On 17/12/24 10:52 pm, Ryan Roberts wrote:
On 16/12/2024 16:50, Dev Jain wrote:
Upon failure, we repopulate the PMD in case of PMD-THP collapse. Hence, make
this logic specific for PMD case.
Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
---
mm/khugepaged.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index de044b1f83d4..886c76816963 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -766,7 +766,7 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
pmd_t *pmd,
pmd_t orig_pmd,
struct vm_area_struct *vma,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist, int order)
nit: suggest putting order on its own line.
{
spinlock_t *pmd_ptl;
@@ -776,14 +776,16 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
* pages. Since pages are still isolated and locked here,
* acquiring anon_vma_lock_write is unnecessary.
*/
- pmd_ptl = pmd_lock(vma->vm_mm, pmd);
- pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
- spin_unlock(pmd_ptl);
+ if (order == HPAGE_PMD_ORDER) {
+ pmd_ptl = pmd_lock(vma->vm_mm, pmd);
+ pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
+ spin_unlock(pmd_ptl);
+ }
/*
* Release both raw and compound pages isolated
* in __collapse_huge_page_isolate.
*/
- release_pte_pages(pte, pte + HPAGE_PMD_NR, compound_pagelist);
+ release_pte_pages(pte, pte + (1UL << order), compound_pagelist);
}
Given this function is clearly so geared towards re-establishing the pmd, given
that it takes the *pmd and orig_pmd as params, and given that in the
non-pmd-order case, we only call through to release_pte_pages(), I wonder if
it's better to make the decision at a higher level and either call this function
or release_pte_pages() directly? No strong opinion, just looks a bit weird at
the moment.
Makes sense, we can probably get rid of this function and let the caller call
reestablish_pmd() or something for the PMD case.
/*
@@ -834,7 +836,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
compound_pagelist);
else
__collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
- compound_pagelist);
+ compound_pagelist, order);
return result;
}
