Re: [PATCH v5 07/14] mm: shmem: allow THP support determination at folio allocation time

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 5/29/26 10:55 PM, Luiz Capitulino wrote:
> In order to enable THP support in shmem today, besides the user
> configuration required, the CPU must support PMD-sized pages. This
> is the case because of the following has_transparent_hugepage()
> usage:
> 
> - shmem_parse_one() and shmem_parse_huge(): Check if THP is built-in and
>    if the CPU supports PMD-sized pages
> 
> - shmem_init(): Since the CONFIG_TRANSPARENT_HUGEPAGE guard is outside
>    the code block calling has_transparent_hugepage(), the
>    has_transparent_hugepage() call is exclusively checking if the CPU
>    supports PMD-sized pages
> 
> While it's necessary to check if CONFIG_TRANSPARENT_HUGEPAGE is enabled
> in all cases, shmem can determine THP size support at folio allocation
> time. Therefore, drop the has_transparent_hugepage() usage listed above
> while keeping the CONFIG_TRANSPARENT_HUGEPAGE checks.
> 
> Additionally, we need to check if PMD size order is supported in
> shmem_getattr(). Use pgtable_has_pmd_leaves() for that.
> 
> Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
> ---
>   mm/shmem.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 88bc0c292f1a..108dc969b92a 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -689,7 +689,7 @@ static int shmem_parse_huge(const char *str)
>   	else
>   		return -EINVAL;
>   
> -	if (!has_transparent_hugepage() &&
> +	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
>   	    huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
>   		return -EINVAL;
>   
> @@ -1303,6 +1303,8 @@ static int shmem_getattr(struct mnt_idmap *idmap,
>   	generic_fillattr(idmap, request_mask, inode, stat);
>   
>   	orders = shmem_huge_global_enabled(inode, 0, 0, false, NULL, 0);
> +	if (!pgtable_has_pmd_leaves())
> +		orders &= ~BIT(PMD_ORDER);

Ah, you did in this patch, but this change should belong in patch 14?