Re: [PATCH 12/18] common: partitions: record whether disk is GPT or MBR partitioned

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 01.06.23 10:19, Marco Felsch wrote:
> On 23-06-01, Ahmad Fatoum wrote:
>> On 31.05.23 19:33, Marco Felsch wrote:
>>> On 23-05-31, Ahmad Fatoum wrote:
>>>> Currently, the only way to differentiate between a GPT disk and a MBR
>>>> one is to check whether the cdev's device has a guid (=> GPT) or a
>>>> nt_signature (=> MBR) device parameter. We already have a flag parameter
>>>> though, so let's record this info there for easy retrieval.
>>>>
>>>> We intentionally don't use the struct cdev::filetype member, because
>>>> we don't want to change behavior of file_detect_type().
>>>>
>>>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>>>> ---
>>>>  common/partitions/dos.c |  2 ++
>>>>  common/partitions/efi.c |  2 ++
>>>>  fs/fs.c                 |  4 ++++
>>>>  include/driver.h        | 20 +++++++++++++++++---
>>>>  4 files changed, 25 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/common/partitions/dos.c b/common/partitions/dos.c
>>>> index ad60c0b27b46..7472824b00b9 100644
>>>> --- a/common/partitions/dos.c
>>>> +++ b/common/partitions/dos.c
>>>> @@ -185,6 +185,8 @@ static void dos_partition(void *buf, struct block_device *blk,
>>>>  	if (signature)
>>>>  		sprintf(blk->cdev.diskuuid, "%08x", signature);
>>>>  
>>>> +	blk->cdev.flags |= DEVFS_IS_MBR_PARTITIONED;
>>>> +
>>>>  	table = (struct partition_entry *)&buffer[446];
>>>>  
>>>>  	for (i = 0; i < 4; i++) {
>>>> diff --git a/common/partitions/efi.c b/common/partitions/efi.c
>>>> index 780a8695e8a8..df63b82afe24 100644
>>>> --- a/common/partitions/efi.c
>>>> +++ b/common/partitions/efi.c
>>>> @@ -449,6 +449,8 @@ static void efi_partition(void *buf, struct block_device *blk,
>>>>  	snprintf(blk->cdev.diskuuid, sizeof(blk->cdev.diskuuid), "%pUl", &gpt->disk_guid);
>>>>  	dev_add_param_string_fixed(blk->dev, "guid", blk->cdev.diskuuid);
>>>>  
>>>> +	blk->cdev.flags |= DEVFS_IS_GPT_PARTITIONED;
>>>> +
>>>>  	nb_part = le32_to_cpu(gpt->num_partition_entries);
>>>>  
>>>>  	if (nb_part > MAX_PARTITION) {
>>>> diff --git a/fs/fs.c b/fs/fs.c
>>>> index 9d8aab268ca4..2d2d327c5fbc 100644
>>>> --- a/fs/fs.c
>>>> +++ b/fs/fs.c
>>>> @@ -94,6 +94,10 @@ void cdev_print(const struct cdev *cdev)
>>>>  			printf(" table-partition");
>>>>  		if (cdev->flags & DEVFS_IS_MCI_MAIN_PART_DEV)
>>>>  			printf(" mci-main-partition");
>>>> +		if (cdev->flags & DEVFS_IS_GPT_PARTITIONED)
>>>> +			printf(" gpt-partitioned");
>>>> +		if (cdev->flags & DEVFS_IS_MBR_PARTITIONED)
>>>> +			printf(" mbr-partitioned");
>>>>  		if (cdev->mtd)
>>>>  			printf(" mtd");
>>>>  		printf(" )");
>>>> diff --git a/include/driver.h b/include/driver.h
>>>> index 118d2adb6750..5f2eae65466f 100644
>>>> --- a/include/driver.h
>>>> +++ b/include/driver.h
>>>> @@ -584,9 +584,23 @@ extern struct list_head cdev_list;
>>>>  #define DEVFS_PARTITION_FIXED		(1U << 0)
>>>>  #define DEVFS_PARTITION_READONLY	(1U << 1)
>>>>  #define DEVFS_IS_CHARACTER_DEV		(1U << 3)
>>>> -#define DEVFS_IS_MCI_MAIN_PART_DEV	(1U << 4)
>>>> -#define DEVFS_PARTITION_FROM_OF		(1U << 5)
>>>> -#define DEVFS_PARTITION_FROM_TABLE	(1U << 6)
>>>> +#define DEVFS_PARTITION_FROM_OF		(1U << 4)
>>>> +#define DEVFS_PARTITION_FROM_TABLE	(1U << 5)
>>>> +#define DEVFS_IS_GPT_PARTITIONED	(1U << 6)
>>>> +#define DEVFS_IS_MBR_PARTITIONED	(1U << 7)
>>>> +#define DEVFS_IS_MCI_MAIN_PART_DEV	(1U << 8)
>>>
>>> Why do you reorder the bits here again?
>>
>> I wanted the partition bits to be together.
>>
>>>> +
>>>> +static inline bool cdev_is_gpt_partitioned(const struct cdev *master)
>>>> +{
>>>> +	return master && (master->flags & DEVFS_IS_GPT_PARTITIONED)
>>>> +		== DEVFS_IS_GPT_PARTITIONED;
>>>
>>> Why not just: 'return !!(master->flags & DEVFS_IS_GPT_PARTITIONED)' ?
>>
>> Left over from when this was more than one bit. I will change to:
>>
>>   return master && (master->flags & DEVFS_IS_GPT_PARTITIONED)
>>
>> I want to keep the NULL check, as we only set this for the master device.
> 
> By 'as we only set this for the master device' you mean the flags right?
> We don't expect the 'struct cdev*' parameter to be NULL.

stat has this use:

  if (cdev_is_mbr_partitioned(cdev->master))
        nbytes += printf("DOS parttype: 0x%02x\t", cdev->dos_partition_type);

The same line is called for all cdevs and disks are handled gracefully
by cdev->master being NULL and cdev_is_mbr_partitioned having a NULL
check.

> 
> Regards,
>   Marco
> 
>>
>> Cheers,
>> Ahmad
>>
>>
>>>
>>> Regards,
>>>   Marco
>>>
>>>> +}
>>>> +
>>>> +static inline bool cdev_is_mbr_partitioned(const struct cdev *master)
>>>> +{
>>>> +	return master && (master->flags & DEVFS_IS_MBR_PARTITIONED)
>>>> +		== DEVFS_IS_MBR_PARTITIONED;
>>>> +}
>>>>  
>>>>  struct cdev *devfs_add_partition(const char *devname, loff_t offset,
>>>>  		loff_t size, unsigned int flags, const char *name);
>>>> -- 
>>>> 2.39.2
>>>>
>>>>
>>>>
>>>
>>
>> -- 
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>>
>>
> 

-- 
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