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Date: Sat, 31 May 2008 13:21:13 +0100
From: Mel Gorman <mel@....ul.ie>
To: Andy Whitcroft <apw@...dowen.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, agl@...ibm.com, wli@...omorphy.com,
kenchen@...gle.com, dwg@....ibm.com, andi@...stfloor.org,
dean@...tic.org, abh@...y.com
Subject: Re: [PATCH 1/2] huge page private reservation review cleanups
On (30/05/08 17:58), Andy Whitcroft didst pronounce:
>
> Create some new accessors for vma private data to cut down on and contain
> the casts. Encapsulates the huge and small page offset calculations. Also
> adds a couple of VM_BUG_ONs for consistency.
>
Things are a bit more readable with the helpers for sure. Thanks for catching
the missing VM_BUG_ONs as well.
> Signed-off-by: Andy Whitcroft <apw@...dowen.org>
Acked-by: Mel Gorman <mel@....ul.ie>
> ---
> mm/hugetlb.c | 56 +++++++++++++++++++++++++++++++++++++++++++-------------
> 1 files changed, 43 insertions(+), 13 deletions(-)
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 729a830..7a5ac81 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -40,6 +40,26 @@ static int hugetlb_next_nid;
> */
> static DEFINE_SPINLOCK(hugetlb_lock);
>
> +/*
> + * Convert the address within this vma to the page offset within
> + * the mapping, in base page units.
> + */
> +pgoff_t vma_page_offset(struct vm_area_struct *vma, unsigned long address)
> +{
> + return ((address - vma->vm_start) >> PAGE_SHIFT) +
> + (vma->vm_pgoff >> PAGE_SHIFT);
> +}
> +
> +/*
> + * Convert the address within this vma to the page offset within
> + * the mapping, in pagecache page units; huge pages here.
> + */
> +pgoff_t vma_pagecache_offset(struct vm_area_struct *vma, unsigned long address)
> +{
> + return ((address - vma->vm_start) >> HPAGE_SHIFT) +
> + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
> +}
> +
> #define HPAGE_RESV_OWNER (1UL << (BITS_PER_LONG - 1))
> #define HPAGE_RESV_UNMAPPED (1UL << (BITS_PER_LONG - 2))
> #define HPAGE_RESV_MASK (HPAGE_RESV_OWNER | HPAGE_RESV_UNMAPPED)
> @@ -53,36 +73,48 @@ static DEFINE_SPINLOCK(hugetlb_lock);
> * to reset the VMA at fork() time as it is not in use yet and there is no
> * chance of the global counters getting corrupted as a result of the values.
> */
> +static unsigned long get_vma_private_data(struct vm_area_struct *vma)
> +{
> + return (unsigned long)vma->vm_private_data;
> +}
> +
> +static void set_vma_private_data(struct vm_area_struct *vma,
> + unsigned long value)
> +{
> + vma->vm_private_data = (void *)value;
> +}
> +
> static unsigned long vma_resv_huge_pages(struct vm_area_struct *vma)
> {
> VM_BUG_ON(!is_vm_hugetlb_page(vma));
> if (!(vma->vm_flags & VM_SHARED))
> - return (unsigned long)vma->vm_private_data & ~HPAGE_RESV_MASK;
> + return get_vma_private_data(vma) & ~HPAGE_RESV_MASK;
> return 0;
> }
>
> static void set_vma_resv_huge_pages(struct vm_area_struct *vma,
> unsigned long reserve)
> {
> - unsigned long flags;
> VM_BUG_ON(!is_vm_hugetlb_page(vma));
> VM_BUG_ON(vma->vm_flags & VM_SHARED);
>
> - flags = (unsigned long)vma->vm_private_data & HPAGE_RESV_MASK;
> - vma->vm_private_data = (void *)(reserve | flags);
> + set_vma_private_data(vma,
> + (get_vma_private_data(vma) & HPAGE_RESV_MASK) | reserve);
> }
>
> static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
> {
> - unsigned long reserveflags = (unsigned long)vma->vm_private_data;
> VM_BUG_ON(!is_vm_hugetlb_page(vma));
> - vma->vm_private_data = (void *)(reserveflags | flags);
> + VM_BUG_ON(vma->vm_flags & VM_SHARED);
> +
> + set_vma_private_data(vma, get_vma_private_data(vma) | flags);
> }
>
> static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
> {
> VM_BUG_ON(!is_vm_hugetlb_page(vma));
> - return ((unsigned long)vma->vm_private_data & flag) != 0;
> +
> + return (get_vma_private_data(vma) & flag) != 0;
> }
>
> /* Decrement the reserved pages in the hugepage pool by one */
> @@ -1150,11 +1182,10 @@ static struct page *hugetlbfs_pagecache_page(struct vm_area_struct *vma,
> unsigned long address)
> {
> struct address_space *mapping;
> - unsigned long idx;
> + pgoff_t idx;
>
> mapping = vma->vm_file->f_mapping;
> - idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
> - + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
> + idx = vma_pagecache_offset(vma, address);
>
> return find_lock_page(mapping, idx);
> }
> @@ -1163,7 +1194,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
> unsigned long address, pte_t *ptep, int write_access)
> {
> int ret = VM_FAULT_SIGBUS;
> - unsigned long idx;
> + pgoff_t idx;
> unsigned long size;
> struct page *page;
> struct address_space *mapping;
> @@ -1182,8 +1213,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
> }
>
> mapping = vma->vm_file->f_mapping;
> - idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
> - + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
> + idx = vma_pagecache_offset(vma, address);
>
> /*
> * Use page lock to guard against racing truncation
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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