thp: mprotect: transparent huge page support

Natively handle huge pmds when changing page tables on behalf of
mprotect().

I left out update_mmu_cache() because we do not need it on x86 anyway but
more importantly the interface works on ptes, not pmds.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 25125fb..c590b08 100644 (file)
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -22,6 +22,8 @@ extern int zap_huge_pmd(struct mmu_gather *tlb,
 extern int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
                        unsigned long addr, unsigned long end,
                        unsigned char *vec);
+extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+                       unsigned long addr, pgprot_t newprot);
 
 enum transparent_hugepage_flag {
        TRANSPARENT_HUGEPAGE_FLAG,

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 37e89a3..7b55fe0 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -948,6 +948,33 @@ int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
        return ret;
 }
 
+int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+               unsigned long addr, pgprot_t newprot)
+{
+       struct mm_struct *mm = vma->vm_mm;
+       int ret = 0;
+
+       spin_lock(&mm->page_table_lock);
+       if (likely(pmd_trans_huge(*pmd))) {
+               if (unlikely(pmd_trans_splitting(*pmd))) {
+                       spin_unlock(&mm->page_table_lock);
+                       wait_split_huge_page(vma->anon_vma, pmd);
+               } else {
+                       pmd_t entry;
+
+                       entry = pmdp_get_and_clear(mm, addr, pmd);
+                       entry = pmd_modify(entry, newprot);
+                       set_pmd_at(mm, addr, pmd, entry);
+                       spin_unlock(&vma->vm_mm->page_table_lock);
+                       flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
+                       ret = 1;
+               }
+       } else
+               spin_unlock(&vma->vm_mm->page_table_lock);
+
+       return ret;
+}
+
 pmd_t *page_check_address_pmd(struct page *page,
                              struct mm_struct *mm,
                              unsigned long address,

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 9402080..5a688a2 100644 (file)
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -88,7 +88,13 @@ static inline void change_pmd_range(struct vm_area_struct *vma, pud_t *pud,
        pmd = pmd_offset(pud, addr);
        do {
                next = pmd_addr_end(addr, end);
-               split_huge_page_pmd(vma->vm_mm, pmd);
+               if (pmd_trans_huge(*pmd)) {
+                       if (next - addr != HPAGE_PMD_SIZE)
+                               split_huge_page_pmd(vma->vm_mm, pmd);
+                       else if (change_huge_pmd(vma, pmd, addr, newprot))
+                               continue;
+                       /* fall through */
+               }
                if (pmd_none_or_clear_bad(pmd))
                        continue;
                change_pte_range(vma->vm_mm, pmd, addr, next, newprot,