Re: [v1 5/6] mm: move allocation of gigantic hstates to the start of mm_core_init

[Mike Rapoport <rppt@kernel.org>]

On Thu, Jul 27, 2023 at 09:46:23PM +0100, Usama Arif wrote:
> Whether the initialization of tail struct pages of a hugepage
> happens or not will become dependent on the commandline
> parameter hugetlb_free_vmemmap in the future. Hence,
> hugetlb_hstate_alloc_pages needs to be after command line parameters
> are parsed and the start of mm_core_init is a good point.
> 
> Signed-off-by: Usama Arif <usama.arif@bytedance.com>
> ---
>  include/linux/hugetlb.h |  1 +
>  mm/hugetlb.c            | 18 ++++++++++--------
>  mm/mm_init.c            |  4 ++++
>  3 files changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index ca3c8e10f24a..2b20553deef3 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -1271,4 +1271,5 @@ hugetlb_walk(struct vm_area_struct *vma, unsigned long addr, unsigned long sz)
>  	return huge_pte_offset(vma->vm_mm, addr, sz);
>  }
>  
> +void __init hugetlb_hstate_alloc_gigantic_pages(void);

this should be in mm/internal.h with a static inline stub for !CONFIG_HUGETLBFS

>  #endif /* _LINUX_HUGETLB_H */
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 58cf5978bee1..c1fcf2af591a 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4418,14 +4418,6 @@ static int __init hugepages_setup(char *s)
>  		}
>  	}
>  
> -	/*
> -	 * Global state is always initialized later in hugetlb_init.
> -	 * But we need to allocate gigantic hstates here early to still
> -	 * use the bootmem allocator.
> -	 */
> -	if (hugetlb_max_hstate && hstate_is_gigantic(parsed_hstate))
> -		hugetlb_hstate_alloc_pages(parsed_hstate);
> -
>  	last_mhp = mhp;
>  
>  	return 1;
> @@ -4437,6 +4429,16 @@ static int __init hugepages_setup(char *s)
>  }
>  __setup("hugepages=", hugepages_setup);
>  
> +void __init hugetlb_hstate_alloc_gigantic_pages(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < HUGE_MAX_HSTATE; i++) {
> +		if (hstate_is_gigantic(&hstates[i]))
> +			hugetlb_hstate_alloc_pages(&hstates[i]);
> +	}
> +}
> +
>  /*
>   * hugepagesz command line processing
>   * A specific huge page size can only be specified once with hugepagesz.
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index a1963c3322af..5585c66c3c42 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -26,6 +26,7 @@
>  #include <linux/pgtable.h>
>  #include <linux/swap.h>
>  #include <linux/cma.h>
> +#include <linux/hugetlb.h>
>  #include "internal.h"
>  #include "slab.h"
>  #include "shuffle.h"
> @@ -2768,6 +2769,9 @@ static void __init mem_init_print_info(void)
>   */
>  void __init mm_core_init(void)
>  {
> +#ifdef CONFIG_HUGETLBFS
> +	hugetlb_hstate_alloc_gigantic_pages();
> +#endif

Please add a comment why it should be called here.

>  	/* Initializations relying on SMP setup */
>  	build_all_zonelists(NULL);
>  	page_alloc_init_cpuhp();
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.