linux-kernel - Re: [PATCH v2 4/4] mm/vmalloc: Hugepage vmalloc mappings

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Date:   Wed, 1 Jul 2020 15:10:35 +0800
From:   Zefan Li <lizefan@...wei.com>
To:     Nicholas Piggin <npiggin@...il.com>, <linux-mm@...ck.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "Borislav Petkov" <bp@...en8.de>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 4/4] mm/vmalloc: Hugepage vmalloc mappings

>  static void *__vmalloc_node(unsigned long size, unsigned long align,
> -			    gfp_t gfp_mask, pgprot_t prot,
> -			    int node, const void *caller);
> +			gfp_t gfp_mask, pgprot_t prot, unsigned long vm_flags,
> +			int node, const void *caller);
>  static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> -				 pgprot_t prot, int node)
> +				 pgprot_t prot, unsigned int page_shift,
> +				 int node)
>  {
>  	struct page **pages;
> +	unsigned long addr = (unsigned long)area->addr;
> +	unsigned long size = get_vm_area_size(area);
> +	unsigned int page_order = page_shift - PAGE_SHIFT;
>  	unsigned int nr_pages, array_size, i;
>  	const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
>  	const gfp_t alloc_mask = gfp_mask | __GFP_NOWARN;
>  	const gfp_t highmem_mask = (gfp_mask & (GFP_DMA | GFP_DMA32)) ?
> -					0 :
> -					__GFP_HIGHMEM;
> +					0 : __GFP_HIGHMEM;
>  
> -	nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
> +	nr_pages = size >> page_shift;

while try out this patchset, we encountered a BUG_ON in account_kernel_stack()
in kernel/fork.c.

BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);

which obviously should be updated accordingly.

>  	array_size = (nr_pages * sizeof(struct page *));
>  
>  	/* Please note that the recursion is strictly bounded. */
>  	if (array_size > PAGE_SIZE) {
>  		pages = __vmalloc_node(array_size, 1, nested_gfp|highmem_mask,
> -				PAGE_KERNEL, node, area->caller);
> +				PAGE_KERNEL, 0, node, area->caller);
>  	} else {
>  		pages = kmalloc_node(array_size, nested_gfp, node);
>  	}