[PATCH] freepgt: remove MM_VM_SIZE(mm)

There's only one usage of MM_VM_SIZE(mm) left, and it's a troublesome macro
because mm doesn't contain the (32-bit emulation?) info needed.  But it too is
only needed because we ignore the end from the vma list.

We could make flush_pgtables return that end, or unmap_vmas.  Choose the
latter, since it's a natural fit with unmap_mapping_range_vma needing to know
its restart addr.  This does make more than minimal change, but if unmap_vmas
had returned the end before, this is how we'd have done it, rather than
storing the break_addr in zap_details.

unmap_vmas used to return count of vmas scanned, but that's just debug which
hasn't been useful in a while; and if we want the map_count 0 on exit check
back, it can easily come from the final remove_vm_struct loop.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 16 insertions, 18 deletions

diff --git a/mm/memory.c b/mm/memory.c
index fee5dc8fc36c..854bd90eeca1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -645,7 +645,7 @@ static void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
  * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
  * @details: details of nonlinear truncation or shared cache invalidation
  *
- * Returns the number of vma's which were covered by the unmapping.
+ * Returns the end address of the unmapping (restart addr if interrupted).
  *
  * Unmap all pages in the vma list.  Called under page_table_lock.
  *
@@ -662,7 +662,7 @@ static void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
  * drops the lock and schedules.
  */
-int unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
+unsigned long unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
                 struct vm_area_struct *vma, unsigned long start_addr,
                 unsigned long end_addr, unsigned long *nr_accounted,
                 struct zap_details *details)
@@ -670,12 +670,11 @@ int unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
         unsigned long zap_bytes = ZAP_BLOCK_SIZE;
         unsigned long tlb_start = 0;    /* For tlb_finish_mmu */
         int tlb_start_valid = 0;
-        int ret = 0;
+        unsigned long start = start_addr;
         spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
         int fullmm = tlb_is_full_mm(*tlbp);
 
         for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
-                unsigned long start;
                 unsigned long end;
 
                 start = max(vma->vm_start, start_addr);
@@ -688,7 +687,6 @@ int unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
                 if (vma->vm_flags & VM_ACCOUNT)
                         *nr_accounted += (end - start) >> PAGE_SHIFT;
 
-                ret++;
                 while (start != end) {
                         unsigned long block;
 
@@ -719,7 +717,6 @@ int unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
                                 if (i_mmap_lock) {
                                         /* must reset count of rss freed */
                                         *tlbp = tlb_gather_mmu(mm, fullmm);
-                                        details->break_addr = start;
                                         goto out;
                                 }
                                 spin_unlock(&mm->page_table_lock);
@@ -733,7 +730,7 @@ int unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
                 }
         }
 out:
-        return ret;
+        return start;   /* which is now the end (or restart) address */
 }
 
 /**
@@ -743,7 +740,7 @@ out:
  * @size: number of bytes to zap
  * @details: details of nonlinear truncation or shared cache invalidation
  */
-void zap_page_range(struct vm_area_struct *vma, unsigned long address,
+unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
                 unsigned long size, struct zap_details *details)
 {
         struct mm_struct *mm = vma->vm_mm;
@@ -753,15 +750,16 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long address,
 
         if (is_vm_hugetlb_page(vma)) {
                 zap_hugepage_range(vma, address, size);
-                return;
+                return end;
         }
 
         lru_add_drain();
         spin_lock(&mm->page_table_lock);
         tlb = tlb_gather_mmu(mm, 0);
-        unmap_vmas(&tlb, mm, vma, address, end, &nr_accounted, details);
+        end = unmap_vmas(&tlb, mm, vma, address, end, &nr_accounted, details);
         tlb_finish_mmu(tlb, address, end);
         spin_unlock(&mm->page_table_lock);
+        return end;
 }
 
 /*
@@ -1348,7 +1346,7 @@ no_new_page:
  * i_mmap_lock.
  *
  * In order to make forward progress despite repeatedly restarting some
- * large vma, note the break_addr set by unmap_vmas when it breaks out:
+ * large vma, note the restart_addr from unmap_vmas when it breaks out:
  * and restart from that address when we reach that vma again.  It might
  * have been split or merged, shrunk or extended, but never shifted: so
  * restart_addr remains valid so long as it remains in the vma's range.
@@ -1386,8 +1384,8 @@ again:
                 }
         }
 
-        details->break_addr = end_addr;
-        zap_page_range(vma, start_addr, end_addr - start_addr, details);
+        restart_addr = zap_page_range(vma, start_addr,
+                                        end_addr - start_addr, details);
 
         /*
          * We cannot rely on the break test in unmap_vmas:
@@ -1398,14 +1396,14 @@ again:
         need_break = need_resched() ||
                         need_lockbreak(details->i_mmap_lock);
 
-        if (details->break_addr >= end_addr) {
+        if (restart_addr >= end_addr) {
                 /* We have now completed this vma: mark it so */
                 vma->vm_truncate_count = details->truncate_count;
                 if (!need_break)
                         return 0;
         } else {
                 /* Note restart_addr in vma's truncate_count field */
-                vma->vm_truncate_count = details->break_addr;
+                vma->vm_truncate_count = restart_addr;
                 if (!need_break)
                         goto again;
         }
diff --git a/mm/mmap.c b/mm/mmap.c
index 926d03015471..f8c61b2385ff 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1900,6 +1900,7 @@ void exit_mmap(struct mm_struct *mm)
         struct mmu_gather *tlb;
         struct vm_area_struct *vma = mm->mmap;
         unsigned long nr_accounted = 0;
+        unsigned long end;
 
         lru_add_drain();
 
@@ -1908,10 +1909,10 @@ void exit_mmap(struct mm_struct *mm)
         flush_cache_mm(mm);
         tlb = tlb_gather_mmu(mm, 1);
         /* Use -1 here to ensure all VMAs in the mm are unmapped */
-        mm->map_count -= unmap_vmas(&tlb, mm, vma, 0, -1, &nr_accounted, NULL);
+        end = unmap_vmas(&tlb, mm, vma, 0, -1, &nr_accounted, NULL);
         vm_unacct_memory(nr_accounted);
         free_pgtables(&tlb, vma, 0, 0);
-        tlb_finish_mmu(tlb, 0, MM_VM_SIZE(mm));
+        tlb_finish_mmu(tlb, 0, end);
 
         mm->mmap = mm->mmap_cache = NULL;
         mm->mm_rb = RB_ROOT;
@@ -1931,7 +1932,6 @@ void exit_mmap(struct mm_struct *mm)
                 vma = next;
         }
 
-        BUG_ON(mm->map_count);  /* This is just debugging */
         BUG_ON(mm->nr_ptes);    /* This is just debugging */
 }