SUNRPC: Fix memory corruption issue on 32-bit highmem systems

Some architectures, such as ARM-32 do not return the same base address
when you call kmap_atomic() twice on the same page.
This causes problems for the memmove() call in the XDR helper routine
"_shift_data_right_pages()", since it defeats the detection of
overlapping memory ranges, and has been seen to corrupt memory.

The fix is to distinguish between the case where we're doing an
inter-page copy or not. In the former case of we know that the memory
ranges cannot possibly overlap, so we can additionally micro-optimise
by replacing memmove() with memcpy().

Reported-by: Mark Young <MYoung@nvidia.com>
Reported-by: Matt Craighead <mcraighead@nvidia.com>
Cc: Bruce Fields <bfields@fieldses.org>
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: Matt Craighead <mcraighead@nvidia.com>
workqueue: cond_resched() after processing each work item

If !PREEMPT, a kworker running work items back to back can hog CPU.
This becomes dangerous when a self-requeueing work item which is
waiting for something to happen races against stop_machine.  Such
self-requeueing work item would requeue itself indefinitely hogging
the kworker and CPU it's running on while stop_machine would wait for
that CPU to enter stop_machine while preventing anything else from
happening on all other CPUs.  The two would deadlock.

Jamie Liu reports that this deadlock scenario exists around
scsi_requeue_run_queue() and libata port multiplier support, where one
port may exclude command processing from other ports.  With the right
timing, scsi_requeue_run_queue() can end up requeueing itself trying
to execute an IO which is asked to be retried while another device has
an exclusive access, which in turn can't make forward progress due to
stop_machine.

Fix it by invoking cond_resched() after executing each work item.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jamie Liu <jamieliu@google.com>
References: http://thread.gmane.org/gmane.linux.kernel/1552567
Cc: stable@vger.kernel.org
--
 kernel/workqueue.c |    9 +++++++++
 1 file changed, 9 insertions(+)
cgroup: fix rmdir EBUSY regression in 3.11

On 3.11-rc we are seeing cgroup directories left behind when they should
have been removed.  Here's a trivial reproducer:

cd /sys/fs/cgroup/memory
mkdir parent parent/child; rmdir parent/child parent
rmdir: failed to remove `parent': Device or resource busy

It's because cgroup_destroy_locked() (step 1 of destruction) leaves
cgroup on parent's children list, letting cgroup_offline_fn() (step 2 of
destruction) remove it; but step 2 is run by work queue, which may not
yet have removed the children when parent destruction checks the list.

Fix that by checking through a non-empty list of children: if every one
of them has already been marked CGRP_DEAD, then it's safe to proceed:
those children are invisible to userspace, and should not obstruct rmdir.

(I didn't see any reason to keep the cgrp->children checks under the
unrelated css_set_lock, so moved them out.)

tj: Flattened nested ifs a bit and updated comment so that it's
    correct on both for-3.11-fixes and for-3.12.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Merge tag 'nfs-for-3.11-5' of git://git.linux-nfs.org/projects/trondmy/linux-nfs

Pull NFS client bugfix from Trond Myklebust:
 "Stable patch to fix a highmem-related data corruption issue on 32-bit
  ARM platforms"

* tag 'nfs-for-3.11-5' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  SUNRPC: Fix memory corruption issue on 32-bit highmem systems
Merge branch 'for-3.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Pull workqueue fix from Tejun Heo:
 "This contains one fix which could lead to system-wide lockup on
  !PREEMPT kernels.  It's very late in the cycle but this definitely is
  a -stable material.

  The problem is that workqueue worker tasks may process unlimited
  number of work items back-to-back without every yielding inbetween.
  This usually isn't noticeable but a work item which re-queues itself
  waiting for someone else to do something can deadlock with
  stop_machine.  stop_machine will ensure nothing else happens on all
  other cpus and the requeueing work item will reqeueue itself
  indefinitely without ever yielding and thus preventing the CPU from
  entering stop_machine.

  Kudos to Jamie Liu for spotting and diagnosing the problem.  This can
  be trivially fixed by adding cond_resched() after processing each work
  item"

* 'for-3.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: cond_resched() after processing each work item
Merge branch 'for-3.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fix from Tejun Heo:
 "During the percpu reference counting update which was merged during
  v3.11-rc1, the cgroup destruction path was updated so that a cgroup in
  the process of dying may linger on the children list, which was
  necessary as the cgroup should still be included in child/descendant
  iteration while percpu ref is being killed.

  Unfortunately, I forgot to update cgroup destruction path accordingly
  and cgroup destruction may fail spuriously with -EBUSY due to
  lingering dying children even when there's no live child left - e.g.
  "rmdir parent/child parent" will usually fail.

  This can be easily fixed by iterating through the children list to
  verify that there's no live child left.  While this is very late in
  the release cycle, this bug is very visible to userland and I believe
  the fix is relatively safe.

  Thanks Hugh for spotting and providing fix for the issue"

* 'for-3.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: fix rmdir EBUSY regression in 3.11