linux-kernel - Re: [PATCH v13 52/70] mm/khugepaged: stop using vma linked list

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Date:   Tue, 6 Sep 2022 09:51:32 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Liam Howlett <liam.howlett@...cle.com>
Cc:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>
Subject: Re: [PATCH v13 52/70] mm/khugepaged: stop using vma linked list

On Mon, 22 Aug 2022, Liam Howlett wrote:

>From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
>
>Use vma iterator & find_vma() instead of vma linked list.
>
>Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
>Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>

Reviewed-by: Davidlohr Bueso <dave@...olabs.net>

>---
> mm/huge_memory.c |  4 ++--
> mm/khugepaged.c  | 11 ++++++++---
> 2 files changed, 10 insertions(+), 5 deletions(-)
>
>diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>index 83c47a989260..6c5c23ef658a 100644
>--- a/mm/huge_memory.c
>+++ b/mm/huge_memory.c
>@@ -2339,11 +2339,11 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma,
>	split_huge_pmd_if_needed(vma, end);
>
>	/*
>-	 * If we're also updating the vma->vm_next->vm_start,
>+	 * If we're also updating the next vma vm_start,
>	 * check if we need to split it.
>	 */
>	if (adjust_next > 0) {
>-		struct vm_area_struct *next = vma->vm_next;
>+		struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end);
>		unsigned long nstart = next->vm_start;
>		nstart += adjust_next;
>		split_huge_pmd_if_needed(next, nstart);
>diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>index d3313b7a8fe5..d8e388106322 100644
>--- a/mm/khugepaged.c
>+++ b/mm/khugepaged.c
>@@ -2053,10 +2053,12 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
>	__releases(&khugepaged_mm_lock)
>	__acquires(&khugepaged_mm_lock)
> {
>+	struct vma_iterator vmi;
>	struct mm_slot *mm_slot;
>	struct mm_struct *mm;
>	struct vm_area_struct *vma;
>	int progress = 0;
>+	unsigned long address;

Nit: just use khugepaged_scan.address.

>
>	VM_BUG_ON(!pages);
>	lockdep_assert_held(&khugepaged_mm_lock);
>@@ -2081,11 +2083,14 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
>	vma = NULL;
>	if (unlikely(!mmap_read_trylock(mm)))
>		goto breakouterloop_mmap_lock;
>-	if (likely(!hpage_collapse_test_exit(mm)))
>-		vma = find_vma(mm, khugepaged_scan.address);
>
>	progress++;
>-	for (; vma; vma = vma->vm_next) {
>+	if (unlikely(hpage_collapse_test_exit(mm)))
>+		goto breakouterloop;
>+
>+	address = khugepaged_scan.address;
>+	vma_iter_init(&vmi, mm, address);
>+	for_each_vma(vmi, vma) {
>		unsigned long hstart, hend;
>
>		cond_resched();
>
>--
>2.35.1
>