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Date: Mon, 20 Jun 2022 19:47:15 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org
Cc: mike.kravetz@...cle.com, songmuchun@...edance.com,
baolin.wang@...ux.alibaba.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH] mm: rmap: Simplify the hugetlb handling when unmapping or migration
According to previous discussion [1], there are so many levels of indenting
to handle the hugetlb case when unmapping or migration. We can combine
folio_test_anon() and huge_pmd_unshare() to save one level of indenting,
by adding a local variable and moving the VM_BUG_ON() a little forward.
No intended functional changes in this patch.
[1] https://lore.kernel.org/all/0b986dc4-5843-3e2d-c2df-5a2e9f13e6ab@oracle.com/
Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
mm/rmap.c | 90 +++++++++++++++++++++++++++++++--------------------------------
1 file changed, 44 insertions(+), 46 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 04fac1a..2f48a54 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1537,6 +1537,8 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
PageAnonExclusive(subpage);
if (folio_test_hugetlb(folio)) {
+ bool anon = folio_test_anon(folio);
+
/*
* The try_to_unmap() is only passed a hugetlb page
* in the case where the hugetlb page is poisoned.
@@ -1551,31 +1553,28 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
*/
flush_cache_range(vma, range.start, range.end);
- if (!folio_test_anon(folio)) {
+ /*
+ * To call huge_pmd_unshare, i_mmap_rwsem must be
+ * held in write mode. Caller needs to explicitly
+ * do this outside rmap routines.
+ */
+ VM_BUG_ON(!anon && !(flags & TTU_RMAP_LOCKED));
+ if (!anon && huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
+ flush_tlb_range(vma, range.start, range.end);
+ mmu_notifier_invalidate_range(mm, range.start,
+ range.end);
+
/*
- * To call huge_pmd_unshare, i_mmap_rwsem must be
- * held in write mode. Caller needs to explicitly
- * do this outside rmap routines.
+ * The ref count of the PMD page was dropped
+ * which is part of the way map counting
+ * is done for shared PMDs. Return 'true'
+ * here. When there is no other sharing,
+ * huge_pmd_unshare returns false and we will
+ * unmap the actual page and drop map count
+ * to zero.
*/
- VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
-
- if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
- flush_tlb_range(vma, range.start, range.end);
- mmu_notifier_invalidate_range(mm, range.start,
- range.end);
-
- /*
- * The ref count of the PMD page was dropped
- * which is part of the way map counting
- * is done for shared PMDs. Return 'true'
- * here. When there is no other sharing,
- * huge_pmd_unshare returns false and we will
- * unmap the actual page and drop map count
- * to zero.
- */
- page_vma_mapped_walk_done(&pvmw);
- break;
- }
+ page_vma_mapped_walk_done(&pvmw);
+ break;
}
pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
} else {
@@ -1906,6 +1905,8 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
PageAnonExclusive(subpage);
if (folio_test_hugetlb(folio)) {
+ bool anon = folio_test_anon(folio);
+
/*
* huge_pmd_unshare may unmap an entire PMD page.
* There is no way of knowing exactly which PMDs may
@@ -1915,31 +1916,28 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
*/
flush_cache_range(vma, range.start, range.end);
- if (!folio_test_anon(folio)) {
+ /*
+ * To call huge_pmd_unshare, i_mmap_rwsem must be
+ * held in write mode. Caller needs to explicitly
+ * do this outside rmap routines.
+ */
+ VM_BUG_ON(!anon && !(flags & TTU_RMAP_LOCKED));
+ if (!anon && huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
+ flush_tlb_range(vma, range.start, range.end);
+ mmu_notifier_invalidate_range(mm, range.start,
+ range.end);
+
/*
- * To call huge_pmd_unshare, i_mmap_rwsem must be
- * held in write mode. Caller needs to explicitly
- * do this outside rmap routines.
+ * The ref count of the PMD page was dropped
+ * which is part of the way map counting
+ * is done for shared PMDs. Return 'true'
+ * here. When there is no other sharing,
+ * huge_pmd_unshare returns false and we will
+ * unmap the actual page and drop map count
+ * to zero.
*/
- VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
-
- if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
- flush_tlb_range(vma, range.start, range.end);
- mmu_notifier_invalidate_range(mm, range.start,
- range.end);
-
- /*
- * The ref count of the PMD page was dropped
- * which is part of the way map counting
- * is done for shared PMDs. Return 'true'
- * here. When there is no other sharing,
- * huge_pmd_unshare returns false and we will
- * unmap the actual page and drop map count
- * to zero.
- */
- page_vma_mapped_walk_done(&pvmw);
- break;
- }
+ page_vma_mapped_walk_done(&pvmw);
+ break;
}
/* Nuke the hugetlb page table entry */
--
1.8.3.1
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