procfs: disable per-task stack usage on NOMMU

It needs walk_page_range().

Reported-by: Michal Simek <monstr@monstr.eu>
Tested-by: Michal Simek <monstr@monstr.eu>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: David Howells <dhowells@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/array.c

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 0c6bc60..07f77a7 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -322,6 +322,8 @@
 			p->nivcsw);
 }
 
+#ifdef CONFIG_MMU
+
 struct stack_stats {
 	struct vm_area_struct *vma;
 	unsigned long	startpage;
@@ -402,6 +404,11 @@
 		mmput(mm);
 	}
 }
+#else
+static void task_show_stack_usage(struct seq_file *m, struct task_struct *task)
+{
+}
+#endif		/* CONFIG_MMU */
 
 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 			struct pid *pid, struct task_struct *task)

mm/Makefile

diff --git a/mm/Makefile b/mm/Makefile
index 515fd79..ebf8490 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -5,14 +5,14 @@
 mmu-y			:= nommu.o
 mmu-$(CONFIG_MMU)	:= fremap.o highmem.o madvise.o memory.o mincore.o \
 			   mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
-			   vmalloc.o
+			   vmalloc.o pagewalk.o
 
 obj-y			:= bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
 			   maccess.o page_alloc.o page-writeback.o \
 			   readahead.o swap.o truncate.o vmscan.o shmem.o \
 			   prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
 			   page_isolation.o mm_init.o mmu_context.o \
-			   pagewalk.o $(mmu-y)
+			   $(mmu-y)
 obj-y += init-mm.o
 
 obj-$(CONFIG_BOUNCE)	+= bounce.o