[PATCH] block: genhd: Add disk/partition specific uevent callbacks for partition info

[PATCH] block: genhd: Add disk/partition specific uevent callbacks for partition info

[John Stultz]

From: San Mehat <san@google.com>

This patch has been carried in the Android tree for quite some
time and is one of the few patches required to get a mainline
kernel up and running with an exsiting Android userspace. So I
wanted to submit it for review and consideration if it should
be merged.

For disk devices, a new uevent parameter 'NPARTS' specifies the number
of partitions detected by the kernel. Partition devices get 'PARTN' which
specifies the partitions index in the table, and 'PARTNAME', which
specifies PARTNAME specifices the partition name of a partition device

Android's userspace uses this for creating device node links from the
partition name and number: ie:
	/dev/block/platform/soc/by-name/system
or
	/dev/block/platform/soc/by-num/p1

One can see its usage here:
https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#355
and
https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#494

Thoughts and feedback would be greatly appreciated!

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Rom Lemarchand <romlem@google.com>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Dima Zavin <dima@android.com>
[jstultz: Added more context to commit message & whitespace fix]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 block/genhd.c             | 17 +++++++++++++++++
 block/partition-generic.c | 11 +++++++++++
 2 files changed, 28 insertions(+)

diff --git a/block/genhd.c b/block/genhd.c
index 0c706f3..248139e 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1115,6 +1115,22 @@ static void disk_release(struct device *dev)
 		blk_put_queue(disk->queue);
 	kfree(disk);
 }
+
+static int disk_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	struct disk_part_iter piter;
+	struct hd_struct *part;
+	int cnt = 0;
+
+	disk_part_iter_init(&piter, disk, 0);
+	while ((part = disk_part_iter_next(&piter)))
+		cnt++;
+	disk_part_iter_exit(&piter);
+	add_uevent_var(env, "NPARTS=%u", cnt);
+	return 0;
+}
+
 struct class block_class = {
 	.name		= "block",
 };
@@ -1134,6 +1150,7 @@ static struct device_type disk_type = {
 	.groups		= disk_attr_groups,
 	.release	= disk_release,
 	.devnode	= block_devnode,
+	.uevent		= disk_uevent,
 };
 
 #ifdef CONFIG_PROC_FS
diff --git a/block/partition-generic.c b/block/partition-generic.c
index e771113..e5d91c9 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -216,10 +216,21 @@ static void part_release(struct device *dev)
 	kfree(p);
 }
 
+static int part_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct hd_struct *part = dev_to_part(dev);
+
+	add_uevent_var(env, "PARTN=%u", part->partno);
+	if (part->info && part->info->volname[0])
+		add_uevent_var(env, "PARTNAME=%s", part->info->volname);
+	return 0;
+}
+
 struct device_type part_type = {
 	.name		= "partition",
 	.groups		= part_attr_groups,
 	.release	= part_release,
+	.uevent		= part_uevent,
 };
 
 static void delete_partition_rcu_cb(struct rcu_head *head)
-- 
1.9.1

Re: [PATCH] block: genhd: Add disk/partition specific uevent callbacks for partition info

[John Stultz]

On Thu, Oct 22, 2015 at 10:27 AM, John Stultz <john.stultz@linaro.org> wrote:
> From: San Mehat <san@google.com>
>
> This patch has been carried in the Android tree for quite some
> time and is one of the few patches required to get a mainline
> kernel up and running with an exsiting Android userspace. So I
> wanted to submit it for review and consideration if it should
> be merged.
>
> For disk devices, a new uevent parameter 'NPARTS' specifies the number
> of partitions detected by the kernel. Partition devices get 'PARTN' which
> specifies the partitions index in the table, and 'PARTNAME', which
> specifies PARTNAME specifices the partition name of a partition device
>
> Android's userspace uses this for creating device node links from the
> partition name and number: ie:
>         /dev/block/platform/soc/by-name/system
> or
>         /dev/block/platform/soc/by-num/p1
>
> One can see its usage here:
> https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#355
> and
> https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#494
>
> Thoughts and feedback would be greatly appreciated!

Ping? Any thoughts or objections to this?

thanks
-john

Re: [PATCH] block: genhd: Add disk/partition specific uevent callbacks for partition info

[Jeff Moyer]

Hi John,

John Stultz <john.stultz@linaro.org> writes:

> From: San Mehat <san@google.com>
>
> This patch has been carried in the Android tree for quite some
> time and is one of the few patches required to get a mainline
> kernel up and running with an exsiting Android userspace. So I
> wanted to submit it for review and consideration if it should
> be merged.
>
> For disk devices, a new uevent parameter 'NPARTS' specifies the number
> of partitions detected by the kernel. Partition devices get 'PARTN' which
> specifies the partitions index in the table, and 'PARTNAME', which
> specifies PARTNAME specifices the partition name of a partition device
>
> Android's userspace uses this for creating device node links from the
> partition name and number: ie:
> 	/dev/block/platform/soc/by-name/system
> or
> 	/dev/block/platform/soc/by-num/p1
>
> One can see its usage here:
> https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#355
> and
> https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#494

Those links don't appear to use the NPARTS uevent parameter, unless I
missed it.

> Thoughts and feedback would be greatly appreciated!

I can't say I have strong feelings one way or the other.  I've CC'd Kay
and Harald, hoping they might have an opinion.

Cheers,
Jeff

>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Rom Lemarchand <romlem@google.com>
> Cc: Android Kernel Team <kernel-team@android.com>
> Signed-off-by: Dima Zavin <dima@android.com>
> [jstultz: Added more context to commit message & whitespace fix]
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
>  block/genhd.c             | 17 +++++++++++++++++
>  block/partition-generic.c | 11 +++++++++++
>  2 files changed, 28 insertions(+)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 0c706f3..248139e 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -1115,6 +1115,22 @@ static void disk_release(struct device *dev)
>  		blk_put_queue(disk->queue);
>  	kfree(disk);
>  }
> +
> +static int disk_uevent(struct device *dev, struct kobj_uevent_env *env)
> +{
> +	struct gendisk *disk = dev_to_disk(dev);
> +	struct disk_part_iter piter;
> +	struct hd_struct *part;
> +	int cnt = 0;
> +
> +	disk_part_iter_init(&piter, disk, 0);
> +	while ((part = disk_part_iter_next(&piter)))
> +		cnt++;
> +	disk_part_iter_exit(&piter);
> +	add_uevent_var(env, "NPARTS=%u", cnt);
> +	return 0;
> +}
> +
>  struct class block_class = {
>  	.name		= "block",
>  };
> @@ -1134,6 +1150,7 @@ static struct device_type disk_type = {
>  	.groups		= disk_attr_groups,
>  	.release	= disk_release,
>  	.devnode	= block_devnode,
> +	.uevent		= disk_uevent,
>  };
>  
>  #ifdef CONFIG_PROC_FS
> diff --git a/block/partition-generic.c b/block/partition-generic.c
> index e771113..e5d91c9 100644
> --- a/block/partition-generic.c
> +++ b/block/partition-generic.c
> @@ -216,10 +216,21 @@ static void part_release(struct device *dev)
>  	kfree(p);
>  }
>  
> +static int part_uevent(struct device *dev, struct kobj_uevent_env *env)
> +{
> +	struct hd_struct *part = dev_to_part(dev);
> +
> +	add_uevent_var(env, "PARTN=%u", part->partno);
> +	if (part->info && part->info->volname[0])
> +		add_uevent_var(env, "PARTNAME=%s", part->info->volname);
> +	return 0;
> +}
> +
>  struct device_type part_type = {
>  	.name		= "partition",
>  	.groups		= part_attr_groups,
>  	.release	= part_release,
> +	.uevent		= part_uevent,
>  };
>  
>  static void delete_partition_rcu_cb(struct rcu_head *head)

Re: [PATCH] block: genhd: Add disk/partition specific uevent callbacks for partition info

[John Stultz]

On Mon, Nov 2, 2015 at 10:03 AM, Jeff Moyer <jmoyer@redhat.com> wrote:
> Hi John,
>
> John Stultz <john.stultz@linaro.org> writes:
>
>> From: San Mehat <san@google.com>
>>
>> This patch has been carried in the Android tree for quite some
>> time and is one of the few patches required to get a mainline
>> kernel up and running with an exsiting Android userspace. So I
>> wanted to submit it for review and consideration if it should
>> be merged.
>>
>> For disk devices, a new uevent parameter 'NPARTS' specifies the number
>> of partitions detected by the kernel. Partition devices get 'PARTN' which
>> specifies the partitions index in the table, and 'PARTNAME', which
>> specifies PARTNAME specifices the partition name of a partition device
>>
>> Android's userspace uses this for creating device node links from the
>> partition name and number: ie:
>>       /dev/block/platform/soc/by-name/system
>> or
>>       /dev/block/platform/soc/by-num/p1
>>
>> One can see its usage here:
>> https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#355
>> and
>> https://android.googlesource.com/platform/system/core/+/master/init/devices.cpp#494
>
> Those links don't appear to use the NPARTS uevent parameter, unless I
> missed it.

So good point! It looks like with Android Marshmallow they dropped using NPARTS.
For context, here is where it was used with Lollipop:
   http://androidxref.com/5.1.1_r6/xref/system/vold/DirectVolume.cpp#192

Unless Rom or someone on the Android team objects, I'll remove that
chunk from the patch and re-submit.

Thanks for the review!
-john