thp: add tlb_remove_pmd_tlb_entry

We have tlb_remove_tlb_entry to indicate a pte tlb flush entry should be
flushed, but not a corresponding API for pmd entry.  This isn't a
problem so far because THP is only for x86 currently and tlb_flush()
under x86 will flush entire TLB.  But this is confusion and could be
missed if thp is ported to other arch.

Also convert tlb->need_flush = 1 to a VM_BUG_ON(!tlb->need_flush) in
__tlb_remove_page() as suggested by Andrea Arcangeli.  The
__tlb_remove_page() function is supposed to be called after
tlb_remove_xxx_tlb_entry() and we can catch any misuse.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 19 insertions, 4 deletions

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index e58fa777fa09..f96a5b58a975 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -139,6 +139,20 @@ static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
                 __tlb_remove_tlb_entry(tlb, ptep, address);     \
         } while (0)
 
+/**
+ * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation
+ * This is a nop so far, because only x86 needs it.
+ */
+#ifndef __tlb_remove_pmd_tlb_entry
+#define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0)
+#endif
+
+#define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)            \
+        do {                                                    \
+                tlb->need_flush = 1;                            \
+                __tlb_remove_pmd_tlb_entry(tlb, pmdp, address); \
+        } while (0)
+
 #define pte_free_tlb(tlb, ptep, address)                        \
         do {                                                    \
                 tlb->need_flush = 1;                            \
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a9ace9c32507..1b921299abc4 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -18,7 +18,7 @@ extern struct page *follow_trans_huge_pmd(struct mm_struct *mm,
                                           unsigned int flags);
 extern int zap_huge_pmd(struct mmu_gather *tlb,
                         struct vm_area_struct *vma,
-                        pmd_t *pmd);
+                        pmd_t *pmd, unsigned long addr);
 extern int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
                         unsigned long addr, unsigned long end,
                         unsigned char *vec);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 964fc5a2edd2..5a595554bd8c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1026,7 +1026,7 @@ out:
 }
 
 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
-                 pmd_t *pmd)
+                 pmd_t *pmd, unsigned long addr)
 {
         int ret = 0;
 
@@ -1042,6 +1042,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
                         pgtable = get_pmd_huge_pte(tlb->mm);
                         page = pmd_page(*pmd);
                         pmd_clear(pmd);
+                        tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
                         page_remove_rmap(page);
                         VM_BUG_ON(page_mapcount(page) < 0);
                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
diff --git a/mm/memory.c b/mm/memory.c
index 829d43735402..5e30583c2605 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -293,7 +293,7 @@ int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 {
         struct mmu_gather_batch *batch;
 
-        tlb->need_flush = 1;
+        VM_BUG_ON(!tlb->need_flush);
 
         if (tlb_fast_mode(tlb)) {
                 free_page_and_swap_cache(page);
@@ -1231,7 +1231,7 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
                         if (next-addr != HPAGE_PMD_SIZE) {
                                 VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem));
                                 split_huge_page_pmd(vma->vm_mm, pmd);
-                        } else if (zap_huge_pmd(tlb, vma, pmd))
+                        } else if (zap_huge_pmd(tlb, vma, pmd, addr))
                                 continue;
                         /* fall through */
                 }