Re: [RFC PATCH v1 30/57] drivers/base: Remove PAGE_SIZE compile-time constant assumption

Ryan Roberts
2024-10-16T14:56:04Z

+ Greg Kroah-Hartman

This was a rather tricky series to get the recipients correct for and my script
did not realize that "supporter" was a pseudonym for "maintainer" so you were
missed off the original post. Appologies!

More context in cover letter:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/

On 14/10/2024 11:58, Ryan Roberts wrote:
> To prepare for supporting boot-time page size selection, refactor code
> to remove assumptions about PAGE_SIZE being compile-time constant. Code
> intended to be equivalent when compile-time page size is active.
>
> Update BUILD_BUG_ON() to test against page size limits.
>
> CPUMAP_FILE_MAX_BYTES and CPULIST_FILE_MAX_BYTES are both defined
> relative to PAGE_SIZE, so when these values are assigned to global
> variables via BIN_ATTR_RO(), let's wrap them with
> DEFINE_GLOBAL_PAGE_SIZE_VAR() so that their assignment can be deferred
> until boot-time.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
>
> ***NOTE***
> Any confused maintainers may want to read the cover note here for context:
> https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/
>
> drivers/base/node.c | 6 +++---
> drivers/base/topology.c | 32 ++++++++++++++++----------------
> include/linux/cpumask.h | 5 +++++
> 3 files changed, 24 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index eb72580288e62..30e6549e4c438 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -45,7 +45,7 @@ static inline ssize_t cpumap_read(struct file *file, struct kobject *kobj,
> return n;
> }
>
> -static BIN_ATTR_RO(cpumap, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(cpumap, CPUMAP_FILE_MAX_BYTES);
>
> static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj,
> struct bin_attribute *attr, char *buf,
> @@ -66,7 +66,7 @@ static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj,
> return n;
> }
>
> -static BIN_ATTR_RO(cpulist, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(cpulist, CPULIST_FILE_MAX_BYTES);
>
> /**
> * struct node_access_nodes - Access class device to hold user visible
> @@ -558,7 +558,7 @@ static ssize_t node_read_distance(struct device *dev,
> * buf is currently PAGE_SIZE in length and each node needs 4 chars
> * at the most (distance + space or newline).
> */
> - BUILD_BUG_ON(MAX_NUMNODES * 4 > PAGE_SIZE);
> + BUILD_BUG_ON(MAX_NUMNODES * 4 > PAGE_SIZE_MIN);
>
> for_each_online_node(i) {
> len += sysfs_emit_at(buf, len, "%s%d",
> diff --git a/drivers/base/topology.c b/drivers/base/topology.c
> index 89f98be5c5b99..bdbdbefd95b15 100644
> --- a/drivers/base/topology.c
> +++ b/drivers/base/topology.c
> @@ -62,47 +62,47 @@ define_id_show_func(ppin, "0x%llx");
> static DEVICE_ATTR_ADMIN_RO(ppin);
>
> define_siblings_read_func(thread_siblings, sibling_cpumask);
> -static BIN_ATTR_RO(thread_siblings, CPUMAP_FILE_MAX_BYTES);
> -static BIN_ATTR_RO(thread_siblings_list, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(thread_siblings, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(thread_siblings_list, CPULIST_FILE_MAX_BYTES);
>
> define_siblings_read_func(core_cpus, sibling_cpumask);
> -static BIN_ATTR_RO(core_cpus, CPUMAP_FILE_MAX_BYTES);
> -static BIN_ATTR_RO(core_cpus_list, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(core_cpus, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(core_cpus_list, CPULIST_FILE_MAX_BYTES);
>
> define_siblings_read_func(core_siblings, core_cpumask);
> -static BIN_ATTR_RO(core_siblings, CPUMAP_FILE_MAX_BYTES);
> -static BIN_ATTR_RO(core_siblings_list, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(core_siblings, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(core_siblings_list, CPULIST_FILE_MAX_BYTES);
>
> #ifdef TOPOLOGY_CLUSTER_SYSFS
> define_siblings_read_func(cluster_cpus, cluster_cpumask);
> -static BIN_ATTR_RO(cluster_cpus, CPUMAP_FILE_MAX_BYTES);
> -static BIN_ATTR_RO(cluster_cpus_list, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(cluster_cpus, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(cluster_cpus_list, CPULIST_FILE_MAX_BYTES);
> #endif
>
> #ifdef TOPOLOGY_DIE_SYSFS
> define_siblings_read_func(die_cpus, die_cpumask);
> -static BIN_ATTR_RO(die_cpus, CPUMAP_FILE_MAX_BYTES);
> -static BIN_ATTR_RO(die_cpus_list, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(die_cpus, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(die_cpus_list, CPULIST_FILE_MAX_BYTES);
> #endif
>
> define_siblings_read_func(package_cpus, core_cpumask);
> -static BIN_ATTR_RO(package_cpus, CPUMAP_FILE_MAX_BYTES);
> -static BIN_ATTR_RO(package_cpus_list, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(package_cpus, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(package_cpus_list, CPULIST_FILE_MAX_BYTES);
>
> #ifdef TOPOLOGY_BOOK_SYSFS
> define_id_show_func(book_id, "%d");
> static DEVICE_ATTR_RO(book_id);
> define_siblings_read_func(book_siblings, book_cpumask);
> -static BIN_ATTR_RO(book_siblings, CPUMAP_FILE_MAX_BYTES);
> -static BIN_ATTR_RO(book_siblings_list, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(book_siblings, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(book_siblings_list, CPULIST_FILE_MAX_BYTES);
> #endif
>
> #ifdef TOPOLOGY_DRAWER_SYSFS
> define_id_show_func(drawer_id, "%d");
> static DEVICE_ATTR_RO(drawer_id);
> define_siblings_read_func(drawer_siblings, drawer_cpumask);
> -static BIN_ATTR_RO(drawer_siblings, CPUMAP_FILE_MAX_BYTES);
> -static BIN_ATTR_RO(drawer_siblings_list, CPULIST_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(drawer_siblings, CPUMAP_FILE_MAX_BYTES);
> +static CPU_FILE_BIN_ATTR_RO(drawer_siblings_list, CPULIST_FILE_MAX_BYTES);
> #endif
>
> static struct bin_attribute *bin_attrs[] = {
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index 53158de44b837..f654b4198abc2 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -1292,4 +1292,9 @@ cpumap_print_list_to_buf(char *buf, const struct cpumask *mask,
> ? (NR_CPUS * 9)/32 - 1 : PAGE_SIZE)
> #define CPULIST_FILE_MAX_BYTES (((NR_CPUS * 7)/2 > PAGE_SIZE) ? (NR_CPUS * 7)/2 : PAGE_SIZE)
>
> +#define CPU_FILE_BIN_ATTR_RO(_name, _size) \
> + DEFINE_GLOBAL_PAGE_SIZE_VAR(struct bin_attribute, \
> + bin_attr_##_name, \
> + __BIN_ATTR_RO(_name, _size))
> +
> #endif /* __LINUX_CPUMASK_H */