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authorBaolin Wang <baolin.wang@linux.alibaba.com>2022-05-10 04:20:53 +0300
committerAndrew Morton <akpm@linux-foundation.org>2022-05-13 17:20:07 +0300
commit54205e9c5425049aef1bc7a812f890f00b5f79c7 (patch)
tree356e5fb2131ec63bff5c0467467bced5fabdf7cc /mm/rmap.c
parent3d0b95cd87b26b0b10e0cda8ee6105c2194a5800 (diff)
downloadlinux-54205e9c5425049aef1bc7a812f890f00b5f79c7.tar.xz
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 virtual–>physical mapping to a new value, since this allows us to properly handle systems whose caches are strict and require a virtual–>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@FVFYT0MHHV2J.usts.net/ Link: https://lkml.kernel.org/r/4f7ae6dfdc838ab71e1655188b657c032ff1f28f.1651056365.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mina Almasry <almasrymina@google.com> Cc: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
-rw-r--r--mm/rmap.c40
1 files changed, 22 insertions, 18 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 86ed2865210d..829b2f9486c6 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1532,15 +1532,16 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
* 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 folio *folio, struct vm_area_struct *vma,
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 folio *folio, struct vm_area_struct *vma,
* 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 folio *folio, struct vm_area_struct *vma,
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. */