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

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Message-ID: <883601802.30668.1728453832223.JavaMail.zimbra@nod.at>
Date: Wed, 9 Oct 2024 08:03:52 +0200 (CEST)
From: Richard Weinberger <richard@....at>
To: chengzhihao1 <chengzhihao1@...wei.com>
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

----- 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?

Thanks,
//richard