From nobody Tue Dec 2 01:54:22 2025 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 C8C5F1C8FBA; Fri, 21 Nov 2025 06:10:28 +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=1763705432; cv=none; b=qe5xIfJG3j3SV9+PBnvUmmfQ/f5UTSvTymVmpEOE8iQog/lJTfuvUVgEj5vMqPduOlklLNrDEhdFuNwUxVMVRVLYNQ/VwT97FZmqLYOlzhrO4CUDuL+fmypwxkqQwkTV9EUO96G+wvSao4OVvG9/QnWg1/G5Gi1hIeNXegJPFjo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763705432; c=relaxed/simple; bh=zi3AN8i8AXlP66f3R7EElNkmkBR6iT++xtTay90h6ao=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QxEFG/SPYib9CivRYGmifTQVvg8yPkub49BbQ8J5+YRUcnMfNHmlUlAZBhb2Wo+1ZVOUDEftF6bqYtiqKfnKOoYlNCG7UiORw/4MbPVwLgJFtGnLmFgQYyThX9c6XcWlEKm+WIgjXhUgMc4FYKsNhsGN0JT3iXFXJg4ZlSqYAuQ= 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 [172.19.163.235]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4dCPvC45PyzYQv44; Fri, 21 Nov 2025 14:09:43 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id 9AC9C1A0D66; 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--.63807S8; 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 04/13] ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O Date: Fri, 21 Nov 2025 14:08:02 +0800 Message-ID: <20251121060811.1685783-5-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--.63807S8 X-Coremail-Antispam: 1UD129KBjvJXoWxGF1fJFyftw17XF17Kr4xXrb_yoW5KFW8pF 4I9F1xJr4vy34ru34xJ3Wqqr17uw18GrsrAryYg3yUKayDtrySgF1Fka4rWFyFgr4rZayY yrWFva4Ykas8G37anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUmI14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkE bVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67 AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI 42IY6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCw CI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnI WIevJa73UjIFyTuYvjfUOyIUUUUUU X-CM-SenderInfo: d1lo6xhdqjqx5xdzvxpfor3voofrz/ Content-Type: text/plain; charset="utf-8" From: Zhang Yi When allocating blocks during within-EOF DIO and writeback with dioread_nolock enabled, EXT4_GET_BLOCKS_PRE_IO was set to split an existing large unwritten extent. However, EXT4_GET_BLOCKS_CONVERT was set when calling ext4_split_convert_extents(), which may potentially result in stale data issues. Assume we have an unwritten extent, and then DIO writes the second half. [UUUUUUUUUUUUUUUU] on-disk extent U: unwritten extent [UUUUUUUUUUUUUUUU] extent status tree |<- ->| ----> dio write this range First, ext4_iomap_alloc() call ext4_map_blocks() with EXT4_GET_BLOCKS_PRE_IO, EXT4_GET_BLOCKS_UNWRIT_EXT and EXT4_GET_BLOCKS_CREATE flags set. ext4_map_blocks() find this extent and call ext4_split_convert_extents() with EXT4_GET_BLOCKS_CONVERT and the above flags set. Then, ext4_split_convert_extents() calls ext4_split_extent() with EXT4_EXT_MAY_ZEROOUT, EXT4_EXT_MARK_UNWRIT2 and EXT4_EXT_DATA_VALID2 flags set, and it calls ext4_split_extent_at() to split the second half with EXT4_EXT_DATA_VALID2, EXT4_EXT_MARK_UNWRIT1, EXT4_EXT_MAY_ZEROOUT and EXT4_EXT_MARK_UNWRIT2 flags set. However, ext4_split_extent_at() failed to insert extent since a temporary lack -ENOSPC. It zeroes out the first half but convert the entire on-disk extent to written since the EXT4_EXT_DATA_VALID2 flag set, but left the second half as unwritten in the extent status tree. [0000000000SSSSSS] data S: stale data, 0: zeroed [WWWWWWWWWWWWWWWW] on-disk extent W: written extent [WWWWWWWWWWUUUUUU] extent status tree Finally, if the DIO failed to write data to the disk, the stale data in the second half will be exposed once the cached extent entry is gone. Fix this issue by not passing EXT4_GET_BLOCKS_CONVERT when splitting an unwritten extent before submitting I/O, and make ext4_split_convert_extents() to zero out the entire extent range to zero for this case, and also mark the extent in the extent status tree for consistency. Signed-off-by: Zhang Yi Reviewed-by: Ojaswin Mujoo --- fs/ext4/extents.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index cafe66cb562f..2db84f6b0056 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3733,11 +3733,15 @@ static struct ext4_ext_path *ext4_split_convert_ext= ents(handle_t *handle, /* Convert to unwritten */ if (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN) { split_flag |=3D EXT4_EXT_DATA_ENTIRE_VALID1; - /* Convert to initialized */ - } else if (flags & EXT4_GET_BLOCKS_CONVERT) { + /* Split the existing unwritten extent */ + } else if (flags & (EXT4_GET_BLOCKS_UNWRIT_EXT | + EXT4_GET_BLOCKS_CONVERT)) { split_flag |=3D ee_block + ee_len <=3D eof_block ? EXT4_EXT_MAY_ZEROOUT : 0; - split_flag |=3D (EXT4_EXT_MARK_UNWRIT2 | EXT4_EXT_DATA_VALID2); + split_flag |=3D EXT4_EXT_MARK_UNWRIT2; + /* Convert to initialized */ + if (flags & EXT4_GET_BLOCKS_CONVERT) + split_flag |=3D EXT4_EXT_DATA_VALID2; } flags |=3D EXT4_GET_BLOCKS_PRE_IO; return ext4_split_extent(handle, inode, path, map, split_flag, flags, @@ -3913,7 +3917,7 @@ ext4_ext_handle_unwritten_extents(handle_t *handle, s= truct inode *inode, /* get_block() before submitting IO, split the extent */ if (flags & EXT4_GET_BLOCKS_PRE_IO) { path =3D ext4_split_convert_extents(handle, inode, map, path, - flags | EXT4_GET_BLOCKS_CONVERT, allocated); + flags, allocated); if (IS_ERR(path)) return path; /* --=20 2.46.1