark_inode_dirty(handle, inode); @@ -3196,7 +3193,7 @@ static int ext4_da_do_write_end(struct address_space = *mapping, struct inode *inode =3D mapping->host; loff_t old_size =3D inode->i_size; bool disksize_changed =3D false; - loff_t new_i_size, zero_len =3D 0; + loff_t new_i_size; handle_t *handle; =20 if (unlikely(!folio_buffers(folio))) { @@ -3240,19 +3237,15 @@ static int ext4_da_do_write_end(struct address_spac= e *mapping, folio_unlock(folio); folio_put(folio); =20 - if (pos > old_size) { + if (pos > old_size) pagecache_isize_extended(inode, old_size, pos); - zero_len =3D pos - old_size; - } =20 - if (!disksize_changed && !zero_len) + if (!disksize_changed) return copied; =20 - handle =3D ext4_journal_start(inode, EXT4_HT_INODE, 2); + handle =3D ext4_journal_start(inode, EXT4_HT_INODE, 1); if (IS_ERR(handle)) return PTR_ERR(handle); - if (zero_len) - ext4_block_zero_eof(inode, old_size, pos); ext4_mark_inode_dirty(handle, inode); ext4_journal_stop(handle); =20 --=20 2.52.0