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>