linux-kernel - Re: [PATCH v4 3/4] mtd: core: protect access to MTD devices while in suspend

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Date:   Mon, 1 Nov 2021 08:40:59 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Sean Nyekjaer <sean@...nix.com>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/4] mtd: core: protect access to MTD devices while
 in suspend

On Tue, 26 Oct 2021 07:55:50 +0200
Sean Nyekjaer <sean@...nix.com> wrote:

> @@ -1406,6 +1423,7 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
>  		    const u_char *buf)
>  {
>  	struct mtd_info *master = mtd_get_master(mtd);
> +	int ret;
>  
>  	*retlen = 0;
>  	if (!master->_panic_write)
> @@ -1419,8 +1437,12 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
>  	if (!master->oops_panic_write)
>  		master->oops_panic_write = true;
>  
> -	return master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
> -				    retlen, buf);
> +	mtd_start_access(master);
> +	ret = master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
> +				   retlen, buf);
> +	mtd_end_access(master);
> +
> +	return ret;
>  }

I suspect panic_write should be an exception, otherwise a panic in the
suspend path would never be able to write its data to the flash.