hugetlb: fix copy_hugetlb_page_range() to handle migration/hwpoisoned entry

commit 4a705fef986231a3e7a6b1a6d3c37025f021f49f upstream.

There's a race between fork() and hugepage migration, as a result we try
to "dereference" a swap entry as a normal pte, causing kernel panic.
The cause of the problem is that copy_hugetlb_page_range() can't handle
"swap entry" family (migration entry and hwpoisoned entry) so let's fix
it.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: <stable@vger.kernel.org>	[2.6.37+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mm: hugetlb: fix copy_hugetlb_page_range()

commit 0253d634e0803a8376a0d88efee0bf523d8673f9 upstream.

Commit 4a705fef9862 ("hugetlb: fix copy_hugetlb_page_range() to handle
migration/hwpoisoned entry") changed the order of
huge_ptep_set_wrprotect() and huge_ptep_get(), which leads to breakage
in some workloads like hugepage-backed heap allocation via libhugetlbfs.
This patch fixes it.

The test program for the problem is shown below:

  $ cat heap.c
  #include <unistd.h>
  #include <stdlib.h>
  #include <string.h>

  #define HPS 0x200000

  int main() {
  	int i;
  	char *p = malloc(HPS);
  	memset(p, '1', HPS);
  	for (i = 0; i < 5; i++) {
  		if (!fork()) {
  			memset(p, '2', HPS);
  			p = malloc(HPS);
  			memset(p, '3', HPS);
  			free(p);
  			return 0;
  		}
  	}
  	sleep(1);
  	free(p);
  	return 0;
  }

  $ export HUGETLB_MORECORE=yes ; export HUGETLB_NO_PREFAULT= ; hugectl --heap ./heap

Fixes 4a705fef9862 ("hugetlb: fix copy_hugetlb_page_range() to handle
migration/hwpoisoned entry"), so is applicable to -stable kernels which
include it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: Guillaume Morin <guillaume@morinfr.org>
Suggested-by: Guillaume Morin <guillaume@morinfr.org>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Revert "arm: autosmp: remove get/put_online_cpus"

This reverts commit c4fef841419109dab978b12e93b7087872879099.
arm: autosmp: use __read_mostly with enabled
Thanks to @moddingg33k
Also clean up trailing spaces
sched: fix race between try_to_wake_up() and move_task()

Until a task's state has been seen as interruptible/uninterruptible
and it is no longer on_cpu, it is possible that the task may move
to another CPU (load balancing may cause this). Here is an example
where the race condition results in incorrect operation:

- cpu 0 calls put_prev_task on task A, task A's state is TASK_RUNNING
- cpu 0 runs task B, which attempts to wake up A
- cpu 0 begins try_to_wake_up(), recording src_cpu for task A as cpu 0
- cpu 1 then pulls task A (perhaps due to idle balance)
- cpu 1 runs task A, which then sleeps, becoming INTERRUPTIBLE
- cpu 0 continues in try_to_wake_up(), thinking task A's previous
  cpu is 0, where it is actually 1
- if select_task_rq returns cpu 0, task A will be woken up on cpu 0
  without properly updating its cpu to 0 in set_task_cpu()

CRs-Fixed: 665958
Change-Id: Icee004cb320bd8edfc772d9f74e670a9d4978a99
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
Merge remote-tracking branch 'upstream/master'