[PATCH] percpu data: only iterate over possible CPUs

percpu_data blindly allocates bootmem memory to store NR_CPUS instances of
cpudata, instead of allocating memory only for possible cpus.

As a preparation for changing that, we need to convert various 0 -> NR_CPUS
loops to use for_each_cpu().

(The above only applies to users of asm-generic/percpu.h.  powerpc has gone it
alone and is presently only allocating memory for present CPUs, so it's
currently corrupting memory).

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Jens Axboe <axboe@suse.de>
Cc: Anton Blanchard <anton@samba.org>
Acked-by: William Irwin <wli@holomorphy.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 44b4eb4202d9..dde04ff4be31 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1213,18 +1213,21 @@ static void __get_page_state(struct page_state *ret, int nr, cpumask_t *cpumask)
 {
         int cpu = 0;
 
-        memset(ret, 0, sizeof(*ret));
+        memset(ret, 0, nr * sizeof(unsigned long));
         cpus_and(*cpumask, *cpumask, cpu_online_map);
 
         cpu = first_cpu(*cpumask);
         while (cpu < NR_CPUS) {
                 unsigned long *in, *out, off;
 
+                if (!cpu_isset(cpu, *cpumask))
+                        continue;
+
                 in = (unsigned long *)&per_cpu(page_states, cpu);
 
                 cpu = next_cpu(cpu, *cpumask);
 
-                if (cpu < NR_CPUS)
+                if (likely(cpu < NR_CPUS))
                         prefetch(&per_cpu(page_states, cpu));
 
                 out = (unsigned long *)ret;
@@ -1886,8 +1889,7 @@ static void setup_pagelist_highmark(struct per_cpu_pageset *p,
  * not check if the processor is online before following the pageset pointer.
  * Other parts of the kernel may not check if the zone is available.
  */
-static struct per_cpu_pageset
-        boot_pageset[NR_CPUS];
+static struct per_cpu_pageset boot_pageset[NR_CPUS];
 
 /*
  * Dynamically allocate memory for the