linux-kernel - Re: [PATCH] mtd: set mtd partition panic write flag

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Message-ID: <1718371158.75883.1572995022606.JavaMail.zimbra@nod.at>
Date:   Wed, 6 Nov 2019 00:03:42 +0100 (CET)
From:   Richard Weinberger <richard@....at>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Kamal Dasu <kdasu.kdev@...il.com>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Vignesh Raghavendra <vigneshr@...com>
Subject: Re: [PATCH] mtd: set mtd partition panic write flag

----- Ursprüngliche Mail -----
> Von: "Miquel Raynal" <miquel.raynal@...tlin.com>
> An: "Kamal Dasu" <kdasu.kdev@...il.com>
> CC: "linux-mtd" <linux-mtd@...ts.infradead.org>, "bcm-kernel-feedback-list" <bcm-kernel-feedback-list@...adcom.com>,
> "linux-kernel" <linux-kernel@...r.kernel.org>, "David Woodhouse" <dwmw2@...radead.org>, "Brian Norris"
> <computersforpeace@...il.com>, "Marek Vasut" <marek.vasut@...il.com>, "richard" <richard@....at>, "Vignesh Raghavendra"
> <vigneshr@...com>
> Gesendet: Dienstag, 5. November 2019 20:03:44
> Betreff: Re: [PATCH] mtd: set mtd partition panic write flag

> Hi Kamal,
> 
> Richard, something to look into below :)

I'm still recovering from a bad cold. So my brain is not fully working ;)
 
> Kamal Dasu <kdasu.kdev@...il.com> wrote on Mon, 21 Oct 2019 15:32:52
> -0400:
> 
>> Check mtd panic write flag and set the mtd partition panic
>> write flag so that low level drivers can use it to take
>> required action to ensure oops data gets written to assigned
>> mtd partition.
> 
> I feel there is something wrong with the current implementation
> regarding partitions but I am not sure this is the right fix. Is this
> something you detected with some kind of static checker or did you
> actually experience an issue?
> 
> In the commit log you say "check mtd (I suppose you mean the
> master) panic write flag and set the mtd partition panic write flag"
> which makes sense, but in reality my understanding is that you do the
> opposite: you check mtd->oops_panic_write which is the partitions'
> structure, and set part->parent->oops_panic_write which is the master's
> flag.

IIUC the problem happens when you run mtdoops on a mtd partition.
The the flag is only set for the partition instead for the master.

So the right fix would be setting the parent's oops_panic_write in
mtd_panic_write().
Then we don't have to touch mtdpart.c

Thanks,
//richard