procfs: call default get_unmapped_area on MMU-present architectures
procfs: call default get_unmapped_area on MMU-present architectures

Commit c4fe24485729 ("sparc: fix PCI device proc file mmap(2)") added
proc_reg_get_unmapped_area in proc_reg_file_ops and
proc_reg_file_ops_no_compat, by which now mmap always returns EIO if
get_unmapped_area method is not defined for the target procfs file,
which causes regression of mmap on /proc/vmcore.

To address this issue, like get_unmapped_area(), call default
current->mm->get_unmapped_area on MMU-present architectures if
pde->proc_fops->get_unmapped_area, i.e.  the one in actual file
operation in the procfs file, is not defined.

Reported-by: Michael Holzheu <db4757c56f54651f568cc7cda79cd93c781b1605@linux.vnet.ibm.com>
Signed-off-by: HATAYAMA Daisuke <e293c7e13ecc029aa287dca4b8ecfdf8a10ea3b9@jp.fujitsu.com>
Cc: Alexey Dobriyan <b99bff5923d24d2fb8e844db9dac7cd59203da1d@gmail.com>
Cc: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>
Tested-by: Michael Holzheu <db4757c56f54651f568cc7cda79cd93c781b1605@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs