Re: [PATCH v2] mtd: rework partitions handling

From: Boris Brezillon <bbrezillon@kernel.org>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Tudor Ambarus <Tudor.Ambarus@microchip.com>,
	Richard Weinberger <richard@nod.at>,
	Marek Vasut <marek.vasut@gmail.com>,
	linux-mtd@lists.infradead.org,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v2] mtd: rework partitions handling
Date: Mon, 21 Jan 2019 09:51:20 +0100	[thread overview]
Message-ID: <20190121095120.5d7850cb@bbrezillon> (raw)
In-Reply-To: <20190116162144.4458-1-miquel.raynal@bootlin.com>

On Wed, 16 Jan 2019 17:21:44 +0100
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> @@ -457,13 +525,31 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs);
>  
>  static inline int mtd_suspend(struct mtd_info *mtd)
>  {
> -	return mtd->_suspend ? mtd->_suspend(mtd) : 0;
> +	struct mtd_info *master = mtd_get_master(mtd);
> +	int ret;
> +
> +	if (master->suspended)
> +		return 0;
> +
> +	ret = master->_suspend ? master->_suspend(master) : 0;
> +	if (ret)
> +		return ret;
> +
> +	master->suspended = 1;

It's not entirely clear to me whether dev->suspend() hooks can be
called simultaneously on several CPUs or not, if that's the case, we
should use an atomic_t for the ->suspended field and use the
atomic_add_unless() function when manipulating it.

	if (!atomic_add_unless(&master->suspended, 1, 1))
		return 0;

	ret = master->_suspend ? master->_suspend(master) : 0;
	if (ret) {
		atomic_dec(&master->suspended);
		return ret;
	}

> +	return 0;
>  }
>  
>  static inline void mtd_resume(struct mtd_info *mtd)
>  {
> -	if (mtd->_resume)
> -		mtd->_resume(mtd);
> +	struct mtd_info *master = mtd_get_master(mtd);
> +
> +	if (!master->suspended)
> +		return;
> +
> +	if (master->_resume)
> +		master->_resume(master);
> +
> +	master->suspended = 0;

Same here:

	if (!atomic_add_unless(&master->suspended, -1, 0))
		return;

	if (master->_resume)
		master->_resume(master);
>  }

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