[PATCH v1 06/16] mm/oom_kill: factor out zapping of VMA into zap_vma_for_reaping()

David Hildenbrand (Arm)
2026-02-27T20:10:52Z

Let's factor it out so we can turn unmap_page_range() into a static
function instead, and so oom reaping has a clean interface to call.

Note that hugetlb is not supported, because it would require a bunch of
hugetlb-specific further actions (see zap_page_range_single_batched()).

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
mm/internal.h | 5 +----
mm/memory.c | 36 ++++++++++++++++++++++++++++++++----
mm/oom_kill.c | 15 +--------------
3 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 39ab37bb0e1d..df9190f7db0e 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -536,13 +536,10 @@ static inline void sync_with_folio_pmd_zap(struct mm_struct *mm, pmd_t *pmdp)
}

struct zap_details;
-void unmap_page_range(struct mmu_gather *tlb,
- struct vm_area_struct *vma,
- unsigned long addr, unsigned long end,
- struct zap_details *details);
void zap_page_range_single_batched(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long addr,
unsigned long size, struct zap_details *details);
+int zap_vma_for_reaping(struct vm_area_struct *vma);
int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
gfp_t gfp);

diff --git a/mm/memory.c b/mm/memory.c
index e4154f03feac..621f38ae1425 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2054,10 +2054,9 @@ static inline unsigned long zap_p4d_range(struct mmu_gather *tlb,
return addr;
}

-void unmap_page_range(struct mmu_gather *tlb,
- struct vm_area_struct *vma,
- unsigned long addr, unsigned long end,
- struct zap_details *details)
+static void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ unsigned long addr, unsigned long end,
+ struct zap_details *details)
{
pgd_t *pgd;
unsigned long next;
@@ -2115,6 +2114,35 @@ static void unmap_single_vma(struct mmu_gather *tlb,
}
}

+/**
+ * zap_vma_for_reaping - zap all page table entries in the vma without blocking
+ * @vma: The vma to zap.
+ *
+ * Zap all page table entries in the vma without blocking for use by the oom
+ * killer. Hugetlb vmas are not supported.
+ *
+ * Returns: 0 on success, -EBUSY if we would have to block.
+ */
+int zap_vma_for_reaping(struct vm_area_struct *vma)
+{
+ struct mmu_notifier_range range;
+ struct mmu_gather tlb;
+
+ VM_WARN_ON_ONCE(is_vm_hugetlb_page(vma));
+
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
+ vma->vm_start, vma->vm_end);
+ tlb_gather_mmu(&tlb, vma->vm_mm);
+ if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
+ tlb_finish_mmu(&tlb);
+ return -EBUSY;
+ }
+ unmap_page_range(&tlb, vma, range.start, range.end, NULL);
+ mmu_notifier_invalidate_range_end(&range);
+ tlb_finish_mmu(&tlb);
+ return 0;
+}
+
/**
* unmap_vmas - unmap a range of memory covered by a list of vma's
* @tlb: address of the caller's struct mmu_gather
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 0ba56fcd10d5..54b7a8fe5136 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -548,21 +548,8 @@ static bool __oom_reap_task_mm(struct mm_struct *mm)
* count elevated without a good reason.
*/
if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
- struct mmu_notifier_range range;
- struct mmu_gather tlb;
-
- mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0,
- mm, vma->vm_start,
- vma->vm_end);
- tlb_gather_mmu(&tlb, mm);
- if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
- tlb_finish_mmu(&tlb);
+ if (zap_vma_for_reaping(vma))
ret = false;
- continue;
- }
- unmap_page_range(&tlb, vma, range.start, range.end, NULL);
- mmu_notifier_invalidate_range_end(&range);
- tlb_finish_mmu(&tlb);
}
}

--
2.43.0