mm/hugetlb: vma_has_reserves() needs to handle fallocate hole punch

mm/hugetlb: vma_has_reserves() needs to handle fallocate hole punch

Orabug: 21652814

In vma_has_reserves(), the current assumption is that reserves are always
present for shared mappings.  However, this will not be the case with
fallocate hole punch.  When punching a hole, the present page will be
deleted as well as the region/reserve map entry (and hence any
reservation).  vma_has_reserves is passed "chg" which indicates whether or
not a region/reserve map is present.  Use this to determine if reserves
are actually present or were removed via hole punch.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 320fb799e7cedc1edb96fd69c686547c731d5fc8)
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>