[PATCH] block: fix block device detection

[Ahmad Fatoum]

On 7/24/25 11:13, Marco Felsch wrote:
> Before commit a6410cfa9aff ("block: mark underlying cdev with
> DEVFS_IS_BLOCK_DEV") the block device decision was made based on the
> block_ops. Since each parition-cdev inherits the parent (master)
> cdev-ops the parition-cdevs were detected as block device.
> 
> Commit a6410cfa9aff the detection mechanism to be based on cdev flag but
> commit a6410cfa9aff forgot to pass the flag to the partition (child)
> cdev.
> 
> Fix this by passing the DEVFS_IS_BLOCK_DEV to the partition (child) cdev
> as well. Add a small helper function to query the inheritable devfs
> flags instead of open coding it within __devfs_add_partition().
> 
> Fixes: a6410cfa9aff ("block: mark underlying cdev with DEVFS_IS_BLOCK_DEV")

Reviewed-by: Ahmad Fatoum <a.fatoum at pengutronix.de>

> Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
> ---
>  fs/devfs-core.c  |  4 ++--
>  include/driver.h | 10 ++++++++++
>  2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/devfs-core.c b/fs/devfs-core.c
> index 73a13be7336d..f80281aaf91c 100644
> --- a/fs/devfs-core.c
> +++ b/fs/devfs-core.c
> @@ -584,7 +584,7 @@ static struct cdev *__devfs_add_partition(struct cdev *cdev,
>  	loff_t _end = end ? *end : 0;
>  	static struct cdev *new;
>  	struct cdev *overlap;
> -	unsigned inherited_flags = 0;
> +	unsigned inherited_flags;
>  
>  	if (cdev_by_name(partinfo->name))
>  		return ERR_PTR(-EEXIST);
> @@ -628,7 +628,7 @@ static struct cdev *__devfs_add_partition(struct cdev *cdev,
>  	}
>  
>  	/* Filter flags that we want to pass along to children */
> -	inherited_flags |= cdev->flags & DEVFS_WRITE_AUTOERASE;
> +	inherited_flags = get_inheritable_devfs_flags(cdev);
>  
>  	if (IS_ENABLED(CONFIG_MTD) && cdev->mtd) {
>  		struct mtd_info *mtd;
> diff --git a/include/driver.h b/include/driver.h
> index dd50a7aa3cce..01e04578540b 100644
> --- a/include/driver.h
> +++ b/include/driver.h
> @@ -627,6 +627,16 @@ static inline bool cdev_is_gpt_partitioned(const struct cdev *master)
>  	return master && (master->flags & DEVFS_IS_GPT_PARTITIONED);
>  }
>  
> +#define DEVFS_INHERITABLE_FLAGS (DEVFS_WRITE_AUTOERASE | DEVFS_IS_BLOCK_DEV)
> +
> +static inline unsigned int
> +get_inheritable_devfs_flags(const struct cdev *parent_cdev)
> +{
> +	if (!parent_cdev)
> +		return 0;
> +	return parent_cdev->flags & DEVFS_INHERITABLE_FLAGS;
> +}
> +
>  struct cdev *
>  cdev_find_child_by_gpt_typeuuid(struct cdev *cdev, const guid_t *typeuuid);
>  

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