mm: convert remove_migration_pte() to use page_vma_mapped_walk()

remove_migration_pte() also can easily be converted to
page_vma_mapped_walk().

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170129173858.45174-13-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 41 insertions, 61 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 6807174e0715..2c63ac06791b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -193,82 +193,62 @@ void putback_movable_pages(struct list_head *l)
 /*
  * Restore a potential migration pte to a working pte entry
  */
-static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
+static int remove_migration_pte(struct page *page, struct vm_area_struct *vma,
                                  unsigned long addr, void *old)
 {
-        struct mm_struct *mm = vma->vm_mm;
+        struct page_vma_mapped_walk pvmw = {
+                .page = old,
+                .vma = vma,
+                .address = addr,
+                .flags = PVMW_SYNC | PVMW_MIGRATION,
+        };
+        struct page *new;
+        pte_t pte;
         swp_entry_t entry;
-        pmd_t *pmd;
-        pte_t *ptep, pte;
-        spinlock_t *ptl;
 
-        if (unlikely(PageHuge(new))) {
-                ptep = huge_pte_offset(mm, addr);
-                if (!ptep)
-                        goto out;
-                ptl = huge_pte_lockptr(hstate_vma(vma), mm, ptep);
-        } else {
-                pmd = mm_find_pmd(mm, addr);
-                if (!pmd)
-                        goto out;
+        VM_BUG_ON_PAGE(PageTail(page), page);
+        while (page_vma_mapped_walk(&pvmw)) {
+                new = page - pvmw.page->index +
+                        linear_page_index(vma, pvmw.address);
 
-                ptep = pte_offset_map(pmd, addr);
+                get_page(new);
+                pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
+                if (pte_swp_soft_dirty(*pvmw.pte))
+                        pte = pte_mksoft_dirty(pte);
 
                 /*
-                 * Peek to check is_swap_pte() before taking ptlock?  No, we
-                 * can race mremap's move_ptes(), which skips anon_vma lock.
+                 * Recheck VMA as permissions can change since migration started
                  */
-
-                ptl = pte_lockptr(mm, pmd);
-        }
-
-        spin_lock(ptl);
-        pte = *ptep;
-        if (!is_swap_pte(pte))
-                goto unlock;
-
-        entry = pte_to_swp_entry(pte);
-
-        if (!is_migration_entry(entry) ||
-            migration_entry_to_page(entry) != old)
-                goto unlock;
-
-        get_page(new);
-        pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot)));
-        if (pte_swp_soft_dirty(*ptep))
-                pte = pte_mksoft_dirty(pte);
-
-        /* Recheck VMA as permissions can change since migration started  */
-        if (is_write_migration_entry(entry))
-                pte = maybe_mkwrite(pte, vma);
+                entry = pte_to_swp_entry(*pvmw.pte);
+                if (is_write_migration_entry(entry))
+                        pte = maybe_mkwrite(pte, vma);
 
 #ifdef CONFIG_HUGETLB_PAGE
-        if (PageHuge(new)) {
-                pte = pte_mkhuge(pte);
-                pte = arch_make_huge_pte(pte, vma, new, 0);
-        }
+                if (PageHuge(new)) {
+                        pte = pte_mkhuge(pte);
+                        pte = arch_make_huge_pte(pte, vma, new, 0);
+                }
 #endif
-        flush_dcache_page(new);
-        set_pte_at(mm, addr, ptep, pte);
+                flush_dcache_page(new);
+                set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
 
-        if (PageHuge(new)) {
-                if (PageAnon(new))
-                        hugepage_add_anon_rmap(new, vma, addr);
+                if (PageHuge(new)) {
+                        if (PageAnon(new))
+                                hugepage_add_anon_rmap(new, vma, pvmw.address);
+                        else
+                                page_dup_rmap(new, true);
+                } else if (PageAnon(new))
+                        page_add_anon_rmap(new, vma, pvmw.address, false);
                 else
-                        page_dup_rmap(new, true);
-        } else if (PageAnon(new))
-                page_add_anon_rmap(new, vma, addr, false);
-        else
-                page_add_file_rmap(new, false);
+                        page_add_file_rmap(new, false);
 
-        if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
-                mlock_vma_page(new);
+                if (vma->vm_flags & VM_LOCKED && !PageTransCompound(new))
+                        mlock_vma_page(new);
+
+                /* No need to invalidate - it was non-present before */
+                update_mmu_cache(vma, pvmw.address, pvmw.pte);
+        }
 
-        /* No need to invalidate - it was non-present before */
-        update_mmu_cache(vma, addr, ptep);
-unlock:
-        pte_unmap_unlock(ptep, ptl);
-out:
         return SWAP_AGAIN;
 }