[4.2.y-ckt stable] Patch "mmc: block: Use the mmc host device index as the mmcblk device index" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

On Mon, Apr 25, 2016 at 02:36:12PM -0700, Peter Hurley wrote:
> Hi Kamal,
> 
> On 04/25/2016 12:44 PM, Kamal Mostafa wrote:
> > This is a note to let you know that I have just added a patch titled
> > 
> >     mmc: block: Use the mmc host device index as the mmcblk device index
> > 
> > to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
> > which can be found at:
> > 
> >     http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue
> > 
> > This patch is scheduled to be released in version 4.2.8-ckt9.
> 
> The commit that triggers this stable fix was first avail on 4.5
> so shouldn't be necessary for 4.2.y

Thanks Peter.  Dropping this from the 4.2-stable queue.

> [unless commit 520bd7a8b415
> ("mmc: core: Optimize boot time by detecting cards simultaneously"
> was backported?]

(It wasn't.)

 -Kamal

> 
> Regards,
> Peter Hurley
> 
> 
> 
> > If you, or anyone else, feels it should not be added to this tree, please 
> > reply to this email.
> > 
> > For more information about the 4.2.y-ckt tree, see
> > https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
> > 
> > Thanks.
> > -Kamal
> > 
> > ---8<------------------------------------------------------------
> > 
> > From 0be97d0b4a5695ebc2872064effcae0cd58e9baf Mon Sep 17 00:00:00 2001
> > From: Ulf Hansson <ulf.hansson at linaro.org>
> > Date: Wed, 6 Apr 2016 16:12:08 +0200
> > Subject: mmc: block: Use the mmc host device index as the mmcblk device index
> > 
> > commit 9aaf3437aa72ed5370bf32c99580a3fa2c330e3d upstream.
> > 
> > Commit 520bd7a8b415 ("mmc: core: Optimize boot time by detecting cards
> > simultaneously") causes regressions for some platforms.
> > 
> > These platforms relies on fixed mmcblk device indexes, instead of
> > deploying the defacto standard with UUID/PARTUUID. In other words their
> > rootfs needs to be available at hardcoded paths, like /dev/mmcblk0p2.
> > 
> > Such guarantees have never been made by the kernel, but clearly the above
> > commit changes the behaviour. More precisely, because of that the order
> > changes of how cards becomes detected, so do their corresponding mmcblk
> > device indexes.
> > 
> > As the above commit significantly improves boot time for some platforms
> > (magnitude of seconds), let's avoid reverting this change but instead
> > restore the behaviour of how mmcblk device indexes becomes picked.
> > 
> > By using the same index for the mmcblk device as for the corresponding mmc
> > host device, the probe order of mmc host devices decides the index we get
> > for the mmcblk device.
> > 
> > For those platforms that suffers from a regression, one could expect that
> > this updated behaviour should be sufficient to meet their expectations of
> > "fixed" mmcblk device indexes.
> > 
> > Another side effect from this change, is that the same index is used for
> > the mmc host device, the mmcblk device and the mmc block queue. That
> > should clarify their relationship.
> > 
> > Reported-by: Peter Hurley <peter at hurleysoftware.com>
> > Reported-by: Laszlo Fiat <laszlo.fiat at gmail.com>
> > Cc: Linus Torvalds <torvalds at linux-foundation.org>
> > Fixes: 520bd7a8b415 ("mmc: core: Optimize boot time by detecting cards
> > simultaneously")
> > Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
> > Signed-off-by: Kamal Mostafa <kamal at canonical.com>
> > ---
> >  drivers/mmc/card/block.c | 18 +-----------------
> >  1 file changed, 1 insertion(+), 17 deletions(-)
> > 
> > diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> > index 88c4e08..449937e 100644
> > --- a/drivers/mmc/card/block.c
> > +++ b/drivers/mmc/card/block.c
> > @@ -86,7 +86,6 @@ static int max_devices;
> > 
> >  /* TODO: Replace these with struct ida */
> >  static DECLARE_BITMAP(dev_use, MAX_DEVICES);
> > -static DECLARE_BITMAP(name_use, MAX_DEVICES);
> > 
> >  /*
> >   * There is one mmc_blk_data per slot.
> > @@ -105,7 +104,6 @@ struct mmc_blk_data {
> >  	unsigned int	usage;
> >  	unsigned int	read_only;
> >  	unsigned int	part_type;
> > -	unsigned int	name_idx;
> >  	unsigned int	reset_done;
> >  #define MMC_BLK_READ		BIT(0)
> >  #define MMC_BLK_WRITE		BIT(1)
> > @@ -2109,19 +2107,6 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
> >  		goto out;
> >  	}
> > 
> > -	/*
> > -	 * !subname implies we are creating main mmc_blk_data that will be
> > -	 * associated with mmc_card with dev_set_drvdata. Due to device
> > -	 * partitions, devidx will not coincide with a per-physical card
> > -	 * index anymore so we keep track of a name index.
> > -	 */
> > -	if (!subname) {
> > -		md->name_idx = find_first_zero_bit(name_use, max_devices);
> > -		__set_bit(md->name_idx, name_use);
> > -	} else
> > -		md->name_idx = ((struct mmc_blk_data *)
> > -				dev_to_disk(parent)->private_data)->name_idx;
> > -
> >  	md->area_type = area_type;
> > 
> >  	/*
> > @@ -2170,7 +2155,7 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
> >  	 */
> > 
> >  	snprintf(md->disk->disk_name, sizeof(md->disk->disk_name),
> > -		 "mmcblk%u%s", md->name_idx, subname ? subname : "");
> > +		 "mmcblk%u%s", card->host->index, subname ? subname : "");
> > 
> >  	if (mmc_card_mmc(card))
> >  		blk_queue_logical_block_size(md->queue.queue,
> > @@ -2324,7 +2309,6 @@ static void mmc_blk_remove_parts(struct mmc_card *card,
> >  	struct list_head *pos, *q;
> >  	struct mmc_blk_data *part_md;
> > 
> > -	__clear_bit(md->name_idx, name_use);
> >  	list_for_each_safe(pos, q, &md->part) {
> >  		part_md = list_entry(pos, struct mmc_blk_data, part);
> >  		list_del(pos);
> > --
> > 2.7.4
> > 
>