Revert "Block : Squash update to V6r2 from Devil Kernel"

This reverts commit 66de26a9e0cc6c5ebcaf39f688bfd8eff8a9dede.
Revert "block: introduce the BFQ-v5 I/O sched for 3.3"

This reverts commit b541512c60062af29e5913b14ea64c83c15c72e7.
Revert "block: cgroups, kconfig, build bits for BFQ-v5-3.3"

This reverts commit 8f685bedfec85a790562022b40e0ff00170e0b51.

Conflicts:
	block/Kconfig.iosched
	include/linux/cgroup_subsys.h
Revert "block: do not notify urgent request, when flush with data in flight"

This reverts commit 90fb490b6236852f1f80749399f6b07e89cb0791.
Revert "block: allow REQ_PM requests even when the device is suspended"

This reverts commit be14ebcfb923204b264e8a4e09cc355b93ec53c2.
Revert "blkpm: avoid sleep when holding queue lock"

This reverts commit 71297c76e2b5b7b179590e8b82c46c30e8d2e9aa.
Revert "block: implement runtime pm strategy"

This reverts commit 12ac9e36721999178c94bdacb01769d3851303e4.
Revert "block: add runtime pm helpers"

This reverts commit e4b0e079b72749cbee7b8e557412fd6f4b6f8ce0.
Revert "block: add a flag to identify PM request"

This reverts commit ace058dd4ab9d84073301789b8ae4b0003320c8e.
Revert "block: bigass squash of upstream commits"

This reverts commit 353f3f95f4f4d764e05df3d7eff568d6369cd655.
block: prepare I/O context code for BFQ-v7r2 for 3.0

BFQ uses struct cfq_io_context to store its per-process per-device data,
reusing the same code for cic handling of CFQ.  The code is not shared
ATM to minimize the impact of these patches.

This patch introduces a new hlist to each io_context to store all the
cic's allocated by BFQ to allow calling the right destructor on module
unload; the radix tree used for cic lookup needs to be duplicated
because it can contain dead keys inserted by a scheduler and later
retrieved by the other one.

Update the io_context exit and free paths to take care also of
the BFQ cic's.

Change the type of cfqq inside struct cfq_io_context to void *
to use it also for BFQ per-queue data.

A new bfq-specific ioprio_changed field is necessary, too, to avoid
clobbering cfq's one, so switch ioprio_changed to a bitmap, with one
element per scheduler.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>

Conflicts:
	block/Kconfig.iosched
block: cgroups, kconfig, build bits for BFQ-v7r3-3.0

Add a Kconfig option and do the related Makefile changes to compile
the BFQ I/O scheduler.  Also add the bfqio controller to the cgroups
subsystem.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>

Conflicts:
	block/Makefile
	include/linux/cgroup_subsys.h
block: introduce the BFQ-v7r3 I/O sched for 3.0

Add the BFQ-v7r3 I/O scheduler to 3.0.
The general structure is borrowed from CFQ, as much code. A (bfq_)queue is
associated to each task doing I/O on a device, and each time a scheduling
decision has to be made a queue is selected and served until it expires.

    - Slices are given in the service domain: tasks are assigned budgets,
      measured in number of sectors. Once got the disk, a task must
      however consume its assigned budget within a configurable maximum time
      (by default, the maximum possible value of the budgets is automatically
      computed to comply with this timeout). This allows the desired latency
      vs "throughput boosting" tradeoff to be set.

    - Budgets are scheduled according to a variant of WF2Q+, implemented
      using an augmented rb-tree to take eligibility into account while
      preserving an O(log N) overall complexity.

    - A low-latency tunable is provided; if enabled, both interactive and soft
      real-time applications are guaranteed very low latency.

    - Latency guarantees are preserved also in presence of NCQ.

    - Also with flash-based devices, a high throughput is achieved while
      still preserving latency guarantees.

    - Useful features borrowed from CFQ: cooperating-queues merging (with
      some additional optimizations with respect to the original CFQ version),
      static fallback queue for OOM.

    - BFQ supports full hierarchical scheduling, exporting a cgroups
      interface.  Each node has a full scheduler, so each group can
      be assigned its own ioprio (mapped to a weight, see next point)
      and an ioprio_class.

    - If the cgroups interface is used, weights can be explictly assigned,
      otherwise ioprio values are mapped to weights using the relation
      weight = IOPRIO_BE_NR - ioprio.

    - ioprio classes are served in strict priority order, i.e., lower
      priority queues are not served as long as there are higher priority
      queues.  Among queues in the same class the bandwidth is distributed
      in proportion to the weight of each queue. A very thin extra bandwidth
      is however guaranteed to the Idle class, to prevent it from starving.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
block, bfq: add Early Queue Merge (EQM) to BFQ-v7r3 for 3.0.0

A set of processes may happen  to  perform interleaved reads, i.e., requests
whose union would give rise to a  sequential read  pattern.  There are two
typical  cases: in the first  case,   processes  read  fixed-size chunks of
data at a fixed distance from each other, while in the second case processes
may read variable-size chunks at  variable distances. The latter case occurs
for  example with  KVM, which  splits the  I/O generated  by the  guest into
multiple chunks,  and lets these chunks  be served by a  pool of cooperating
processes,  iteratively  assigning  the  next  chunk of  I/O  to  the first
available  process. CFQ  uses actual  queue merging  for the  first type of
rocesses, whereas it  uses preemption to get a sequential  read pattern out
of the read requests  performed by the second type of  processes. In the end
it uses  two different  mechanisms to  achieve the  same goal: boosting the
throughput with interleaved I/O.

This patch introduces  Early Queue Merge (EQM), a unified mechanism to get a
sequential  read pattern  with both  types of  processes. The  main idea is
checking newly arrived requests against the next request of the active queue
both in case of actual request insert and in case of request merge. By doing
so, both the types of processes can be handled by just merging their queues.
EQM is  then simpler and  more compact than the  pair of mechanisms used in
CFQ.

Finally, EQM  also preserves the  typical low-latency properties of BFQ, by
properly restoring the weight-raising state of  a queue when it gets back to
a non-merged state.

Signed-off-by: Mauro Andreolini <mauro.andreolini@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Reviewed-by: Paolo Valente <paolo.valente@unimore.it>