From mboxrd@z Thu Jan 1 00:00:00 1970 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 9DD8F2C21DC; Thu, 27 Nov 2025 06:13:09 +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=1764223993; cv=none; b=jZZKXGjdezhV6HMaywm5k0AQZzBDYnzd232+FRn+GnPFvBn8ZiUZ4Cch4CofFk26NaaMmuGSG5s86R/UtMJdBW+Adj/eWrPeqygmzhV5B48/IcMNEYe8OIZ4uDysn16L2VHCh25yc8hxm2Y+KKKuoH0jI5s8JippghOe9M+iwmc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764223993; c=relaxed/simple; bh=FbD8NOpvlKse2tL4sG2H1TmszWMrqtxg0iJSSiD1vao=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KSsYYsWa4vvEkccukJCI3yTqvX19wgTagkhMisKhGi9lLiRt9ihXwgWg1iVWR+ZeaBg9BzUoSQvJEM6KhbZO6QHxB/Q8hC3aRTvF/dPDwQ/MN/wxoVki8SKlO6c5kR6uht9bL1zcdRsA5EqqNqHifygsleFK9aQGE9PJlrQrsAE= 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 [172.19.93.142]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4dH5gL1VWHzYQv3c; Thu, 27 Nov 2025 14:12:14 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id 5070F1A07BB; Thu, 27 Nov 2025 14:13:07 +0800 (CST) Received: from [10.174.178.152] (unknown [10.174.178.152]) by APP2 (Coremail) with SMTP id Syh0CgBnD3bx6ydpPaKsCA--.42133S3; Thu, 27 Nov 2025 14:13:07 +0800 (CST) Message-ID: Date: Thu, 27 Nov 2025 14:13:05 +0800 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 03/13] ext4: don't zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1 To: Ojaswin Mujoo Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz, yi.zhang@huawei.com, yizhang089@gmail.com, libaokun1@huawei.com, yangerkun@huawei.com References: <20251121060811.1685783-1-yi.zhang@huaweicloud.com> <20251121060811.1685783-4-yi.zhang@huaweicloud.com> Content-Language: en-US From: Zhang Yi In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:Syh0CgBnD3bx6ydpPaKsCA--.42133S3 X-Coremail-Antispam: 1UD129KBjvJXoWxGFWUZF4UWryrKw4DKw4rKrg_yoW5Kr17pF Wfua4UKr4kt340934IqF1qvr1q9w4FgrW7CrW5G3Z8KasFg342gFs7Gw4jqFyFgr48ZF1U Ar4Fyr98G3Z8Aa7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUv0b4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUGVWUXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS 14v26r1q6r43MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I 8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8 ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x 0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_ Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7IUb mii3UUUUU== X-CM-SenderInfo: d1lo6xhdqjqx5xdzvxpfor3voofrz/ On 11/26/2025 7:29 PM, Ojaswin Mujoo wrote: > On Fri, Nov 21, 2025 at 02:08:01PM +0800, Zhang Yi wrote: >> From: Zhang Yi >> >> When allocating initialized blocks from a large unwritten extent, or >> when splitting an unwritten extent during end I/O and converting it to >> initialized, there is currently a potential issue of stale data if the >> extent needs to be split in the middle. >> >> 0 A B N >> [UUUUUUUUUUUU] U: unwritten extent >> [--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_ENTIRE_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 mark the entire extent from 0 to N >> as written. >> >> 0 A B N >> [WWWWWWWWWWWW] W: written extent >> [SSDDDDDDDDZZ] Z: zeroed, S: stale 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 left >> a stale written extent from 0 to A. >> >> 0 A B N >> [WW|WWWWWWWWWW] >> [SS|DDDDDDDDZZ] >> >> Fix this by pass EXT4_EXT_DATA_PARTIAL_VALID1 to ext4_split_extent_at() >> when splitting at B, don't convert the entire extent to written and left >> it as unwritten after zeroing out B to N. The remaining work is just >> like the standard two-part split. ext4_split_extent() will pass the >> EXT4_EXT_DATA_VALID2 flag when it calls ext4_split_extent_at() for the >> second time, allowing it to properly handle the split. If the split is >> successful, it will keep extent from 0 to A as unwritten. >> >> Signed-off-by: Zhang Yi > > Hi Yi, > > This patch looks good to me. I'm just wondering since this is a stale > data exposure that might need a backport, should we add a Fixes: tag > and also keep these fixes before the refactor in 1/13 so backport is > easier. Sure, I can move patch 01 after all the fix patches. Thanks, Yi. > > Other than that, feel free to add: > Reviewed-by: Ojaswin Mujoo > > Regards, > ojaswin > >> --- >> fs/ext4/extents.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c >> index f7aa497e5d6c..cafe66cb562f 100644 >> --- a/fs/ext4/extents.c >> +++ b/fs/ext4/extents.c >> @@ -3294,6 +3294,13 @@ static struct ext4_ext_path *ext4_split_extent_at(handle_t *handle, >> err = ext4_ext_zeroout(inode, &zero_ex); >> if (err) >> goto fix_extent_len; >> + /* >> + * The first half contains partially valid data, the splitting >> + * of this extent has not been completed, fix extent length >> + * and ext4_split_extent() split will the first half again. >> + */ >> + if (split_flag & EXT4_EXT_DATA_PARTIAL_VALID1) >> + goto fix_extent_len; >> >> /* update the extent length and mark as initialized */ >> ex->ee_len = cpu_to_le16(ee_len); >> @@ -3364,7 +3371,9 @@ static struct ext4_ext_path *ext4_split_extent(handle_t *handle, >> split_flag1 |= EXT4_EXT_MARK_UNWRIT1 | >> EXT4_EXT_MARK_UNWRIT2; >> if (split_flag & EXT4_EXT_DATA_VALID2) >> - split_flag1 |= EXT4_EXT_DATA_ENTIRE_VALID1; >> + split_flag1 |= map->m_lblk > ee_block ? >> + EXT4_EXT_DATA_PARTIAL_VALID1 : >> + EXT4_EXT_DATA_ENTIRE_VALID1; >> path = ext4_split_extent_at(handle, inode, path, >> map->m_lblk + map->m_len, split_flag1, flags1); >> if (IS_ERR(path)) >> -- >> 2.46.1 >>