On Fri, 13 Jan 2012 19:44:53 +0800
Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> wrote:
> Afte call find_vma_prev(mm, addr, &prev_vma), following condition is always
> true:
> !prev_vma || (addr >= prev_vma->vm_end)
> it can be happily drop prev_vma and use find_vma instead of find_vma_prev
I had to rework this patch due to 097d59106a8e4b ("vm: avoid using
find_vma_prev() unnecessarily") in mainline. Can you please check my
handiwork?
From: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
Subject: hugetlb: drop prev_vma in hugetlb_get_unmapped_area_topdown()
After the call find_vma_prev(mm, addr, &prev_vma), the following condition
is always true:
!prev_vma || (addr >= prev_vma->vm_end)
it can happily drop prev_vma and use find_vma() instead of find_vma_prev().
Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Hillf Danton <dhillf@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/hugetlbpage.c | 23 +++++++----------------
1 file changed, 7 insertions(+), 16 deletions(-)
diff -puN arch/x86/mm/hugetlbpage.c~hugetlb-drop-prev_vma-in-hugetlb_get_unmapped_area_topdown arch/x86/mm/hugetlbpage.c
--- a/arch/x86/mm/hugetlbpage.c~hugetlb-drop-prev_vma-in-hugetlb_get_unmapped_area_topdown
+++ a/arch/x86/mm/hugetlbpage.c
@@ -308,7 +308,7 @@ static unsigned long hugetlb_get_unmappe
{
struct hstate *h = hstate_file(file);
struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma, *prev_vma;
+ struct vm_area_struct *vma;
unsigned long base = mm->mmap_base, addr = addr0;
unsigned long largest_hole = mm->cached_hole_size;
int first_time = 1;
@@ -334,25 +334,16 @@ try_again:
* i.e. return with success:
*/
vma = find_vma(mm, addr);
- if (!vma)
- return addr;
-
- /*
- * new region fits between prev_vma->vm_end and
- * vma->vm_start, use it:
- */
- prev_vma = vma->vm_prev;
- if (addr + len <= vma->vm_start &&
- (!prev_vma || (addr >= prev_vma->vm_end))) {
+ if (vma)
+ prev_vma = vma->vm_prev;
+ if (!vma || addr + len <= vma->vm_start) {
/* remember the address as a hint for next time */
mm->cached_hole_size = largest_hole;
return (mm->free_area_cache = addr);
- } else {
+ } else if (mm->free_area_cache == vma->vm_end) {
/* pull free_area_cache down to the first hole */
- if (mm->free_area_cache == vma->vm_end) {
- mm->free_area_cache = vma->vm_start;
- mm->cached_hole_size = largest_hole;
- }
+ mm->free_area_cache = vma->vm_start;
+ mm->cached_hole_size = largest_hole;
}
/* remember the largest hole we saw so far */
_
--
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