ia64: perfmon: don't mark buffer pages as PG_reserved

ia64: perfmon: don't mark buffer pages as PG_reserved

In the old days, remap_pfn_range() required pages to be marked as
PG_reserved, so they would e.g.  never get swapped out.  This was
required for special mappings.  Nowadays, this is fully handled via the
VMA (VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP inside
remap_pfn_range() to be precise).  PG_reserved is no longer required but
only a relic from the past.

So only architecture specific MM handling might require it (e.g.  to
detect them as MMIO pages).  As there are no architecture specific
checks for PageReserved() apart from MCA handling in ia64code, this can
go.  Use simple vzalloc()/vfree() instead.

Note that before calling vzalloc(), size has already been aligned to
PAGE_SIZE, no need to align again.

Link: http://lkml.kernel.org/r/20190114125903.24845-9-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>