From: David Miller Date: Mon, 8 Oct 2012 23:34:26 +0000 (-0700) Subject: mm: thp: Use more portable PMD clearing sequenece in zap_huge_pmd(). X-Git-Tag: v3.7-rc1~74^2~1 X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=f5c8ad47284ca01dafc37da5a72bb9644174d387;p=~emulex%2Finfiniband.git mm: thp: Use more portable PMD clearing sequenece in zap_huge_pmd(). 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 Cc: Andrea Arcangeli Cc: Johannes Weiner Cc: Gerald Schaefer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 68a3c93036f..a863af26c79 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1024,9 +1024,10 @@ 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);