linux-kernel - Re: [PATCH] ubifs: Don't discard nodes in recovery when ecc err detected

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Date:   Sun, 1 Mar 2020 21:46:21 +0100
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     Zhihao Cheng <chengzhihao1@...wei.com>
Cc:     Richard Weinberger <richard@....at>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        "zhangyi (F)" <yi.zhang@...wei.com>, linux-mtd@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ubifs: Don't discard nodes in recovery when ecc err detected

Zhihao Cheng,

On Fri, Feb 21, 2020 at 2:57 PM Zhihao Cheng <chengzhihao1@...wei.com> wrote:
>
> The following process will lead TNC to find no corresponding inode node
> (Reproduce method see Link):

Please help me to understand what exactly is going on.

>   1. Garbage collection.
>      1) move valid inode nodes from leb A to leb B
>         (The leb number of B has been written as GC type bud node in log)
>      2) unmap leb A, and corresponding peb is erased
>         (GCed inode nodes exist only on leb B)

At this point all valid nodes are written to LEB B, right?

>   2. Poweroff. A node near the end of the LEB is corrupted before power
>      on, which is uncorrectable error of ECC.

If writing nodes to B has finished, these pages should be stable.
How can a power-cut affect the pages where these valid nodes sit?

-- 
Thanks,
//richard