在 2023/3/6 下午5:22, Yin Fengwei 写道:
If unmap one page fails, or the vma walk will skip next pte,
or the vma walk will end on next pte, batched remove map,
update folio refcount.
Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
---
include/linux/rmap.h | 1 +
mm/page_vma_mapped.c | 30 +++++++++++++++++++++++++++
mm/rmap.c | 48 ++++++++++++++++++++++++++++++++++----------
3 files changed, 68 insertions(+), 11 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index d2569b42e21a..18193d1d5a8e 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -424,6 +424,7 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
}
bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
+bool pvmw_walk_skip_or_end_on_next(struct page_vma_mapped_walk *pvmw);
/*
* Used by swapoff to help locate where page is expected in vma.
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 4e448cfbc6ef..19e997dfb5c6 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -291,6 +291,36 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
return false;
}
+/**
+ * pvmw_walk_skip_or_end_on_next - check if next pte will be skipped or
+ * end the walk
+ * @pvmw: pointer to struct page_vma_mapped_walk.
+ *
+ * This function can only be called with correct pte lock hold
+ */
+bool pvmw_walk_skip_or_end_on_next(struct page_vma_mapped_walk *pvmw)
+{
+ unsigned long address = pvmw->address + PAGE_SIZE;
+
+ if (address >= vma_address_end(pvmw))
+ return true;
If vma_address_end is exactly equal to next address(pvmw->address +
PAGE_SIZE) , does this mean that we are ignored to unmap the last page
here ? so
there can just use ' > ' ' if (address > vma_address_end(pvmw))' .
I may have misunderstood, please correct me.
+
+ if ((address & (PMD_SIZE - PAGE_SIZE)) == 0)
+ return true;
+
+ if (pte_none(*pvmw->pte))
+ return true;
+
+ pvmw->pte++;
+ if (!check_pte(pvmw)) {
+ pvmw->pte--;
+ return true;
+ }
+ pvmw->pte--;
+
+ return false;
+}
+
/**
* page_mapped_in_vma - check whether a page is really mapped in a VMA
* @page: the page to test
diff --git a/mm/rmap.c b/mm/rmap.c
index bb3fcb8df579..a64e9cbb52dd 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1741,6 +1741,26 @@ static bool try_to_unmap_one_page(struct folio *folio,
return false;
}
+static void folio_remove_rmap_and_update_count(struct folio *folio,
+ struct page *start, struct vm_area_struct *vma, int count)
+{
+ if (count == 0)
+ return;
+
+ /*
+ * No need to call mmu_notifier_invalidate_range() it has be
+ * done above for all cases requiring it to happen under page
+ * table lock before mmu_notifier_invalidate_range_end()
+ *
+ * See Documentation/mm/mmu_notifier.rst
+ */
+ folio_remove_rmap_range(folio, start, count, vma,
+ folio_test_hugetlb(folio));
+ if (vma->vm_flags & VM_LOCKED)
+ mlock_drain_local();
+ folio_ref_sub(folio, count);
+}
+
/*
* @arg: enum ttu_flags will be passed to this argument
*/
@@ -1748,10 +1768,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
unsigned long address, void *arg)
{
DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
- struct page *subpage;
+ struct page *start = NULL;
bool ret = true;
struct mmu_notifier_range range;
enum ttu_flags flags = (enum ttu_flags)(long)arg;
+ int count = 0;
/*
* When racing against e.g. zap_pte_range() on another cpu,
@@ -1812,26 +1833,31 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
break;
}
- subpage = folio_page(folio,
+ if (!start)
+ start = folio_page(folio,
pte_pfn(*pvmw.pte) - folio_pfn(folio));
ret = try_to_unmap_one_page(folio, vma,
range, pvmw, address, flags);
if (!ret) {
+ folio_remove_rmap_and_update_count(folio,
+ start, vma, count);
page_vma_mapped_walk_done(&pvmw);
break;
}
+ count++;
/*
- * No need to call mmu_notifier_invalidate_range() it has be
- * done above for all cases requiring it to happen under page
- * table lock before mmu_notifier_invalidate_range_end()
- *
- * See Documentation/mm/mmu_notifier.rst
+ * If next pte will be skipped in page_vma_mapped_walk() or
+ * the walk will end at it, batched remove rmap and update
+ * page refcount. We can't do it after page_vma_mapped_walk()
+ * return false because the pte lock will not be hold.
*/
- page_remove_rmap(subpage, vma, false);
- if (vma->vm_flags & VM_LOCKED)
- mlock_drain_local();
- folio_put(folio);
+ if (pvmw_walk_skip_or_end_on_next(&pvmw)) {
+ folio_remove_rmap_and_update_count(folio,
+ start, vma, count);
+ count = 0;
+ start = NULL;
+ }
}
mmu_notifier_invalidate_range_end(&range);
