[PATCH] statm: __vm_stat_accounting

The procfs shared_vm accounting in do_mmap_pgoff didn't balance with munmap
in the case of shared anonymous: because file comes in NULL, whereas
vm_file gets set at the end by shmem_zero_setup.

Update file; and update vm_flags (a driver is likely to add VM_IO or
VM_RESERVED, modifying reserved_vm); and update pgoff (doesn't affect
procfs accounting, but could affect vma_merge - though at present all
drivers which modify vm_pgoff set a VM_SPECIAL which prevents merging). 
And do that __vm_stat_account before advancing to make_pages_present.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: William Irwin <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/mmap.c

@@ -988,9 +988,12 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
 	 *         f_op->mmap method. -DaveM
 	 */
 	addr = vma->vm_start;
+	pgoff = vma->vm_pgoff;
+	vm_flags = vma->vm_flags;
 
 	if (!file || !vma_merge(mm, prev, addr, vma->vm_end,
 			vma->vm_flags, NULL, file, pgoff, vma_policy(vma))) {
+		file = vma->vm_file;
 		vma_link(mm, vma, prev, rb_link, rb_parent);
 		if (correct_wcount)
 			atomic_inc(&inode->i_writecount);
@@ -1005,6 +1008,7 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
 	}
 out:	
 	mm->total_vm += len >> PAGE_SHIFT;
+	__vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
 	if (vm_flags & VM_LOCKED) {
 		mm->locked_vm += len >> PAGE_SHIFT;
 		make_pages_present(addr, addr + len);
@@ -1015,7 +1019,6 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
 					pgoff, flags & MAP_NONBLOCK);
 		down_write(&mm->mmap_sem);
 	}
-	__vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
 	return addr;
 
 unmap_and_free_vma: