[PATCHSET v2 block/for-4.3] block, cgroup: make cfq charge async IOs to the appropriate blkcgs

[Tejun Heo]

Hello,

This is v2 of cfq cgroup writeback patchset.  Changes from the last
take[L] are

* Switched from GFP_ATOMIC to GFP_NOWAIT as suggested by Jeff.

* Other misc review points addressed, acks added and rebased.

cfq has always charged all async IOs to the root cgroup.  It didn't
have much choice as writeback didn't know about cgroups and there was
no way to tell who to blame for a given writeback IO.  writeback
finally grew support for cgroups and now tags each writeback IO with
the appropriate cgroup to charge it against.

This patchset updates cfq so that it follows the blkcg each bio is
tagged with.  Async cfq_queues are now shared across cfq_group, which
is per-cgroup, instead of per-request_queue cfq_data.  This makes all
IOs follow the weight based IO resource distribution implemented by
cfq.

This patchset contains the following 8 patches.

 0001-cfq-iosched-simplify-control-flow-in-cfq_get_queue.patch
 0002-cfq-iosched-fix-async-oom-queue-handling.patch
 0003-cfq-iosched-fix-oom-cfq_queue-ref-leak-in-cfq_set_re.patch
 0004-cfq-iosched-minor-cleanups.patch
 0005-blkcg-cfq-iosched-use-GFP_NOWAIT-instead-of-GFP_ATOM.patch
 0006-cfq-iosched-remove-gfp_mask-from-cfq_find_alloc_queu.patch
 0007-cfq-iosched-move-cfq_group-determination-from-cfq_fi.patch
 0008-cfq-iosched-fold-cfq_find_alloc_queue-into-cfq_get_q.patch
 0009-cfq-iosched-charge-async-IOs-to-the-appropriate-blkc.patch

0001-0003 are a prep and two fix patches on top.  The bugs fixed by
these patches are very unlikely to cause problems in actual usage, so
the patches aren't tagged w/ -stable.

0004-0008 are prep patches.

0009 makes cfq cgroup-writeback ready.

This patchset is on top of

  d770e558e219 ("Linux 4.2-rc1")
+ [1] [PATCHSET block/for-4.3] writeback: cgroup writeback updates

diffstat follows, thanks.

 block/blk-cgroup.c  |    8 -
 block/cfq-iosched.c |  220 ++++++++++++++++++++--------------------------------
 2 files changed, 89 insertions(+), 139 deletions(-)

--
tejun

[L] http://lkml.kernel.org/g/1433753973-23684-1-git-send-email-tj@xxxxxxxxxx
[1] http://lkml.kernel.org/g/1436281823-1947-1-git-send-email-tj@xxxxxxxxxx
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