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Date:   Thu, 30 Mar 2023 10:29:12 -0700
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Subject: Re: [PATCH v4 4/6] userfaultfd: convert mfill_atomic_hugetlb() to use
 a folio
Content-Language: en-US
To:     Peng Zhang <zhangpeng362@huawei.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        willy@infradead.org, mike.kravetz@oracle.com
Cc:     vishal.moola@gmail.com, muchun.song@linux.dev,
        wangkefeng.wang@huawei.com, sunnanyong@huawei.com
References: <20230330134045.375163-1-zhangpeng362@huawei.com>
 <20230330134045.375163-5-zhangpeng362@huawei.com>
From:   Sidhartha Kumar <sidhartha.kumar@oracle.com>
In-Reply-To: <20230330134045.375163-5-zhangpeng362@huawei.com>
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On 3/30/23 6:40 AM, Peng Zhang wrote:
> From: ZhangPeng <zhangpeng362@huawei.com>
> 
> Convert hugetlb_mfill_atomic_pte() to take in a folio pointer instead of
> a page pointer. Convert mfill_atomic_hugetlb() to use a folio.
> 
> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
> ---
>   include/linux/hugetlb.h |  4 ++--
>   mm/hugetlb.c            | 26 +++++++++++++-------------
>   mm/userfaultfd.c        | 16 ++++++++--------
>   3 files changed, 23 insertions(+), 23 deletions(-)
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 2a758bcd6719..28703fe22386 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -163,7 +163,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
>   			     unsigned long dst_addr,
>   			     unsigned long src_addr,
>   			     uffd_flags_t flags,
> -			     struct page **pagep);
> +			     struct folio **foliop);
>   #endif /* CONFIG_USERFAULTFD */
>   bool hugetlb_reserve_pages(struct inode *inode, long from, long to,
>   						struct vm_area_struct *vma,
> @@ -397,7 +397,7 @@ static inline int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
>   					   unsigned long dst_addr,
>   					   unsigned long src_addr,
>   					   uffd_flags_t flags,
> -					   struct page **pagep)
> +					   struct folio **foliop)
>   {
>   	BUG();
>   	return 0;
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index aade1b513474..c88f856ec2e2 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6178,7 +6178,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
>   			     unsigned long dst_addr,
>   			     unsigned long src_addr,
>   			     uffd_flags_t flags,
> -			     struct page **pagep)
> +			     struct folio **foliop)
>   {
>   	struct mm_struct *dst_mm = dst_vma->vm_mm;
>   	bool is_continue = uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE);
> @@ -6201,8 +6201,8 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
>   		if (IS_ERR(folio))
>   			goto out;
>   		folio_in_pagecache = true;
> -	} else if (!*pagep) {
> -		/* If a page already exists, then it's UFFDIO_COPY for
> +	} else if (!*foliop) {
> +		/* If a folio already exists, then it's UFFDIO_COPY for
>   		 * a non-missing case. Return -EEXIST.
>   		 */
>   		if (vm_shared &&
> @@ -6237,33 +6237,33 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
>   				ret = -ENOMEM;
>   				goto out;
>   			}
> -			*pagep = &folio->page;
> -			/* Set the outparam pagep and return to the caller to
> +			*foliop = folio;
> +			/* Set the outparam foliop and return to the caller to
>   			 * copy the contents outside the lock. Don't free the
> -			 * page.
> +			 * folio.
>   			 */
>   			goto out;
>   		}
>   	} else {
>   		if (vm_shared &&
>   		    hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) {
> -			put_page(*pagep);
> +			folio_put(*foliop);
>   			ret = -EEXIST;
> -			*pagep = NULL;
> +			*foliop = NULL;
>   			goto out;
>   		}
>   
>   		folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0);
>   		if (IS_ERR(folio)) {
> -			put_page(*pagep);
> +			folio_put(*foliop);
>   			ret = -ENOMEM;
> -			*pagep = NULL;
> +			*foliop = NULL;
>   			goto out;
>   		}
> -		copy_user_huge_page(&folio->page, *pagep, dst_addr, dst_vma,
> +		copy_user_huge_page(&folio->page, &(*foliop)->page, dst_addr, dst_vma,
>   				    pages_per_huge_page(h));
> -		put_page(*pagep);
> -		*pagep = NULL;
> +		folio_put(*foliop);
> +		*foliop = NULL;
>   	}
>   
>   	/*
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index b453a4d2a0d3..9e95af5ce2dd 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -322,7 +322,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
>   	pte_t *dst_pte;
>   	unsigned long src_addr, dst_addr;
>   	long copied;
> -	struct page *page;
> +	struct folio *folio;
>   	unsigned long vma_hpagesize;
>   	pgoff_t idx;
>   	u32 hash;
> @@ -342,7 +342,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
>   	src_addr = src_start;
>   	dst_addr = dst_start;
>   	copied = 0;
> -	page = NULL;
> +	folio = NULL;
>   	vma_hpagesize = vma_kernel_pagesize(dst_vma);
>   
>   	/*
> @@ -411,7 +411,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
>   		}
>   
>   		err = hugetlb_mfill_atomic_pte(dst_pte, dst_vma, dst_addr,
> -					       src_addr, flags, &page);
> +					       src_addr, flags, &folio);
>   
>   		hugetlb_vma_unlock_read(dst_vma);
>   		mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> @@ -420,9 +420,9 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
>   
>   		if (unlikely(err == -ENOENT)) {
>   			mmap_read_unlock(dst_mm);
> -			BUG_ON(!page);
> +			BUG_ON(!folio);
>   
> -			err = copy_folio_from_user(page_folio(page),
> +			err = copy_folio_from_user(folio,
>   						   (const void __user *)src_addr, true);
>   			if (unlikely(err)) {
>   				err = -EFAULT;
> @@ -433,7 +433,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
>   			dst_vma = NULL;
>   			goto retry;
>   		} else
> -			BUG_ON(page);
> +			BUG_ON(folio);
>   
>   		if (!err) {
>   			dst_addr += vma_hpagesize;
> @@ -450,8 +450,8 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
>   out_unlock:
>   	mmap_read_unlock(dst_mm);
>   out:
> -	if (page)
> -		put_page(page);
> +	if (folio)
> +		folio_put(folio);
>   	BUG_ON(copied < 0);
>   	BUG_ON(err > 0);
>   	BUG_ON(!copied && !err);
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>