[PATCH 76/94] mm/khugepaged: Use maple tree iterators instead of vma

[Hillf Danton]

On Wed, 28 Apr 2021 15:36:24  Liam R. Howlett wrote:
> ---
>  mm/khugepaged.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)

Good work. And a nit below.
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 33cf91529f0b..4983a25c5a90 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2063,6 +2063,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned =
> int pages,
>  	struct mm_struct *mm;
>  	struct vm_area_struct *vma;
>  	int progress = 0;
> +	MA_STATE(mas, NULL, 0, 0);
> 
>  	VM_BUG_ON(!pages);
>  	lockdep_assert_held(&khugepaged_mm_lock);
> @@ -2079,18 +2080,22 @@ static unsigned int khugepaged_scan_mm_slot(unsigne=
> d int pages,
>  	khugepaged_collapse_pte_mapped_thps(mm_slot);
> 
>  	mm = mm_slot->mm;
> +	mas.tree = &mm->mm_mt;
>  	/*
>  	 * Don't wait for semaphore (to avoid long wait times).  Just move to
>  	 * the next mm on the list.
>  	 */
>  	vma = NULL;
> +	mas_set(&mas, khugepaged_scan.address);
>  	if (unlikely(!mmap_read_trylock(mm)))
>  		goto breakouterloop_mmap_lock;
> +
> +	rcu_read_lock();
>  	if (likely(!khugepaged_test_exit(mm)))
> -		vma = find_vma(mm, khugepaged_scan.address);
> +		vma = mas_find(&mas, ULONG_MAX);
> 
>  	progress++;
> -	for (; vma; vma = vma->vm_next) {
> +	mas_for_each(&mas, vma, ULONG_MAX) {
>  		unsigned long hstart, hend;
> 
>  		cond_resched();

Given the added rcu_read_lock(), take another look at this scheduling
entry?

> @@ -2129,6 +2134,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned =
> int pages,
>  				pgoff_t pgoff = linear_page_index(vma,
>  						khugepaged_scan.address);
> 
> +				rcu_read_unlock();
>  				mmap_read_unlock(mm);
>  				ret = 1;
>  				khugepaged_scan_file(mm, file, pgoff, hpage);
> @@ -2149,6 +2155,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned =
> int pages,
>  		}
>  	}
>  breakouterloop:
> +	rcu_read_unlock();
>  	mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */
>  breakouterloop_mmap_lock:
> 
> --
> 2.30.2