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From: =?gb18030?B?uuzJ1bXEzf67r7H9?= <glqhw@qq.com>
To: =?gb18030?B?bGludXgtZjJmcy1kZXZlbA==?=
	<linux-f2fs-devel@lists.sourceforge.net>
Subject: [f2fs-dev]  Potential data corruption?
Date: Sat, 7 Dec 2019 18:10:47 +0800	[thread overview]
Message-ID: <tencent_0B38BD6C2739091DE8A052D6D772D1DEAA06@qq.com> (raw)

Hi F2FS experts,
The following confuses me:

A typical fsync() goes like this:
1) Issue data block IOs
2) Wait for completion
3) Issue chained node block IOs
4) Wait for completion
5) Issue flush command

In order to preserve data consistency under sudden power failure, it requires that the storage device persists data blocks prior to node blocks.
Otherwise, under sudden power failure, it's possible that the persisted node block points to NULL data blocks.

However, according to this study (https://www.usenix.org/conference/fast18/presentation/won), the persistent order of requests doesn't necessarily equals to the request finish order (due to device volatile caches). This means that its possible that the node blocks get persisted prior to data blocks.

Does F2FS have other mechanisms to prevent such inconsistency? Or does it require the device to persist data without reordering?

Thanks!

Hongwei
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             reply	other threads:[~2019-12-07 10:11 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-07 10:10 =?gb18030?B?uuzJ1bXEzf67r7H9?= [this message]
2019-12-08  4:00 ` [f2fs-dev] Potential data corruption? Chao Yu
2019-12-08 13:15   ` Hongwei Qin
2019-12-08 13:41     ` Chao Yu
2019-12-08 13:51     ` Gao Xiang via Linux-f2fs-devel
2019-12-09 10:46       ` Chao Yu

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