Re: [PATCH v3 01/11] mm/huge_memory: move more common code into insert_pmd()

[Lance Yang <lance.yang@linux.dev>]

On 2025/8/11 19:26, David Hildenbrand wrote:
> Let's clean it all further up.
> 
> No functional change intended.
> 
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> Reviewed-by: Alistair Popple <apopple@nvidia.com>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Nice. Feel free to add:

Reviewed-by: Lance Yang <lance.yang@linux.dev>

Thanks,
Lance

> ---
>   mm/huge_memory.c | 72 ++++++++++++++++--------------------------------
>   1 file changed, 24 insertions(+), 48 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 2b4ea5a2ce7d2..5314a89d676f1 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1379,15 +1379,25 @@ struct folio_or_pfn {
>   	bool is_folio;
>   };
>   
> -static int insert_pmd(struct vm_area_struct *vma, unsigned long addr,
> +static vm_fault_t insert_pmd(struct vm_area_struct *vma, unsigned long addr,
>   		pmd_t *pmd, struct folio_or_pfn fop, pgprot_t prot,
> -		bool write, pgtable_t pgtable)
> +		bool write)
>   {
>   	struct mm_struct *mm = vma->vm_mm;
> +	pgtable_t pgtable = NULL;
> +	spinlock_t *ptl;
>   	pmd_t entry;
>   
> -	lockdep_assert_held(pmd_lockptr(mm, pmd));
> +	if (addr < vma->vm_start || addr >= vma->vm_end)
> +		return VM_FAULT_SIGBUS;
>   
> +	if (arch_needs_pgtable_deposit()) {
> +		pgtable = pte_alloc_one(vma->vm_mm);
> +		if (!pgtable)
> +			return VM_FAULT_OOM;
> +	}
> +
> +	ptl = pmd_lock(mm, pmd);
>   	if (!pmd_none(*pmd)) {
>   		const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) :
>   					  fop.pfn;
> @@ -1395,15 +1405,14 @@ static int insert_pmd(struct vm_area_struct *vma, unsigned long addr,
>   		if (write) {
>   			if (pmd_pfn(*pmd) != pfn) {
>   				WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
> -				return -EEXIST;
> +				goto out_unlock;
>   			}
>   			entry = pmd_mkyoung(*pmd);
>   			entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
>   			if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
>   				update_mmu_cache_pmd(vma, addr, pmd);
>   		}
> -
> -		return -EEXIST;
> +		goto out_unlock;
>   	}
>   
>   	if (fop.is_folio) {
> @@ -1424,11 +1433,17 @@ static int insert_pmd(struct vm_area_struct *vma, unsigned long addr,
>   	if (pgtable) {
>   		pgtable_trans_huge_deposit(mm, pmd, pgtable);
>   		mm_inc_nr_ptes(mm);
> +		pgtable = NULL;
>   	}
>   
>   	set_pmd_at(mm, addr, pmd, entry);
>   	update_mmu_cache_pmd(vma, addr, pmd);
> -	return 0;
> +
> +out_unlock:
> +	spin_unlock(ptl);
> +	if (pgtable)
> +		pte_free(mm, pgtable);
> +	return VM_FAULT_NOPAGE;
>   }
>   
>   /**
> @@ -1450,9 +1465,6 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, unsigned long pfn,
>   	struct folio_or_pfn fop = {
>   		.pfn = pfn,
>   	};
> -	pgtable_t pgtable = NULL;
> -	spinlock_t *ptl;
> -	int error;
>   
>   	/*
>   	 * If we had pmd_special, we could avoid all these restrictions,
> @@ -1464,25 +1476,9 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, unsigned long pfn,
>   						(VM_PFNMAP|VM_MIXEDMAP));
>   	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
>   
> -	if (addr < vma->vm_start || addr >= vma->vm_end)
> -		return VM_FAULT_SIGBUS;
> -
> -	if (arch_needs_pgtable_deposit()) {
> -		pgtable = pte_alloc_one(vma->vm_mm);
> -		if (!pgtable)
> -			return VM_FAULT_OOM;
> -	}
> -
>   	pfnmap_setup_cachemode_pfn(pfn, &pgprot);
>   
> -	ptl = pmd_lock(vma->vm_mm, vmf->pmd);
> -	error = insert_pmd(vma, addr, vmf->pmd, fop, pgprot, write,
> -			   pgtable);
> -	spin_unlock(ptl);
> -	if (error && pgtable)
> -		pte_free(vma->vm_mm, pgtable);
> -
> -	return VM_FAULT_NOPAGE;
> +	return insert_pmd(vma, addr, vmf->pmd, fop, pgprot, write);
>   }
>   EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
>   
> @@ -1491,35 +1487,15 @@ vm_fault_t vmf_insert_folio_pmd(struct vm_fault *vmf, struct folio *folio,
>   {
>   	struct vm_area_struct *vma = vmf->vma;
>   	unsigned long addr = vmf->address & PMD_MASK;
> -	struct mm_struct *mm = vma->vm_mm;
>   	struct folio_or_pfn fop = {
>   		.folio = folio,
>   		.is_folio = true,
>   	};
> -	spinlock_t *ptl;
> -	pgtable_t pgtable = NULL;
> -	int error;
> -
> -	if (addr < vma->vm_start || addr >= vma->vm_end)
> -		return VM_FAULT_SIGBUS;
>   
>   	if (WARN_ON_ONCE(folio_order(folio) != PMD_ORDER))
>   		return VM_FAULT_SIGBUS;
>   
> -	if (arch_needs_pgtable_deposit()) {
> -		pgtable = pte_alloc_one(vma->vm_mm);
> -		if (!pgtable)
> -			return VM_FAULT_OOM;
> -	}
> -
> -	ptl = pmd_lock(mm, vmf->pmd);
> -	error = insert_pmd(vma, addr, vmf->pmd, fop, vma->vm_page_prot,
> -			   write, pgtable);
> -	spin_unlock(ptl);
> -	if (error && pgtable)
> -		pte_free(mm, pgtable);
> -
> -	return VM_FAULT_NOPAGE;
> +	return insert_pmd(vma, addr, vmf->pmd, fop, vma->vm_page_prot, write);
>   }
>   EXPORT_SYMBOL_GPL(vmf_insert_folio_pmd);
>