The quilt patch titled
Subject: mm: rmap: move the cache flushing to the correct place for hugetlb PMD sharing
has been removed from the -mm tree. Its filename was
mm-rmap-move-the-cache-flushing-to-the-correct-place-for-hugetlb-pmd-sharing.patch
This patch was dropped because it was merged into mm-stable
------------------------------------------------------
From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Subject: mm: rmap: move the cache flushing to the correct place for hugetlb PMD sharing
The cache level flush will always be first when changing an existing
virtualâ??>physical mapping to a new value, since this allows us to
properly handle systems whose caches are strict and require a
virtualâ??>physical translation to exist for a virtual address. So we
should move the cache flushing before huge_pmd_unshare().
As Muchun pointed out[1], now the architectures whose supporting hugetlb
PMD sharing have no cache flush issues in practice. But I think we should
still follow the cache/TLB flushing rules when changing a valid virtual
address mapping in case of potential issues in future.
[1] https://lore.kernel.org/all/YmT%2F%2FhuUbFX+KHcy@xxxxxxxxxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/4f7ae6dfdc838ab71e1655188b657c032ff1f28f.1651056365.git.baolin.wang@xxxxxxxxxxxxxxxxx
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mina Almasry <almasrymina@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/rmap.c | 40 ++++++++++++++++++++++------------------
1 file changed, 22 insertions(+), 18 deletions(-)
--- a/mm/rmap.c~mm-rmap-move-the-cache-flushing-to-the-correct-place-for-hugetlb-pmd-sharing
+++ a/mm/rmap.c
@@ -1532,15 +1532,16 @@ static bool try_to_unmap_one(struct foli
* do this outside rmap routines.
*/
VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+ /*
+ * huge_pmd_unshare may unmap an entire PMD page.
+ * There is no way of knowing exactly which PMDs may
+ * be cached for this mm, so we must flush them all.
+ * start/end were already adjusted above to cover this
+ * range.
+ */
+ flush_cache_range(vma, range.start, range.end);
+
if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
- /*
- * huge_pmd_unshare unmapped an entire PMD
- * page. There is no way of knowing exactly
- * which PMDs may be cached for this mm, so
- * we must flush them all. start/end were
- * already adjusted above to cover this range.
- */
- flush_cache_range(vma, range.start, range.end);
flush_tlb_range(vma, range.start, range.end);
mmu_notifier_invalidate_range(mm, range.start,
range.end);
@@ -1557,13 +1558,14 @@ static bool try_to_unmap_one(struct foli
page_vma_mapped_walk_done(&pvmw);
break;
}
+ } else {
+ flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
}
/*
* Nuke the page table entry. When having to clear
* PageAnonExclusive(), we always have to flush.
*/
- flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
if (should_defer_flush(mm, flags) && !anon_exclusive) {
/*
* We clear the PTE but do not flush so potentially
@@ -1884,15 +1886,16 @@ static bool try_to_migrate_one(struct fo
* do this outside rmap routines.
*/
VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+ /*
+ * huge_pmd_unshare may unmap an entire PMD page.
+ * There is no way of knowing exactly which PMDs may
+ * be cached for this mm, so we must flush them all.
+ * start/end were already adjusted above to cover this
+ * range.
+ */
+ flush_cache_range(vma, range.start, range.end);
+
if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
- /*
- * huge_pmd_unshare unmapped an entire PMD
- * page. There is no way of knowing exactly
- * which PMDs may be cached for this mm, so
- * we must flush them all. start/end were
- * already adjusted above to cover this range.
- */
- flush_cache_range(vma, range.start, range.end);
flush_tlb_range(vma, range.start, range.end);
mmu_notifier_invalidate_range(mm, range.start,
range.end);
@@ -1909,10 +1912,11 @@ static bool try_to_migrate_one(struct fo
page_vma_mapped_walk_done(&pvmw);
break;
}
+ } else {
+ flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
}
/* Nuke the page table entry. */
- flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
pteval = ptep_clear_flush(vma, address, pvmw.pte);
/* Set the dirty flag on the folio now the pte is gone. */
_
Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are
