nommu: fix a number of issues with the per-MM VMA patch

Fix a number of issues with the per-MM VMA patch:

 (1) Make mmap_pages_allocated an atomic_long_t, just in case this is used on
     a NOMMU system with more than 2G pages.  Makes no difference on a 32-bit
     system.

 (2) Report vma->vm_pgoff * PAGE_SIZE as a 64-bit value, not a 32-bit value,
     lest it overflow.

 (3) Move the allocation of the vm_area_struct slab back for fork.c.

 (4) Use KMEM_CACHE() for both vm_area_struct and vm_region slabs.

 (5) Use BUG_ON() rather than if () BUG().

 (6) Make the default validate_nommu_regions() a static inline rather than a
     #define.

 (7) Make free_page_series()'s objection to pages with a refcount != 1 more
     informative.

 (8) Adjust the __put_nommu_region() banner comment to indicate that the
     semaphore must be held for writing.

 (9) Limit the number of warnings about munmaps of non-mmapped regions.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 27 deletions

diff --git a/mm/nommu.c b/mm/nommu.c
index 2fcf47d449b4..72eda4aee2cb 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -69,7 +69,7 @@ int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
 int sysctl_nr_trim_pages = 1; /* page trimming behaviour */
 int heap_stack_gap = 0;
 
-atomic_t mmap_pages_allocated;
+atomic_long_t mmap_pages_allocated;
 
 EXPORT_SYMBOL(mem_map);
 EXPORT_SYMBOL(num_physpages);
@@ -463,12 +463,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
  */
 void __init mmap_init(void)
 {
-        vm_region_jar = kmem_cache_create("vm_region_jar",
-                                          sizeof(struct vm_region), 0,
-                                          SLAB_PANIC, NULL);
-        vm_area_cachep = kmem_cache_create("vm_area_struct",
-                                           sizeof(struct vm_area_struct), 0,
-                                           SLAB_PANIC, NULL);
+        vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC);
 }
 
 /*
@@ -486,27 +481,24 @@ static noinline void validate_nommu_regions(void)
                 return;
 
         last = rb_entry(lastp, struct vm_region, vm_rb);
-        if (unlikely(last->vm_end <= last->vm_start))
-                BUG();
-        if (unlikely(last->vm_top < last->vm_end))
-                BUG();
+        BUG_ON(unlikely(last->vm_end <= last->vm_start));
+        BUG_ON(unlikely(last->vm_top < last->vm_end));
 
         while ((p = rb_next(lastp))) {
                 region = rb_entry(p, struct vm_region, vm_rb);
                 last = rb_entry(lastp, struct vm_region, vm_rb);
 
-                if (unlikely(region->vm_end <= region->vm_start))
-                        BUG();
-                if (unlikely(region->vm_top < region->vm_end))
-                        BUG();
-                if (unlikely(region->vm_start < last->vm_top))
-                        BUG();
+                BUG_ON(unlikely(region->vm_end <= region->vm_start));
+                BUG_ON(unlikely(region->vm_top < region->vm_end));
+                BUG_ON(unlikely(region->vm_start < last->vm_top));
 
                 lastp = p;
         }
 }
 #else
-#define validate_nommu_regions() do {} while(0)
+static void validate_nommu_regions(void)
+{
+}
 #endif
 
 /*
@@ -563,16 +555,17 @@ static void free_page_series(unsigned long from, unsigned long to)
                 struct page *page = virt_to_page(from);
 
                 kdebug("- free %lx", from);
-                atomic_dec(&mmap_pages_allocated);
+                atomic_long_dec(&mmap_pages_allocated);
                 if (page_count(page) != 1)
-                        kdebug("free page %p [%d]", page, page_count(page));
+                        kdebug("free page %p: refcount not one: %d",
+                               page, page_count(page));
                 put_page(page);
         }
 }
 
 /*
  * release a reference to a region
- * - the caller must hold the region semaphore, which this releases
+ * - the caller must hold the region semaphore for writing, which this releases
  * - the region may not have been added to the tree yet, in which case vm_top
  *   will equal vm_start
  */
@@ -1096,7 +1089,7 @@ static int do_mmap_private(struct vm_area_struct *vma,
                 goto enomem;
 
         total = 1 << order;
-        atomic_add(total, &mmap_pages_allocated);
+        atomic_long_add(total, &mmap_pages_allocated);
 
         point = rlen >> PAGE_SHIFT;
 
@@ -1107,7 +1100,7 @@ static int do_mmap_private(struct vm_area_struct *vma,
                         order = ilog2(total - point);
                         n = 1 << order;
                         kdebug("shave %lu/%lu @%lu", n, total - point, total);
-                        atomic_sub(n, &mmap_pages_allocated);
+                        atomic_long_sub(n, &mmap_pages_allocated);
                         total -= n;
                         set_page_refcounted(pages + total);
                         __free_pages(pages + total, order);
@@ -1536,10 +1529,15 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
         /* find the first potentially overlapping VMA */
         vma = find_vma(mm, start);
         if (!vma) {
-                printk(KERN_WARNING
-                       "munmap of memory not mmapped by process %d (%s):"
-                       " 0x%lx-0x%lx\n",
-                       current->pid, current->comm, start, start + len - 1);
+                static int limit = 0;
+                if (limit < 5) {
+                        printk(KERN_WARNING
+                               "munmap of memory not mmapped by process %d"
+                               " (%s): 0x%lx-0x%lx\n",
+                               current->pid, current->comm,
+                               start, start + len - 1);
+                        limit++;
+                }
                 return -EINVAL;
         }