Re: [PATCH] mm/memory_hotplug: fix memmap_on_memory sysfs value retrieval

David Hildenbrand
2024-01-10T16:15:44Z

On 10.01.24 15:01, Sumanth Korikkar wrote:
> The set_memmap_mode() function stores the kernel parameter memmap mode
> as an integer. However, the get_memmap_mode() function utilizes
> param_get_bool() to fetch the value as a boolean, leading to potential
> endianness issue. On Big-endian architectures, the memmap_on_memory is
> consistently displayed as 'N' regardless of its actual status.
>
> To address this endianness problem, the solution involves obtaining the
> mode as an integer. This adjustment ensures the proper display of the
> memmap_on_memory parameter, presenting it as one of the following
> options: Force, Y, or N.
>
> Fixes: 2d1f649c7c08 ("mm/memory_hotplug: support memmap_on_memory when memmap is not aligned to pageblocks")
> Suggested-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
> Cc: <stable@vger.kernel.org> # v6.6+
> Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
> ---
> mm/memory_hotplug.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index b944e8bf1911..707027f69150 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -101,9 +101,11 @@ static int set_memmap_mode(const char *val, const struct kernel_param *kp)
>
> static int get_memmap_mode(char *buffer, const struct kernel_param *kp)
> {
> - if (*((int *)kp->arg) == MEMMAP_ON_MEMORY_FORCE)
> - return sprintf(buffer, "force\n");
> - return param_get_bool(buffer, kp);
> + int mode = *((int *)kp->arg);
> +
> + if (mode == MEMMAP_ON_MEMORY_FORCE)
> + return sprintf(buffer, "force\n");
> + return sprintf(buffer, "%c\n", mode ? 'Y' : 'N');
> }

I was wondering if we want to return "Y" instead of "force". But using
force seems more consistent.

Acked-by: David Hildenbrand <david@redhat.com>

--
Cheers,

David / dhildenb