[PATCHSET] block: per-queue policy activation, take#2

[Tejun Heo]

Hello,

Upto now, blkcg assumed that all policies are active on all queues
which simply isn't true - cfq policy is only applicable to queues
which are using cfq as the elevator.  Also, for transition purposes,
the current implementation clears all !root blkgs blkgs across
elevator switch and policy [de]registration in racy manner.

This patchset implements per-queue policy activation.  Static policy
ID is replaced with dynamic registration and each policy should be
activated and deactivated explicitly on each queue.  On activation,
the matching policy data are created on all existing blkgs.  On
deactivation, the matching policy data are removed from all existing
blkgs.  blkg printing skips blkg-policy combination which is disabled
and trying to configure a policy on a blkg which doesn't have the
policy enabled would return -EINVAL instead of creating an unused
dummy configuration.

Changes from the last take[L] are

* 0001 to fix config dependent build error / warnings added.

* More comments added to 0006 as suggested by Vivek.

* 0007 added to avoid boot time bypass delays.

* 0009 made cfq_init_queue() return garbage after alloc failure if
  !CONFIG_CFQ_GROUP_IOSCHED.  Fixed.

* 0011 which shoots down all blkgs if no policy is activated added.
  Suggested by Vivek.

 0001-cfq-fix-build-breakage-warnings.patch
 0002-blkcg-kill-blkio_list-and-replace-blkio_list_lock-wi.patch
 0003-blkcg-use-pol-instead-of-plid-in-update_root_blkg_pd.patch
 0004-blkcg-remove-static-policy-ID-enums.patch
 0005-blkcg-make-blkg_conf_prep-take-pol-and-return-with-q.patch
 0006-blkcg-make-sure-blkg_lookup-returns-NULL-if-q-is-byp.patch
 0007-blkcg-make-request_queue-bypassing-on-allocation.patch
 0008-blkcg-add-request_queue-root_blkg.patch
 0009-blkcg-implement-per-queue-policy-activation.patch
 0010-blkcg-drop-stuff-unused-after-per-queue-policy-activ.patch
 0011-blkcg-shoot-down-blkgs-if-all-policies-are-deactivat.patch

This patchset is on top of the current block/for-3.5/core 5bc4afb1ec
"blkcg: drop BLKCG_STAT_{PRIV|POL|OFF} macros" and also available in
the following git branch.

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git blkcg-pols

diffstat follows.

 block/blk-cgroup.c     |  424 ++++++++++++++++++++++++++++++-------------------
 block/blk-cgroup.h     |   43 ++--
 block/blk-core.c       |    4 
 block/blk-throttle.c   |   78 +++------
 block/cfq-iosched.c    |   71 ++++----
 block/elevator.c       |    2 
 include/linux/blkdev.h |   10 +
 7 files changed, 367 insertions(+), 265 deletions(-)

Thanks.

--
tejun

[L] http://thread.gmane.org/gmane.linux.kernel.cgroups/1641