thp: run vma_adjust_trans_huge() outside i_mmap_rwsem

thp: run vma_adjust_trans_huge() outside i_mmap_rwsem

vma_addjust_trans_huge() splits pmd if it's crossing VMA boundary.
During split we munlock the huge page which requires rmap walk.  rmap
wants to take the lock on its own.

Let's move vma_adjust_trans_huge() outside i_mmap_rwsem to fix this.

Link: http://lkml.kernel.org/r/1466021202-61880-19-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Conflicts:
	mm/mmap.c

Orabug: 27026170

(cherry picked from commit 37f9f5595c26d3cb644ca2fab83dc4c4db119f9f)
Signed-off-by: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Reviewed-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>