lkml.org 
[lkml]   [2008]   [May]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/2] huge page private reservation review cleanups
On Fri, 30 May 2008 17:58:24 +0100
Andy Whitcroft <apw@shadowen.org> wrote:

>
> 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.
>

I'll stage this after Mel's
hugetlb-guarantee-that-cow-faults-for-a-process-that-called-mmapmap_private-on-hugetlbfs-will-succeed.patch

> ---
> 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));
> +}

I'll make these static.

> #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;
> +}

Better.

> 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;
> }

But I wonder if helpers which manipulate a vma's HPAGE_RESV_MASK
flag(s) rather than the whole vm_provate_data would have been better.

> 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;
> }

Oh. We already kinda have it. Perhaps vma_resv_huge_pages() should
have called set_vma_resv_flags(). I guess the assertions would have
busted that.

Oh well, whatever.



\
 
 \ /
  Last update: 2008-05-30 22:33    [W:0.048 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site