LINARO 2013.06 GCC 4.7.4 Update.
Added Pagasusq CPU GOV to INTELIHOTPLUG exclusion.

Now pegasusq gov will use it's own hotplug code.
BLOCK: Updated BFQ to V6R2 for 3.9.y kernel.
block: replace icq->changed with icq->flags

icq->changed was used for ICQ_*_CHANGED bits.  Rename it to flags and
access it under ioc->lock instead of using atomic bitops.
ioc_get_changed() is added so that the changed part can be fetched and
cleared as before.

icq->flags will be used to carry other flags.

Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: simplify ioc_release_fn()

Reverse double lock dancing in ioc_release_fn() can be simplified by
just using trylock on the queue_lock and back out from ioc lock on
trylock failure.  Simplify it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: exit_io_context() should call elevator_exit_icq_fn()

While updating locking, b2efa05265 "block, cfq: unlink
cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation
from exit_io_context() to the final ioc put.  While this doesn't cause
catastrophic failure, it effectively removes task exit notification to
elevator and cause noticeable IO performance degradation with CFQ.

On task exit, CFQ used to immediately expire the slice if it was being
used by the exiting task as no more IO would be issued by the task;
however, after b2efa05265, the notification is lost and disk could sit
idle needlessly, leading to noticeable IO performance degradation for
certain workloads.

This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates
elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it
from exit_io_context().  ICQ_EXITED flag is added to avoid invoking
the callback more than once for the same icq.

Walking icq_list from ioc side and invoking elevator callback requires
reverse double locking.  This may be better implemented using RCU;
unfortunately, using RCU isn't trivial.  e.g. RCU protection would
need to cover request_queue and queue_lock switch on cleanup makes
grabbing queue_lock from RCU unsafe.  Reverse double locking should
do, at least for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-bisected-by: Shaohua Li <shli@kernel.org>
LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com>
Tested-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: ioc_task_link() can't fail

ioc_task_link() is used to share %current's ioc on clone.  If
%current->io_context is set, %current is guaranteed to have refcount
on the ioc and, thus, ioc_task_link() can't fail.

Replace error checking in ioc_task_link() with WARN_ON_ONCE() and make
it just increment refcount and nr_tasks.

-v2: Description typo fix (Vivek).

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: add io_context->active_ref

Currently ioc->nr_tasks is used to decide two things - whether an ioc
is done issuing IOs and whether it's shared by multiple tasks.  This
patch separate out the first into ioc->active_ref, which is acquired
and released using {get|put}_io_context_active() respectively.

This will be used to associate bio's with a given task.  This patch
doesn't introduce any visible behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Small Fix to mach tree code for block/blk-ioc.c
elevator: clear auxiliary data earlier during elevator switch

Elevator switch tries hard to keep as much as context until new
elevator is ready so that it can revert to the original state if
initializing the new elevator fails for some reason.  Unfortunately,
with more auxiliary contexts to manage, this makes elevator init and
exit paths too complex and fragile.

This patch makes elevator_switch() unregister the current elevator and
flush icq's before start initializing the new one.  As we still keep
the old elevator itself, the only difference is that we lose icq's on
rare occassions of switching failure, which isn't critical at all.

Note that this makes explicit elevator parameter to
elevator_init_queue() and __elv_register_queue() unnecessary as they
always can use the current elevator.

This patch enables block cgroup cleanups.

-v2: blk_add_trace_msg() prints elevator name from @new_e instead of
     @e->type as the local variable no longer exists.  This caused
     build failure on CONFIG_BLK_DEV_IO_TRACE.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
elevator: make elevator_init_fn() return 0/-errno

elevator_ops->elevator_init_fn() has a weird return value.  It returns
a void * which the caller should assign to q->elevator->elevator_data
and %NULL return denotes init failure.

Update such that it returns integer 0/-errno and sets elevator_data
directly as necessary.

This makes the interface more conventional and eases further cleanup.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: implement blk_queue_bypass_start/end()

Rename and extend elv_queisce_start/end() to
blk_queue_bypass_start/end() which are exported and supports nesting
via @q->bypass_depth.  Also add blk_queue_bypass() to test bypass
state.

This will be further extended and used for blkio_group management.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg: shoot down blkio_groups on elevator switch

Elevator switch may involve changes to blkcg policies.  Implement
shoot down of blkio_groups.

Combined with the previous bypass updates, the end goal is updating
blkcg core such that it can ensure that blkcg's being affected become
quiescent and don't have any per-blkg data hanging around before
commencing any policy updates.  Until queues are made aware of the
policies that applies to them, as an interim step, all per-policy blkg
data will be shot down.

* blk-throtl doesn't need this change as it can't be disabled for a
  live queue; however, update it anyway as the scheduled blkg
  unification requires this behavior change.  This means that
  blk-throtl configuration will be unnecessarily lost over elevator
  switch.  This oddity will be removed after blkcg learns to associate
  individual policies with request_queues.

* blk-throtl dosen't shoot down root_tg.  This is to ease transition.
  Unified blkg will always have persistent root group and not shooting
  down root_tg for now eases transition to that point by avoiding
  having to update td->root_tg and is safe as blk-throtl can never be
  disabled

-v2: Vivek pointed out that group list is not guaranteed to be empty
     on return from clear function if it raced cgroup removal and
     lost.  Fix it by waiting a bit and retrying.  This kludge will
     soon be removed once locking is updated such that blkg is never
     in limbo state between blkcg and request_queue locks.

     blk-throtl no longer shoots down root_tg to avoid breaking
     td->root_tg.

     Also, Nest queue_lock inside blkio_list_lock not the other way
     around to avoid introduce possible deadlock via blkcg lock.

-v3: blkcg_clear_queue() repositioned and renamed to
     blkg_destroy_all() to increase consistency with later changes.
     cfq_clear_queue() updated to check q->elevator before
     dereferencing it to avoid NULL dereference on not fully
     initialized queues (used by later change).

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
cfq: don't register propio policy if !CONFIG_CFQ_GROUP_IOSCHED

cfq has been registering zeroed blkio_poilcy_cfq if CFQ_GROUP_IOSCHED
is disabled.  This fortunately doesn't collide with blk-throtl as
BLKIO_POLICY_PROP is zero but is unnecessary and risky.  Just don't
register it if not enabled.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg: move rcu_read_lock() outside of blkio_group get functions

rcu_read_lock() in throtl_get_tb() and cfq_get_cfqg() holds onto
@blkcg while looking up blkg.  For API cleanup, the next patch will
make the caller responsible for determining @blkcg to look blkg from
and let them specify it as a parameter.  Move rcu read locking out to
the callers to prepare for the change.

-v2: Originally this patch was described as a fix for RCU read locking
     bug around @blkg, which Vivek pointed out to be incorrect.  It
     was from misunderstanding the role of rcu locking as protecting
     @blkg not @blkcg.  Patch description updated.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg: update blkg get functions take blkio_cgroup as parameter

In both blkg get functions - throtl_get_tg() and cfq_get_cfqg(),
instead of obtaining blkcg of %current explicitly, let the caller
specify the blkcg to use as parameter and make both functions hold on
to the blkcg.

This is part of block cgroup interface cleanup and will help making
blkcg API more modular.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg: use q and plid instead of opaque void * for blkio_group association

blkgio_group is association between a block cgroup and a queue for a
given policy.  Using opaque void * for association makes things
confusing and hinders factoring of common code.  Use request_queue *
and, if necessary, policy id instead.

This will help block cgroup API cleanup.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg: use the usual get blkg path for root blkio_group

For root blkg, blk_throtl_init() was using throtl_alloc_tg()
explicitly and cfq_init_queue() was manually initializing embedded
cfqd->root_group, adding unnecessarily different code paths to blkg
handling.

Make both use the usual blkio_group get functions - throtl_get_tg()
and cfq_get_cfqg() - for the root blkio_group too.  Note that
blk_throtl_init() callsite is pushed downwards in
blk_alloc_queue_node() so that @q is sufficiently initialized for
throtl_get_tg().

This simplifies root blkg handling noticeably for cfq and will allow
further modularization of blkcg API.

-v2: Vivek pointed out that using cfq_get_cfqg() won't work if
     CONFIG_CFQ_GROUP_IOSCHED is disabled.  Fix it by factoring out
     initialization of base part of cfqg into cfq_init_cfqg_base() and
     alloc/init/free explicitly if !CONFIG_CFQ_GROUP_IOSCHED.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg: factor out blkio_group creation

Currently both blk-throttle and cfq-iosched implement their own
blkio_group creation code in throtl_get_tg() and cfq_get_cfqg().  This
patch factors out the common code into blkg_lookup_create(), which
returns ERR_PTR value so that transitional failures due to queue
bypass can be distinguished from other failures.

* New plkio_policy_ops methods blkio_alloc_group_fn() and
  blkio_link_group_fn added.  Both are transitional and will be
  removed once the blkg management code is fully moved into
  blk-cgroup.c.

* blkio_alloc_group_fn() allocates policy-specific blkg which is
  usually a larger data structure with blkg as the first entry and
  intiailizes it.  Note that initialization of blkg proper, including
  percpu stats, is responsibility of blk-cgroup proper.

  Note that default config (weight, bps...) initialization is done
  from this method; otherwise, we end up violating locking order
  between blkcg and q locks via blkcg_get_CONF() functions.

* blkio_link_group_fn() is called under queue_lock and responsible for
  linking the blkg to the queue.  blkcg side is handled by blk-cgroup
  proper.

* The common blkg creation function is named blkg_lookup_create() and
  blkiocg_lookup_group() is renamed to blkg_lookup() for consistency.
  Also, throtl / cfq related functions are similarly [re]named for
  consistency.

This simplifies blkcg policy implementations and enables further
cleanup.

-v2: Vivek noticed that blkg_lookup_create() incorrectly tested
     blk_queue_dead() instead of blk_queue_bypass() leading a user of
     the function ending up creating a new blkg on bypassing queue.
     This is a bug introduced while relocating bypass patches before
     this one.  Fixed.

-v3: ERR_PTR patch folded into this one.  @for_root added to
     blkg_lookup_create() to allow creating root group on a bypassed
     queue during elevator switch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg: don't allow or retain configuration of missing devices

blkcg is very peculiar in that it allows setting and remembering
configurations for non-existent devices by maintaining separate data
structures for configuration.

This behavior is completely out of the usual norms and outright
confusing; furthermore, it uses dev_t number to match the
configuration to devices, which is unpredictable to begin with and
becomes completely unuseable if EXT_DEVT is fully used.

It is wholely unnecessary - we already have fully functional userland
mechanism to program devices being hotplugged which has full access to
device identification, connection topology and filesystem information.

Add a new struct blkio_group_conf which contains all blkcg
configurations to blkio_group and let blkio_group, which can be
created iff the associated device exists and is removed when the
associated device goes away, carry all configurations.

Note that, after this patch, all newly created blkg's will always have
the default configuration (unlimited for throttling and blkcg's weight
for propio).

This patch makes blkio_policy_node meaningless but doesn't remove it.
The next patch will.

-v2: Updated to retry after short sleep if blkg lookup/creation failed
     due to the queue being temporarily bypassed as indicated by
     -EBUSY return.  Pointed out by Vivek.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>