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Date:   Fri, 9 Aug 2019 17:06:57 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     <ira.weiny@...el.com>, Andrew Morton <akpm@...ux-foundation.org>
CC:     Jason Gunthorpe <jgg@...pe.ca>,
        Dan Williams <dan.j.williams@...el.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Theodore Ts'o <tytso@....edu>, Michal Hocko <mhocko@...e.com>,
        Dave Chinner <david@...morbit.com>,
        <linux-xfs@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-nvdimm@...ts.01.org>, <linux-ext4@...r.kernel.org>,
        <linux-mm@...ck.org>
Subject: Re: [RFC PATCH v2 10/19] mm/gup: Pass a NULL vaddr_pin through GUP
 fast

On 8/9/19 3:58 PM, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
> 
> Internally GUP fast needs to know that fast users will not support file
> pins.  Pass NULL for vaddr_pin through the fast call stack so that the
> pin code can return an error if it encounters file backed memory within
> the address range.
> 

Reviewed-by: John Hubbard <jhubbard@...dia.com>

thanks,
-- 
John Hubbard
NVIDIA

> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> ---
>  mm/gup.c | 65 ++++++++++++++++++++++++++++++++++----------------------
>  1 file changed, 40 insertions(+), 25 deletions(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index 7a449500f0a6..504af3e9a942 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1813,7 +1813,8 @@ static inline struct page *try_get_compound_head(struct page *page, int refs)
>  
>  #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
>  static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
> -			 unsigned int flags, struct page **pages, int *nr)
> +			 unsigned int flags, struct page **pages, int *nr,
> +			 struct vaddr_pin *vaddr_pin)
>  {
>  	struct dev_pagemap *pgmap = NULL;
>  	int nr_start = *nr, ret = 0;
> @@ -1894,7 +1895,8 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
>   * useful to have gup_huge_pmd even if we can't operate on ptes.
>   */
>  static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
> -			 unsigned int flags, struct page **pages, int *nr)
> +			 unsigned int flags, struct page **pages, int *nr,
> +			 struct vaddr_pin *vaddr_pin)
>  {
>  	return 0;
>  }
> @@ -1903,7 +1905,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
>  #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
>  static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr,
> -		unsigned int flags)
> +		unsigned int flags, struct vaddr_pin *vaddr_pin)
>  {
>  	int nr_start = *nr;
>  	struct dev_pagemap *pgmap = NULL;
> @@ -1938,13 +1940,14 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>  
>  static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr,
> -		unsigned int flags)
> +		unsigned int flags, struct vaddr_pin *vaddr_pin)
>  {
>  	unsigned long fault_pfn;
>  	int nr_start = *nr;
>  
>  	fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
> -	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr, flags))
> +	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr, flags,
> +			       vaddr_pin))
>  		return 0;
>  
>  	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
> @@ -1957,13 +1960,14 @@ static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  
>  static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr,
> -		unsigned int flags)
> +		unsigned int flags, struct vaddr_pin *vaddr_pin)
>  {
>  	unsigned long fault_pfn;
>  	int nr_start = *nr;
>  
>  	fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
> -	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr, flags))
> +	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr, flags,
> +			       vaddr_pin))
>  		return 0;
>  
>  	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
> @@ -1975,7 +1979,7 @@ static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
>  #else
>  static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr,
> -		unsigned int flags)
> +		unsigned int flags, struct vaddr_pin *vaddr_pin)
>  {
>  	BUILD_BUG();
>  	return 0;
> @@ -1983,7 +1987,7 @@ static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  
>  static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
>  		unsigned long end, struct page **pages, int *nr,
> -		unsigned int flags)
> +		unsigned int flags, struct vaddr_pin *vaddr_pin)
>  {
>  	BUILD_BUG();
>  	return 0;
> @@ -2075,7 +2079,8 @@ static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
>  #endif /* CONFIG_ARCH_HAS_HUGEPD */
>  
>  static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
> -		unsigned long end, unsigned int flags, struct page **pages, int *nr)
> +		unsigned long end, unsigned int flags, struct page **pages,
> +		int *nr, struct vaddr_pin *vaddr_pin)
>  {
>  	struct page *head, *page;
>  	int refs;
> @@ -2087,7 +2092,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  		if (unlikely(flags & FOLL_LONGTERM))
>  			return 0;
>  		return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr,
> -					     flags);
> +					     flags, vaddr_pin);
>  	}
>  
>  	refs = 0;
> @@ -2117,7 +2122,8 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
>  }
>  
>  static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
> -		unsigned long end, unsigned int flags, struct page **pages, int *nr)
> +		unsigned long end, unsigned int flags, struct page **pages, int *nr,
> +		struct vaddr_pin *vaddr_pin)
>  {
>  	struct page *head, *page;
>  	int refs;
> @@ -2129,7 +2135,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
>  		if (unlikely(flags & FOLL_LONGTERM))
>  			return 0;
>  		return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr,
> -					     flags);
> +					     flags, vaddr_pin);
>  	}
>  
>  	refs = 0;
> @@ -2196,7 +2202,8 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
>  }
>  
>  static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
> -		unsigned int flags, struct page **pages, int *nr)
> +		unsigned int flags, struct page **pages, int *nr,
> +		struct vaddr_pin *vaddr_pin)
>  {
>  	unsigned long next;
>  	pmd_t *pmdp;
> @@ -2220,7 +2227,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
>  				return 0;
>  
>  			if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
> -				pages, nr))
> +				pages, nr, vaddr_pin))
>  				return 0;
>  
>  		} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
> @@ -2231,7 +2238,8 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
>  			if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
>  					 PMD_SHIFT, next, flags, pages, nr))
>  				return 0;
> -		} else if (!gup_pte_range(pmd, addr, next, flags, pages, nr))
> +		} else if (!gup_pte_range(pmd, addr, next, flags, pages, nr,
> +					  vaddr_pin))
>  			return 0;
>  	} while (pmdp++, addr = next, addr != end);
>  
> @@ -2239,7 +2247,8 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
>  }
>  
>  static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
> -			 unsigned int flags, struct page **pages, int *nr)
> +			 unsigned int flags, struct page **pages, int *nr,
> +			 struct vaddr_pin *vaddr_pin)
>  {
>  	unsigned long next;
>  	pud_t *pudp;
> @@ -2253,13 +2262,14 @@ static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
>  			return 0;
>  		if (unlikely(pud_huge(pud))) {
>  			if (!gup_huge_pud(pud, pudp, addr, next, flags,
> -					  pages, nr))
> +					  pages, nr, vaddr_pin))
>  				return 0;
>  		} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
>  			if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
>  					 PUD_SHIFT, next, flags, pages, nr))
>  				return 0;
> -		} else if (!gup_pmd_range(pud, addr, next, flags, pages, nr))
> +		} else if (!gup_pmd_range(pud, addr, next, flags, pages, nr,
> +					  vaddr_pin))
>  			return 0;
>  	} while (pudp++, addr = next, addr != end);
>  
> @@ -2267,7 +2277,8 @@ static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
>  }
>  
>  static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
> -			 unsigned int flags, struct page **pages, int *nr)
> +			 unsigned int flags, struct page **pages, int *nr,
> +			 struct vaddr_pin *vaddr_pin)
>  {
>  	unsigned long next;
>  	p4d_t *p4dp;
> @@ -2284,7 +2295,8 @@ static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
>  			if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
>  					 P4D_SHIFT, next, flags, pages, nr))
>  				return 0;
> -		} else if (!gup_pud_range(p4d, addr, next, flags, pages, nr))
> +		} else if (!gup_pud_range(p4d, addr, next, flags, pages, nr,
> +					  vaddr_pin))
>  			return 0;
>  	} while (p4dp++, addr = next, addr != end);
>  
> @@ -2292,7 +2304,8 @@ static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
>  }
>  
>  static void gup_pgd_range(unsigned long addr, unsigned long end,
> -		unsigned int flags, struct page **pages, int *nr)
> +		unsigned int flags, struct page **pages, int *nr,
> +		struct vaddr_pin *vaddr_pin)
>  {
>  	unsigned long next;
>  	pgd_t *pgdp;
> @@ -2312,7 +2325,8 @@ static void gup_pgd_range(unsigned long addr, unsigned long end,
>  			if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
>  					 PGDIR_SHIFT, next, flags, pages, nr))
>  				return;
> -		} else if (!gup_p4d_range(pgd, addr, next, flags, pages, nr))
> +		} else if (!gup_p4d_range(pgd, addr, next, flags, pages, nr,
> +					  vaddr_pin))
>  			return;
>  	} while (pgdp++, addr = next, addr != end);
>  }
> @@ -2374,7 +2388,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
>  	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
>  	    gup_fast_permitted(start, end)) {
>  		local_irq_save(flags);
> -		gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr);
> +		gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr,
> +			      NULL);
>  		local_irq_restore(flags);
>  	}
>  
> @@ -2445,7 +2460,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
>  	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
>  	    gup_fast_permitted(start, end)) {
>  		local_irq_disable();
> -		gup_pgd_range(addr, end, gup_flags, pages, &nr);
> +		gup_pgd_range(addr, end, gup_flags, pages, &nr, NULL);
>  		local_irq_enable();
>  		ret = nr;
>  	}
> 

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