linux-kernel - Re: [PATCH 1/1] ubifs: Try to recover from missing znode

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Message-ID: <351bdd98-98ac-036f-4685-56e88a102cf3@huawei.com>
Date: Wed, 9 Oct 2024 18:46:43 +0800
From: Zhihao Cheng <chengzhihao1@...wei.com>
To: Richard Weinberger <richard@....at>
CC: Benedikt Spranger <b.spranger@...utronix.de>, linux-kernel
	<linux-kernel@...r.kernel.org>, linux-mtd <linux-mtd@...ts.infradead.org>
Subject: Re: [PATCH 1/1] ubifs: Try to recover from missing znode

在 2024/10/9 14:03, Richard Weinberger 写道:
> ----- Ursprüngliche Mail -----
>> Von: "chengzhihao1" <chengzhihao1@...wei.com>
>> An: "Benedikt Spranger" <b.spranger@...utronix.de>, "linux-kernel" <linux-kernel@...r.kernel.org>
>> CC: "linux-mtd" <linux-mtd@...ts.infradead.org>, "richard" <richard@....at>
>> Gesendet: Mittwoch, 9. Oktober 2024 04:23:02
>> Betreff: Re: [PATCH 1/1] ubifs: Try to recover from missing znode
> 
>> 在 2024/10/8 21:33, Benedikt Spranger 写道:
>>> After powercut on a system using ubifs mounting failed:
>>>
>>> 2024-09-30T12:38:26.880487+02:00 sonja kernel: UBIFS error (ubi0:0 pid 2178):
>>> ubifs_read_node [ubifs]: bad node type (255 but expected 9)
>>> 2024-09-30T12:38:26.880506+02:00 sonja kernel: UBIFS error (ubi0:0 pid 2178):
>>> ubifs_read_node [ubifs]: bad node at LEB 103:46920, LEB mapping status 0
>>> 2024-09-30T12:38:26.880509+02:00 sonja kernel: Not a node, first 24 bytes:
>>> 2024-09-30T12:38:26.880510+02:00 sonja kernel: 00000000: ff ff ff ff ff ff ff ff
>>> ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>> ........................
>>>
>>> While traversing over zbranches during the journal replay one zbranch
>>> points to a znode, which was not written to the flash and therefore the
>>> flash is empty.
>>
>> UBIFS guarantees two things for znodes:
>> 1) all index nodes(in commit seq N) are written on flash before master
>> nodes(for commit seq N) are written.
>> 2) all index nodes(in commit seq N) won't be erased from flash before
>> master nodes(for commit seq N+1) are written.
>> So, I don't understand that why znodes not exist during journal replaying?
> 
> In addition to that, is just one znode missing or are larger parts of the flash
> empty?
> 

After reviewing the TNC related code, I cannot find out any illegal 
behaviors to make znode lost or valid index LEB erased.

Hi Benedikt, could you provide a corrupted UBIFS image? Let me try 
getting more information.