1 files changed, 35 insertions, 44 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 8d95902e9a38..214b6a258eeb 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -658,6 +658,9 @@ again:			remove_next = 1 + (end > next->vm_end);
         validate_mm(mm);
 }
 
+/* Flags that can be inherited from an existing mapping when merging */
+#define VM_MERGEABLE_FLAGS (VM_CAN_NONLINEAR)
+
 /*
  * If the vma has a ->close operation then the driver probably needs to release
  * per-vma resources, so we don't attempt to merge those.
@@ -665,7 +668,7 @@ again:			remove_next = 1 + (end > next->vm_end);
 static inline int is_mergeable_vma(struct vm_area_struct *vma,
                         struct file *file, unsigned long vm_flags)
 {
-        if (vma->vm_flags != vm_flags)
+        if ((vma->vm_flags ^ vm_flags) & ~VM_MERGEABLE_FLAGS)
                 return 0;
         if (vma->vm_file != file)
                 return 0;
@@ -1087,6 +1090,15 @@ int vma_wants_writenotify(struct vm_area_struct *vma)
                 mapping_cap_account_dirty(vma->vm_file->f_mapping);
 }
 
+/*
+ * We account for memory if it's a private writeable mapping,
+ * and VM_NORESERVE wasn't set.
+ */
+static inline int accountable_mapping(unsigned int vm_flags)
+{
+        return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
+}
+
 unsigned long mmap_region(struct file *file, unsigned long addr,
                           unsigned long len, unsigned long flags,
                           unsigned int vm_flags, unsigned long pgoff,
@@ -1114,36 +1126,32 @@ munmap_back:
         if (!may_expand_vm(mm, len >> PAGE_SHIFT))
                 return -ENOMEM;
 
-        if (flags & MAP_NORESERVE)
+        /*
+         * Set 'VM_NORESERVE' if we should not account for the
+         * memory use of this mapping. We only honor MAP_NORESERVE
+         * if we're allowed to overcommit memory.
+         */
+        if ((flags & MAP_NORESERVE) && sysctl_overcommit_memory != OVERCOMMIT_NEVER)
+                vm_flags |= VM_NORESERVE;
+        if (!accountable)
                 vm_flags |= VM_NORESERVE;
 
-        if (accountable && (!(flags & MAP_NORESERVE) ||
-                            sysctl_overcommit_memory == OVERCOMMIT_NEVER)) {
-                if (vm_flags & VM_SHARED) {
-                        /* Check memory availability in shmem_file_setup? */
-                        vm_flags |= VM_ACCOUNT;
-                } else if (vm_flags & VM_WRITE) {
-                        /*
-                         * Private writable mapping: check memory availability
-                         */
-                        charged = len >> PAGE_SHIFT;
-                        if (security_vm_enough_memory(charged))
-                                return -ENOMEM;
-                        vm_flags |= VM_ACCOUNT;
-                }
+        /*
+         * Private writable mapping: check memory availability
+         */
+        if (accountable_mapping(vm_flags)) {
+                charged = len >> PAGE_SHIFT;
+                if (security_vm_enough_memory(charged))
+                        return -ENOMEM;
+                vm_flags |= VM_ACCOUNT;
         }
 
         /*
-         * Can we just expand an old private anonymous mapping?
-         * The VM_SHARED test is necessary because shmem_zero_setup
-         * will create the file object for a shared anonymous map below.
+         * Can we just expand an old mapping?
          */
-        if (!file && !(vm_flags & VM_SHARED)) {
-                vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
-                                        NULL, NULL, pgoff, NULL);
-                if (vma)
-                        goto out;
-        }
+        vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
+        if (vma)
+                goto out;
 
         /*
          * Determine the object being mapped and call the appropriate
@@ -1186,14 +1194,6 @@ munmap_back:
                         goto free_vma;
         }
 
-        /* We set VM_ACCOUNT in a shared mapping's vm_flags, to inform
-         * shmem_zero_setup (perhaps called through /dev/zero's ->mmap)
-         * that memory reservation must be checked; but that reservation
-         * belongs to shared memory object, not to vma: so now clear it.
-         */
-        if ((vm_flags & (VM_SHARED|VM_ACCOUNT)) == (VM_SHARED|VM_ACCOUNT))
-                vma->vm_flags &= ~VM_ACCOUNT;
-
         /* Can addr have changed??
          *
          * Answer: Yes, several device drivers can do it in their
@@ -1206,17 +1206,8 @@ munmap_back:
         if (vma_wants_writenotify(vma))
                 vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
 
-        if (file && vma_merge(mm, prev, addr, vma->vm_end,
-                        vma->vm_flags, NULL, file, pgoff, vma_policy(vma))) {
-                mpol_put(vma_policy(vma));
-                kmem_cache_free(vm_area_cachep, vma);
-                fput(file);
-                if (vm_flags & VM_EXECUTABLE)
-                        removed_exe_file_vma(mm);
-        } else {
-                vma_link(mm, vma, prev, rb_link, rb_parent);
-                file = vma->vm_file;
-        }
+        vma_link(mm, vma, prev, rb_link, rb_parent);
+        file = vma->vm_file;
 
         /* Once vma denies write, undo our temporary denial count */
         if (correct_wcount)