Re: linux-next: manual merge of the akpm tree with Linus' tree

Andrew Morton
2012-03-08T07:30:19Z

On Thu, 8 Mar 2012 17:53:07 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:

> Hi Andrew,
>
> Today's linux-next merge of the akpm tree got a conflict in
> arch/x86/mm/hugetlbpage.c between commit 097d59106a8e ("vm: avoid using
> find_vma_prev() unnecessarily") from Linus' tree and commit "hugetlb:
> drop prev_vma in hugetlb_get_unmapped_area_topdown()" from the akpm tree.
>
> I think the latter is a superset of the former, so I just dropped the
> changes from the former.

Actually they're different. I reworked the earlier patch as below.

From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
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@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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 */
_