Hi, Nico
Some nit below.
On Tue, Aug 19, 2025 at 07:41:55AM -0600, Nico Pache wrote:
>For khugepaged to support different mTHP orders, we must generalize this
>to check if the PMD is not shared by another VMA and the order is enabled.
>
>To ensure madvise_collapse can support working on mTHP orders without the
>PMD order enabled, we need to convert hugepage_vma_revalidate to take a
>bitmap of orders.
>
>No functional change in this patch.
>
>Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
>Acked-by: David Hildenbrand <david@xxxxxxxxxx>
>Co-developed-by: Dev Jain <dev.jain@xxxxxxx>
>Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
>Signed-off-by: Nico Pache <npache@xxxxxxxxxx>
>---
> mm/khugepaged.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
>diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>index b7b98aebb670..2d192ec961d2 100644
>--- a/mm/khugepaged.c
>+++ b/mm/khugepaged.c
There is a comment above this function, which says "revalidate vma before
taking mmap_lock".
I am afraid it is "after taking mmap_lock"? or "after taking mmap_lock again"?
>@@ -917,7 +917,7 @@ static int collapse_find_target_node(struct collapse_control *cc)
> static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> bool expect_anon,
> struct vm_area_struct **vmap,
>- struct collapse_control *cc)
>+ struct collapse_control *cc, unsigned long orders)
> {
> struct vm_area_struct *vma;
> enum tva_type type = cc->is_khugepaged ? TVA_KHUGEPAGED :
>@@ -930,9 +930,10 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> if (!vma)
> return SCAN_VMA_NULL;
>
>+ /* Always check the PMD order to insure its not shared by another VMA */
> if (!thp_vma_suitable_order(vma, address, PMD_ORDER))
> return SCAN_ADDRESS_RANGE;
>- if (!thp_vma_allowable_order(vma, vma->vm_flags, type, PMD_ORDER))
>+ if (!thp_vma_allowable_orders(vma, vma->vm_flags, type, orders))
> return SCAN_VMA_CHECK;
> /*
> * Anon VMA expected, the address may be unmapped then
Below is a comment, "thp_vma_allowable_order may return".
Since you use thp_vma_allowable_orders, maybe we need to change the comment
too.
>@@ -1134,7 +1135,8 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> goto out_nolock;
>
> mmap_read_lock(mm);
>- result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
>+ result = hugepage_vma_revalidate(mm, address, true, &vma, cc,
>+ BIT(HPAGE_PMD_ORDER));
> if (result != SCAN_SUCCEED) {
> mmap_read_unlock(mm);
> goto out_nolock;
>@@ -1168,7 +1170,8 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> * mmap_lock.
> */
> mmap_write_lock(mm);
>- result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
>+ result = hugepage_vma_revalidate(mm, address, true, &vma, cc,
>+ BIT(HPAGE_PMD_ORDER));
> if (result != SCAN_SUCCEED)
> goto out_up_write;
> /* check if the pmd is still valid */
>@@ -2807,7 +2810,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
> mmap_read_lock(mm);
> mmap_locked = true;
> result = hugepage_vma_revalidate(mm, addr, false, &vma,
>- cc);
>+ cc, BIT(HPAGE_PMD_ORDER));
> if (result != SCAN_SUCCEED) {
> last_fail = result;
> goto out_nolock;
>--
>2.50.1
>
--
Wei Yang
Help you, Help me
