Invalidation sequences are handled in various ways on various
architectures.
One way, which sparc64 uses, is to let the set_*_at() functions
accumulate pending flushes into a per-cpu array. Then the
flush_tlb_range() et al. calls process the pending TLB flushes.
In this regime, the __tlb_remove_*tlb_entry() implementations are
essentially NOPs.
The canonical PTE zap in mm/memory.c is:
ptent = ptep_get_and_clear_full(mm, addr, pte,
tlb->fullmm);
tlb_remove_tlb_entry(tlb, pte, addr);
With a subsequent tlb_flush_mmu() if needed.
Mirror this in the THP PMD zapping using:
orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
page = pmd_page(orig_pmd);
tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
And we properly accomodate TLB flush mechanims like the one described
above.
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
---
mm/huge_memory.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 20eeb2b..2fa0c59 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -996,9 +996,10 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
if (__pmd_trans_huge_lock(pmd, vma) == 1) {
struct page *page;
pgtable_t pgtable;
+ pmd_t orig_pmd;
pgtable = pgtable_trans_huge_withdraw(tlb->mm);
- page = pmd_page(*pmd);
- pmd_clear(pmd);
+ orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
+ page = pmd_page(orig_pmd);
tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
page_remove_rmap(page);
VM_BUG_ON(page_mapcount(page) < 0);
--
1.7.10.4
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