hugetlb: fix resv_map leak in error path

hugetlb: fix resv_map leak in error path

When called for anonymous (non-shared) mappings, hugetlb_reserve_pages()
does a resv_map_alloc().  It depends on code in hugetlbfs's
vm_ops->close() to release that allocation.

However, in the mmap() failure path, we do a plain unmap_region() without
the remove_vma() which actually calls vm_ops->close().

This is a decent fix.  This leak could get reintroduced if new code (say,
after hugetlb_reserve_pages() in hugetlbfs_file_mmap()) decides to return
an error.  But, I think it would have to unroll the reservation anyway.

Christoph's test case:

	http://marc.info/?l=linux-mm&m=133728900729735

This patch applies to 3.4 and later.  A version for earlier kernels is at
https://lkml.org/lkml/2012/5/22/418.

Signed-off-by: Dave Hansen <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Acked-by: KOSAKI Motohiro <[email protected]>
Reported-by: Christoph Lameter <[email protected]>
Tested-by: Christoph Lameter <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: <[email protected]>	[2.6.32+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>