linux-kernel - Re: [PATCH v4 2/5] mmc: move 'parent' tracking to mmc_blk

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Date:	Wed, 22 Jun 2016 10:03:11 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Bart Van Assche <bart.vanassche@...disk.com>
Cc:	Jens Axboe <axboe@...com>, Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-block@...r.kernel.org, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v4 2/5] mmc: move 'parent' tracking to mmc_blk_data

On Tue, Jun 21, 2016 at 11:38 PM, Bart Van Assche
<bart.vanassche@...disk.com> wrote:
> On 06/21/2016 10:46 PM, Dan Williams wrote:
>>
>> In preparation for the removal of 'driverfs_dev' from 'struct gendisk',
>> carry this data in mmc_blk_data. It is used for registration of parent
>> disks and partitions.
>>
>> Cc: Ulf Hansson <ulf.hansson@...aro.org>
>> Reported-by: Bart Van Assche <bart.vanassche@...disk.com>
>> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>> ---
>>  drivers/mmc/card/block.c |    5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>> index 383184743f9a..d1733424bf6e 100644
>> --- a/drivers/mmc/card/block.c
>> +++ b/drivers/mmc/card/block.c
>> @@ -93,6 +93,7 @@ static DEFINE_SPINLOCK(mmc_blk_lock);
>>   */
>>  struct mmc_blk_data {
>>         spinlock_t      lock;
>> +       struct device   *parent;
>>         struct gendisk  *disk;
>>         struct mmc_queue queue;
>>         struct list_head part;
>> @@ -2270,7 +2271,7 @@ again:
>>         md->disk->fops = &mmc_bdops;
>>         md->disk->private_data = md;
>>         md->disk->queue = md->queue.queue;
>> -       md->disk->driverfs_dev = parent;
>> +       md->parent = parent;
>>         set_disk_ro(md->disk, md->read_only || default_ro);
>>         md->disk->flags = GENHD_FL_EXT_DEVT;
>>         if (area_type & (MMC_BLK_DATA_AREA_RPMB | MMC_BLK_DATA_AREA_BOOT))
>> @@ -2458,7 +2459,7 @@ static int mmc_add_disk(struct mmc_blk_data *md)
>>         int ret;
>>         struct mmc_card *card = md->queue.card;
>>
>> -       add_disk(md->disk);
>> +       device_add_disk(md->parent, md->disk);
>>         md->force_ro.show = force_ro_show;
>>         md->force_ro.store = force_ro_store;
>>         sysfs_attr_init(&md->force_ro.attr);
>
>
> What will the impact be of this patch on code that accesses driverfs_dev
> like printk_all_partitions()? Will this patch hurt bisectability?

Hmm, yes there will be a point in the history where
printk_all_partitions() will print " (driver?)" for mmc devices
instead of " driver: %s".  I would not classify that as breaking
bisection, but it's easy enough to fix up in v5.