linux-kernel - Re: [PATCH v2 2/9] mm/huge_memory: move more common code into insert

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Message-ID: <872b3bb6-7ea1-4a60-9436-b98d3c3231a4@lucifer.local>
Date: Thu, 17 Jul 2025 16:42:35 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        xen-devel@...ts.xenproject.org, linux-fsdevel@...r.kernel.org,
        nvdimm@...ts.linux.dev, Andrew Morton <akpm@...ux-foundation.org>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
        Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
        Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
        Hugh Dickins <hughd@...gle.com>, Oscar Salvador <osalvador@...e.de>,
        Lance Yang <lance.yang@...ux.dev>,
        Alistair Popple <apopple@...dia.com>
Subject: Re: [PATCH v2 2/9] mm/huge_memory: move more common code into
 insert_pud()

On Thu, Jul 17, 2025 at 01:52:05PM +0200, David Hildenbrand wrote:
> Let's clean it all further up.
>
> No functional change intended.
>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>
> Reviewed-by: Alistair Popple <apopple@...dia.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>

LGTM:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  mm/huge_memory.c | 36 +++++++++++++-----------------------
>  1 file changed, 13 insertions(+), 23 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 1178760d2eda4..849feacaf8064 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1518,25 +1518,30 @@ static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
>  	return pud;
>  }
>
> -static void insert_pud(struct vm_area_struct *vma, unsigned long addr,
> +static vm_fault_t insert_pud(struct vm_area_struct *vma, unsigned long addr,
>  		pud_t *pud, struct folio_or_pfn fop, pgprot_t prot, bool write)
>  {
>  	struct mm_struct *mm = vma->vm_mm;
> +	spinlock_t *ptl;
>  	pud_t entry;
>
> +	if (addr < vma->vm_start || addr >= vma->vm_end)
> +		return VM_FAULT_SIGBUS;
> +
> +	ptl = pud_lock(mm, pud);
>  	if (!pud_none(*pud)) {
>  		const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) :
>  					  fop.pfn;
>
>  		if (write) {
>  			if (WARN_ON_ONCE(pud_pfn(*pud) != pfn))
> -				return;
> +				goto out_unlock;
>  			entry = pud_mkyoung(*pud);
>  			entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
>  			if (pudp_set_access_flags(vma, addr, pud, entry, 1))
>  				update_mmu_cache_pud(vma, addr, pud);
>  		}
> -		return;
> +		goto out_unlock;
>  	}
>
>  	if (fop.is_folio) {
> @@ -1555,6 +1560,9 @@ static void insert_pud(struct vm_area_struct *vma, unsigned long addr,
>  	}
>  	set_pud_at(mm, addr, pud, entry);
>  	update_mmu_cache_pud(vma, addr, pud);
> +out_unlock:
> +	spin_unlock(ptl);
> +	return VM_FAULT_NOPAGE;
>  }
>
>  /**
> @@ -1576,7 +1584,6 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, unsigned long pfn,
>  	struct folio_or_pfn fop = {
>  		.pfn = pfn,
>  	};
> -	spinlock_t *ptl;
>
>  	/*
>  	 * If we had pud_special, we could avoid all these restrictions,
> @@ -1588,16 +1595,9 @@ vm_fault_t vmf_insert_pfn_pud(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;
> -
>  	pfnmap_setup_cachemode_pfn(pfn, &pgprot);
>
> -	ptl = pud_lock(vma->vm_mm, vmf->pud);
> -	insert_pud(vma, addr, vmf->pud, fop, pgprot, write);
> -	spin_unlock(ptl);
> -
> -	return VM_FAULT_NOPAGE;
> +	return insert_pud(vma, addr, vmf->pud, fop, pgprot, write);
>  }
>  EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
>
> @@ -1614,25 +1614,15 @@ vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio,
>  {
>  	struct vm_area_struct *vma = vmf->vma;
>  	unsigned long addr = vmf->address & PUD_MASK;
> -	pud_t *pud = vmf->pud;
> -	struct mm_struct *mm = vma->vm_mm;
>  	struct folio_or_pfn fop = {
>  		.folio = folio,
>  		.is_folio = true,
>  	};
> -	spinlock_t *ptl;
> -
> -	if (addr < vma->vm_start || addr >= vma->vm_end)
> -		return VM_FAULT_SIGBUS;
>
>  	if (WARN_ON_ONCE(folio_order(folio) != PUD_ORDER))
>  		return VM_FAULT_SIGBUS;
>
> -	ptl = pud_lock(mm, pud);
> -	insert_pud(vma, addr, vmf->pud, fop, vma->vm_page_prot, write);
> -	spin_unlock(ptl);
> -
> -	return VM_FAULT_NOPAGE;
> +	return insert_pud(vma, addr, vmf->pud, fop, vma->vm_page_prot, write);
>  }
>  EXPORT_SYMBOL_GPL(vmf_insert_folio_pud);
>  #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
> --
> 2.50.1
>