[PATCH v2] mtd: Fix partition alignment check on multi-erasesize devices

[Boris Brezillon]

On Mon, 25 Sep 2017 10:19:57 +0200
Boris Brezillon <boris.brezillon at free-electrons.com> wrote:

> Commit 1eeef2d7483a ("mtd: handle partitioning on devices with 0
> erasesize") introduced a regression on heterogeneous erase region
> devices. Alignment of the partition was tested against the master
> eraseblock size which can be bigger than the slave one, thus leading
> to some partitions being marked as read-only.
> 
> Update wr_alignment to match this slave erasesize after this erasesize
> has been determined by picking the biggest erasesize of all the regions
> embedded in the MTD partition.
> 
> Reported-by: Mathias Thore <Mathias.Thore at infinera.com>
> Fixes: 1eeef2d7483a ("mtd: handle partitioning on devices with 0 erasesize")
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>

Applied.

> ---
> Changes in v2:
> - Fix build error reported by Mathias
> ---
>  drivers/mtd/mtdpart.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index 5736b0c90b33..a308e707392d 100644
> --- a/drivers/mtd/mtdpart.c
> +++ b/drivers/mtd/mtdpart.c
> @@ -581,6 +581,14 @@ static struct mtd_part *allocate_partition(struct mtd_info *parent,
>  		slave->mtd.erasesize = parent->erasesize;
>  	}
>  
> +	/*
> +	 * Slave erasesize might differ from the master one if the master
> +	 * exposes several regions with different erasesize. Adjust
> +	 * wr_alignment accordingly.
> +	 */
> +	if (!(slave->mtd.flags & MTD_NO_ERASE))
> +		wr_alignment = slave->mtd.erasesize;
> +
>  	tmp = slave->offset;
>  	remainder = do_div(tmp, wr_alignment);
>  	if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {