Some of the stats are 64bit and updation will be non atomic on 32bit
architecture. Use sequence counters on 32bit arch to make reading
of stats safe.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently we take blkg_stat lock for even updating the stats. So even if
a group has no throttling rules (common case for root group), we end
up taking blkg_lock, for updating the stats.

Make dispatch stats per cpu so that these can be updated without taking
blkg lock.

If cpu goes offline, these stats simply disappear. No protection has
been provided for that yet. Do we really need anything for that?
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

cgroup unaccounted_time file is created only if CONFIG_DEBUG_BLK_CGROUP=y.
there are some fields which are out side this config option. Fix that.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currentlly we first map the task to cgroup and then cgroup to
blkio_cgroup. There is a more direct way to get to blkio_cgroup
from task using task_subsys_state(). Use that.

The real reason for the fix is that it also avoids a race in generic
cgroup code. During remount/umount rebind_subsystems() is called and
it can do following with and rcu protection.

cgrp->subsys[i] = NULL;

That means if somebody got hold of cgroup under rcu and then it tried
to do cgroup->subsys[] to get to blkio_cgroup, it would get NULL which
is wrong. I was running into this race condition with ltp running on a
upstream derived kernel and that lead to crash.

So ideally we should also fix cgroup generic code to wait for rcu
grace period before setting pointer to NULL. Li Zefan is not very keen
on introducing synchronize_wait() as he thinks it will slow
down moun/remount/umount operations.

So for the time being atleast fix the kernel crash by taking a more
direct route to blkio_cgroup.

One tester had reported a crash while running LTP on a derived kernel
and with this fix crash is no more seen while the test has been
running for over 6 days.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Fixes generated by 'codespell' and manually reviewed.
Signed-off-by: NLucas De Marchi <lucas.demarchi@profusion.mobi>

This change moves unaccounted_time to only be reported when
CONFIG_DEBUG_BLK_CGROUP is true.
Signed-off-by: NJustin TerAvest <teravest@google.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

There are two kind of times that tasks are not charged for: the first
seek and the extra time slice used over the allocated timeslice. Both
of these exported as a new unaccounted_time stat.

I think it would be good to have this reported in 'time' as well, but
that is probably a separate discussion.
Signed-off-by: NJustin TerAvest <teravest@google.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

o Allow hierarchical cgroup creation for blkio controller

o Currently we disallow it as both the io controller policies (throttling
  as well as proportion bandwidth) do not support hierarhical accounting
  and control. But the flip side is that blkio controller can not be used with
  libvirt as libvirt creates a cgroup hierarchy deeper than 1 level.

  <top-level-cgroup-dir>/<controller>/libvirt/qemu/<virtual-machine-groups>

o So this patch will allow creation of cgroup hierarhcy but at the backend
  everything will be treated as flat. So if somebody created a an hierarchy
  like as follows.

			root
			/  \
		     test1 test2
			|
		     test3

  CFQ and throttling will practically treat all groups at same level.

				pivot
			     /  |   \  \
			root  test1 test2  test3

o Once we have actual support for hierarchical accounting and control
  then we can introduce another cgroup tunable file "blkio.use_hierarchy"
  which will be 0 by default but if user wants to enforce hierarhical
  control then it can be set to 1. This way there should not be any
  ABI problems down the line.

o The only not so pretty part is introduction of extra file "use_hierarchy"
  down the line. Kame-san had mentioned that hierarhical accounting is
  expensive in memory controller hence they keep it off by default. I
  suspect same will be the case for IO controller also as for each IO
  completion we shall have to account IO through hierarchy up to the root.
  if yes, then it probably is not a very bad idea to introduce this extra
  file so that it will be used only when somebody needs it and some people
  might enable hierarchy only in part of the hierarchy.

o This is how basically memory controller also uses "use_hierarhcy" and
  they also allowed creation of hierarchies when actual backend support
  was not available.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Acked-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
Reviewed-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Reviewed-by: NCiju Rajan K <ciju@linux.vnet.ibm.com>
Tested-by: NCiju Rajan K <ciju@linux.vnet.ibm.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

- Limit max iops value to UINT_MAX and return error to user if value is more
  than that instead of accepting bigger values and truncating implicitly.
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

o Currently any cgroup throttle limit changes are processed asynchronousy and
  the change does not take affect till a new bio is dispatched from same group.

o It might happen that a user sets a redicuously low limit on throttling.
  Say 1 bytes per second on reads. In such cases simple operations like mount
  a disk can wait for a very long time.

o Once bio is throttled, there is no easy way to come out of that wait even if
  user increases the read limit later.

o This patch fixes it. Now if a user changes the cgroup limits, we recalculate
  the bio dispatch time according to new limits.

o Can't take queueu lock under blkcg_lock, hence after the change I wake
  up the dispatch thread again which recalculates the time. So there are some
  variables being synchronized across two threads without lock and I had to
  make use of barriers. Hoping I have used barriers correctly. Any review of
  memory barrier code especially will help.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

o Now a cgroup list of blkg elements can contain blkg from multiple policies.
  Before sending an unlink event, make sure blkg belongs to they policy. If
  policy does not own the blkg, do not send update for this blkg.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently throttling related files were visible even if user had disabled
throttling using config options. It was switching off background throttling
of bio but not the cgroup files. This patch fixes it.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

o cgroup changes for IOPS throttling rules.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

o cgroup chagnes for throttle policy.

o Introduces READ and WRITE bytes per second throttling rules.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

o This patch prepares the base for introducing new IO control policies.
  Currently all the code is written knowing there is only one policy
  and that is proportional bandwidth. Creating infrastructure for newer
  policies to come in.

o Also there were many functions which were generated using macro. It was
  very confusing. Got rid of those.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

o Kill extra "dev weight" header which is printed when somebody reads
  blkio.weight_device file. This really seems to be out of convention. No other
  blkio files are printing any header at the start of file. I think it is ok
  to just print values and how to interpret values should be part of
  documentation.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

If the cgroup hierarchy for blkio control groups is deeper than two
levels, kernel should not allow the creation of further levels. mkdir
system call does not except EINVAL as a return value. This patch
replaces EINVAL with more appropriate EPERM
Signed-off-by: NCiju Rajan K <ciju@linux.vnet.ibm.com>
Reviewed-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

with CONFIG_PROVE_RCU=y, a warning can be triggered:

  # mount -t cgroup -o blkio xxx /mnt
  # mkdir /mnt/subgroup

...
kernel/cgroup.c:4442 invoked rcu_dereference_check() without protection!
...

To fix this, we avoid caling css_depth() here, which is a bit simpler
than the original code.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

goto has its place, but lets cut back on some of the more
frivolous uses of it.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This patch fixes few usability and configurability issues.

o All the cgroup based controller options are configurable from
  "Genral Setup/Control Group Support/" menu. blkio is the only exception.
  Hence make this option visible in above menu and make it configurable from
  there to bring it inline with rest of the cgroup based controllers.

o Get rid of CONFIG_DEBUG_CFQ_IOSCHED.

  This option currently does two things.

  - Enable printing of cgroup paths in blktrace
  - Enables CONFIG_DEBUG_BLK_CGROUP, which in turn displays additional stat
    files in cgroup.

  If we are using group scheduling, blktrace data is of not really much use
  if cgroup information is not present. To get this data, currently one has to
  also enable CONFIG_DEBUG_CFQ_IOSCHED, which in turn brings the overhead of
  all the additional debug stat files which is not desired.

  Hence, this patch moves printing of cgroup paths under
  CONFIG_CFQ_GROUP_IOSCHED.

  This allows us to get rid of CONFIG_DEBUG_CFQ_IOSCHED completely. Now all
  the debug stat files are controlled only by CONFIG_DEBUG_BLK_CGROUP which
  can be enabled through config menu.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Acked-by: NDivyesh Shah <dpshah@google.com>
Reviewed-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

o Once in a while, I was hitting a BUG_ON() in blkio code. empty_time was
  assuming that upon slice expiry, group can't be marked empty already (except
  forced dispatch).

  But this assumption is broken if cfqq can move (group_isolation=0) across
  groups after receiving a request.

  I think most likely in this case we got a request in a cfqq and accounted
  the rq in one group, later while adding the cfqq to tree, we moved the queue
  to a different group which was already marked empty and after dispatch from
  slice we found group already marked empty and raised alarm.

  This patch does not error out if group is already marked empty. This can
  introduce some empty_time stat error only in case of group_isolation=0. This
  is better than crashing. In case of group_isolation=1 we should still get
  same stats as before this patch.

[  222.308546] ------------[ cut here ]------------
[  222.309311] kernel BUG at block/blk-cgroup.c:236!
[  222.309311] invalid opcode: 0000 [#1] SMP
[  222.309311] last sysfs file: /sys/devices/virtual/block/dm-3/queue/scheduler
[  222.309311] CPU 1
[  222.309311] Modules linked in: dm_round_robin dm_multipath qla2xxx scsi_transport_fc dm_zero dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]
[  222.309311]
[  222.309311] Pid: 4780, comm: fio Not tainted 2.6.34-rc4-blkio-config #68 0A98h/HP xw8600 Workstation
[  222.309311] RIP: 0010:[<ffffffff8121ad88>]  [<ffffffff8121ad88>] blkiocg_set_start_empty_time+0x50/0x83
[  222.309311] RSP: 0018:ffff8800ba6e79f8  EFLAGS: 00010002
[  222.309311] RAX: 0000000000000082 RBX: ffff8800a13b7990 RCX: ffff8800a13b7808
[  222.309311] RDX: 0000000000002121 RSI: 0000000000000082 RDI: ffff8800a13b7a30
[  222.309311] RBP: ffff8800ba6e7a18 R08: 0000000000000000 R09: 0000000000000001
[  222.309311] R10: 000000000002f8c8 R11: ffff8800ba6e7ad8 R12: ffff8800a13b78ff
[  222.309311] R13: ffff8800a13b7990 R14: 0000000000000001 R15: ffff8800a13b7808
[  222.309311] FS:  00007f3beec476f0(0000) GS:ffff880001e40000(0000) knlGS:0000000000000000
[  222.309311] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  222.309311] CR2: 000000000040e7f0 CR3: 00000000a12d5000 CR4: 00000000000006e0
[  222.309311] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  222.309311] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[  222.309311] Process fio (pid: 4780, threadinfo ffff8800ba6e6000, task ffff8800b3d6bf00)
[  222.309311] Stack:
[  222.309311]  0000000000000001 ffff8800bab17a48 ffff8800bab17a48 ffff8800a13b7800
[  222.309311] <0> ffff8800ba6e7a68 ffffffff8121da35 ffff880000000001 00ff8800ba5c5698
[  222.309311] <0> ffff8800ba6e7a68 ffff8800a13b7800 0000000000000000 ffff8800bab17a48
[  222.309311] Call Trace:
[  222.309311]  [<ffffffff8121da35>] __cfq_slice_expired+0x2af/0x3ec
[  222.309311]  [<ffffffff8121fd7b>] cfq_dispatch_requests+0x2c8/0x8e8
[  222.309311]  [<ffffffff8120f1cd>] ? spin_unlock_irqrestore+0xe/0x10
[  222.309311]  [<ffffffff8120fb1a>] ? blk_insert_cloned_request+0x70/0x7b
[  222.309311]  [<ffffffff81210461>] blk_peek_request+0x191/0x1a7
[  222.309311]  [<ffffffffa0002799>] dm_request_fn+0x38/0x14c [dm_mod]
[  222.309311]  [<ffffffff810ae61f>] ? sync_page_killable+0x0/0x35
[  222.309311]  [<ffffffff81210fd4>] __generic_unplug_device+0x32/0x37
[  222.309311]  [<ffffffff81211274>] generic_unplug_device+0x2e/0x3c
[  222.309311]  [<ffffffffa00011a6>] dm_unplug_all+0x42/0x5b [dm_mod]
[  222.309311]  [<ffffffff8120ca37>] blk_unplug+0x29/0x2d
[  222.309311]  [<ffffffff8120ca4d>] blk_backing_dev_unplug+0x12/0x14
[  222.309311]  [<ffffffff81109a7a>] block_sync_page+0x35/0x39
[  222.309311]  [<ffffffff810ae616>] sync_page+0x41/0x4a
[  222.309311]  [<ffffffff810ae62d>] sync_page_killable+0xe/0x35
[  222.309311]  [<ffffffff8158aa59>] __wait_on_bit_lock+0x46/0x8f
[  222.309311]  [<ffffffff810ae4f5>] __lock_page_killable+0x66/0x6d
[  222.309311]  [<ffffffff81056f9c>] ? wake_bit_function+0x0/0x33
[  222.309311]  [<ffffffff810ae528>] lock_page_killable+0x2c/0x2e
[  222.309311]  [<ffffffff810afbc5>] generic_file_aio_read+0x361/0x4f0
[  222.309311]  [<ffffffff810ea044>] do_sync_read+0xcb/0x108
[  222.309311]  [<ffffffff811e42f7>] ? security_file_permission+0x16/0x18
[  222.309311]  [<ffffffff810ea6ab>] vfs_read+0xab/0x108
[  222.309311]  [<ffffffff810ea7c8>] sys_read+0x4a/0x6e
[  222.309311]  [<ffffffff81002b5b>] system_call_fastpath+0x16/0x1b
[  222.309311] Code: 58 01 00 00 00 48 89 c6 75 0a 48 83 bb 60 01 00 00 00 74 09 48 8d bb a0 00 00 00 eb 35 41 fe cc 74 0d f6 83 c0 01 00 00 04 74 04 <0f> 0b eb fe 48 89 75 e8 e8 be e0 de ff 66 83 8b c0 01 00 00 04
[  222.309311] RIP  [<ffffffff8121ad88>] blkiocg_set_start_empty_time+0x50/0x83
[  222.309311]  RSP <ffff8800ba6e79f8>
[  222.309311] ---[ end trace 32b4f71dffc15712 ]---
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Acked-by: NDivyesh Shah <dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This fixes the lockdep warning reported by Gui Jianfeng.
Signed-off-by: NDivyesh Shah <dpshah@google.com>
Reviewed-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Fixes compile errors in blk-cgroup code for empty_time stat and a merge fix in
CFQ. The first error was when CONFIG_DEBUG_CFQ_IOSCHED is not set.
Signed-off-by: NDivyesh Shah <dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Changelog from v1:
o Call blkiocg_update_idle_time_stats() at cfq_rq_enqueued() instead of at
  dispatch time.

Changelog from original patchset: (in response to Vivek Goyal's comments)
o group blkiocg_update_blkio_group_dequeue_stats() with other DEBUG functions
o rename blkiocg_update_set_active_queue_stats() to
  blkiocg_update_avg_queue_size_stats()
o s/request/io/ in blkiocg_update_request_add_stats() and
  blkiocg_update_request_remove_stats()
o Call cfq_del_timer() at request dispatch() instead of
  blkiocg_update_idle_time_stats()

Signed-off-by: Divyesh Shah<dpshah@google.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Currently, IO Controller makes use of blkio.weight to assign weight for
all devices. Here a new user interface "blkio.weight_device" is introduced to
assign different weights for different devices. blkio.weight becomes the
default value for devices which are not configured by "blkio.weight_device"

You can use the following format to assigned specific weight for a given
device:
#echo "major:minor weight" > blkio.weight_device

major:minor represents device number.

And you can remove weight for a given device as following:
#echo "major:minor 0" > blkio.weight_device

V1->V2 changes:
- use user interface "weight_device" instead of "policy" suggested by Vivek
- rename some struct suggested by Vivek
- rebase to 2.6-block "for-linus" branch
- remove an useless list_empty check pointed out by Li Zefan
- some trivial typo fix

V2->V3 changes:
- Move policy_*_node() functions up to get rid of forward declarations
- rename related functions by adding prefix "blkio_"
Signed-off-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

1) group_wait_time - This is the amount of time the cgroup had to wait to get a
  timeslice for one of its queues from when it became busy, i.e., went from 0
  to 1 request queued. This is different from the io_wait_time which is the
  cumulative total of the amount of time spent by each IO in that cgroup waiting
  in the scheduler queue. This stat is a great way to find out any jobs in the
  fleet that are being starved or waiting for longer than what is expected (due
  to an IO controller bug or any other issue).
2) empty_time - This is the amount of time a cgroup spends w/o any pending
   requests. This stat is useful when a job does not seem to be able to use its
   assigned disk share by helping check if that is happening due to an IO
   controller bug or because the job is not submitting enough IOs.
3) idle_time - This is the amount of time spent by the IO scheduler idling
   for a given cgroup in anticipation of a better request than the exising ones
   from other queues/cgroups.

All these stats are recorded using start and stop events. When reading these
stats, we do not add the delta between the current time and the last start time
if we're between the start and stop events. We avoid doing this to make sure
that these numbers are always monotonically increasing when read. Since we're
using sched_clock() which may use the tsc as its source, it may induce some
inconsistency (due to tsc resync across cpus) if we included the current delta.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

These stats are useful for getting a feel for the queue depth of the cgroup,
i.e., how filled up its queues are at a given instant and over the existence of
the cgroup. This ability is useful when debugging problems in the wild as it
helps understand the application's IO pattern w/o having to read through the
userspace code (coz its tedious or just not available) or w/o the ability
to run blktrace (since you may not have root access and/or not want to disturb
performance).

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This includes both the number of bios merged into requests belonging to this
cgroup as well as the number of requests merged together.
In the past, we've observed different merging behavior across upstream kernels,
some by design some actual bugs. This stat helps a lot in debugging such
problems when applications report decreased throughput with a new kernel
version.

This needed adding an extra elevator function to capture bios being merged as I
did not want to pollute elevator code with blkiocg knowledge and hence needed
the accounting invocation to come from CFQ.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

that include some minor fixes and addresses all comments.

Changelog: (most based on Vivek Goyal's comments)
o renamed blkiocg_reset_write to blkiocg_reset_stats
o more clarification in the documentation on io_service_time and io_wait_time
o Initialize blkg->stats_lock
o rename io_add_stat to blkio_add_stat and declare it static
o use bool for direction and sync
o derive direction and sync info from existing rq methods
o use 12 for major:minor string length
o define io_service_time better to cover the NCQ case
o add a separate reset_stats interface
o make the indexed stats a 2d array to simplify macro and function pointer code
o blkio.time now exports in jiffies as before
o Added stats description in patch description and
  Documentation/cgroup/blkio-controller.txt
o Prefix all stats functions with blkio and make them static as applicable
o replace IO_TYPE_MAX with IO_TYPE_TOTAL
o Moved #define constant to top of blk-cgroup.c
o Pass dev_t around instead of char *
o Add note to documentation file about resetting stats
o use BLK_CGROUP_MODULE in addition to BLK_CGROUP config option in #ifdef
  statements
o Avoid struct request specific knowledge in blk-cgroup. blk-cgroup.h now has
  rq_direction() and rq_sync() functions which are used by CFQ and when using
  io-controller at a higher level, bio_* functions can be added.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

We also add start_time_ns and io_start_time_ns fields to struct request
here to record the time when a request is created and when it is
dispatched to device. We use ns uints here as ms and jiffies are
not very useful for non-rotational media.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

- io_service_time
- io_wait_time
- io_serviced
- io_service_bytes

These stats are accumulated per operation type helping us to distinguish between
read and write, and sync and async IO. This patch does not increment any of
these stats.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

that info at request dispatch with other stats now. This patch removes the
existing support for accounting sectors for a blkio_group. This will be added
back differently in the next two patches.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: NTejun Heo <tj@kernel.org>
Guess-its-ok-by: NChristoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

Modify the Block I/O cgroup subsystem to be able to be built as a module.
As the CFQ disk scheduler optionally depends on blk-cgroup, config options
in block/Kconfig, block/Kconfig.iosched, and block/blk-cgroup.h are
enhanced to support the new module dependency.
Signed-off-by: NBen Blum <bblum@andrew.cmu.edu>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There's no need to take css reference here, for the caller
has already called rcu_read_lock() to prevent cgroup from
being removed.
Signed-off-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

I triggered a lockdep warning as following.

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.33-rc2 #1
-------------------------------------------------------
test_io_control/7357 is trying to acquire lock:
 (blkio_list_lock){+.+...}, at: [<c053a990>] blkiocg_weight_write+0x82/0x9e

but task is already holding lock:
 (&(&blkcg->lock)->rlock){......}, at: [<c053a949>] blkiocg_weight_write+0x3b/0x9e

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&(&blkcg->lock)->rlock){......}:
       [<c04583b7>] validate_chain+0x8bc/0xb9c
       [<c0458dba>] __lock_acquire+0x723/0x789
       [<c0458eb0>] lock_acquire+0x90/0xa7
       [<c0692b0a>] _raw_spin_lock_irqsave+0x27/0x5a
       [<c053a4e1>] blkiocg_add_blkio_group+0x1a/0x6d
       [<c053cac7>] cfq_get_queue+0x225/0x3de
       [<c053eec2>] cfq_set_request+0x217/0x42d
       [<c052c8a6>] elv_set_request+0x17/0x26
       [<c0532a0f>] get_request+0x203/0x2c5
       [<c0532ae9>] get_request_wait+0x18/0x10e
       [<c0533470>] __make_request+0x2ba/0x375
       [<c0531985>] generic_make_request+0x28d/0x30f
       [<c0532da7>] submit_bio+0x8a/0x8f
       [<c04d827a>] submit_bh+0xf0/0x10f
       [<c04d91d2>] ll_rw_block+0xc0/0xf9
       [<f86e9705>] ext3_find_entry+0x319/0x544 [ext3]
       [<f86eae58>] ext3_lookup+0x2c/0xb9 [ext3]
       [<c04c3e1b>] do_lookup+0xd3/0x172
       [<c04c56c8>] link_path_walk+0x5fb/0x95c
       [<c04c5a65>] path_walk+0x3c/0x81
       [<c04c5b63>] do_path_lookup+0x21/0x8a
       [<c04c66cc>] do_filp_open+0xf0/0x978
       [<c04c0c7e>] open_exec+0x1b/0xb7
       [<c04c1436>] do_execve+0xbb/0x266
       [<c04081a9>] sys_execve+0x24/0x4a
       [<c04028a2>] ptregs_execve+0x12/0x18

-> #1 (&(&q->__queue_lock)->rlock){..-.-.}:
       [<c04583b7>] validate_chain+0x8bc/0xb9c
       [<c0458dba>] __lock_acquire+0x723/0x789
       [<c0458eb0>] lock_acquire+0x90/0xa7
       [<c0692b0a>] _raw_spin_lock_irqsave+0x27/0x5a
       [<c053dd2a>] cfq_unlink_blkio_group+0x17/0x41
       [<c053a6eb>] blkiocg_destroy+0x72/0xc7
       [<c0467df0>] cgroup_diput+0x4a/0xb2
       [<c04ca473>] dentry_iput+0x93/0xb7
       [<c04ca4b3>] d_kill+0x1c/0x36
       [<c04cb5c5>] dput+0xf5/0xfe
       [<c04c6084>] do_rmdir+0x95/0xbe
       [<c04c60ec>] sys_rmdir+0x10/0x12
       [<c04027cc>] sysenter_do_call+0x12/0x32

-> #0 (blkio_list_lock){+.+...}:
       [<c0458117>] validate_chain+0x61c/0xb9c
       [<c0458dba>] __lock_acquire+0x723/0x789
       [<c0458eb0>] lock_acquire+0x90/0xa7
       [<c06929fd>] _raw_spin_lock+0x1e/0x4e
       [<c053a990>] blkiocg_weight_write+0x82/0x9e
       [<c0467f1e>] cgroup_file_write+0xc6/0x1c0
       [<c04bd2f3>] vfs_write+0x8c/0x116
       [<c04bd7c6>] sys_write+0x3b/0x60
       [<c04027cc>] sysenter_do_call+0x12/0x32

other info that might help us debug this:

1 lock held by test_io_control/7357:
 #0:  (&(&blkcg->lock)->rlock){......}, at: [<c053a949>] blkiocg_weight_write+0x3b/0x9e
stack backtrace:
Pid: 7357, comm: test_io_control Not tainted 2.6.33-rc2 #1
Call Trace:
 [<c045754f>] print_circular_bug+0x91/0x9d
 [<c0458117>] validate_chain+0x61c/0xb9c
 [<c0458dba>] __lock_acquire+0x723/0x789
 [<c0458eb0>] lock_acquire+0x90/0xa7
 [<c053a990>] ? blkiocg_weight_write+0x82/0x9e
 [<c06929fd>] _raw_spin_lock+0x1e/0x4e
 [<c053a990>] ? blkiocg_weight_write+0x82/0x9e
 [<c053a990>] blkiocg_weight_write+0x82/0x9e
 [<c0467f1e>] cgroup_file_write+0xc6/0x1c0
 [<c0454df5>] ? trace_hardirqs_off+0xb/0xd
 [<c044d93a>] ? cpu_clock+0x2e/0x44
 [<c050e6ec>] ? security_file_permission+0xf/0x11
 [<c04bcdda>] ? rw_verify_area+0x8a/0xad
 [<c0467e58>] ? cgroup_file_write+0x0/0x1c0
 [<c04bd2f3>] vfs_write+0x8c/0x116
 [<c04bd7c6>] sys_write+0x3b/0x60
 [<c04027cc>] sysenter_do_call+0x12/0x32

To prevent deadlock, we should take locks as following sequence:

blkio_list_lock -> queue_lock ->  blkcg_lock.

The following patch should fix this bug.
Signed-off-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

o One of the goals of block IO controller is that it should be able to
  support mulitple io control policies, some of which be operational at
  higher level in storage hierarchy.

o To begin with, we had one io controlling policy implemented by CFQ, and
  I hard coded the CFQ functions called by blkio. This created issues when
  CFQ is compiled as module.

o This patch implements a basic dynamic io controlling policy registration
  functionality in blkio. This is similar to elevator functionality where
  ioschedulers register the functions dynamically.

o Now in future, when more IO controlling policies are implemented, these
  can dynakically register with block IO controller.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

o blkio controller is inside the kernel and cfq makes use of interfaces
  exported by blkio. CFQ can be a module too, hence export symbols used
  by CFQ.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

They should not be declared inside some other file that's not related
to CFQ.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>