Hello,
So, this patch should do. Joe, Vivek, can one of you guys please
verify that the oops goes away with this patch?
Jens, the original thread can be read at
http://thread.gmane.org/gmane.linux.kernel/1720729
The fix converts blkg->refcnt from int to atomic_t. It does some
overhead but it should be minute compared to everything else which is
going on and the involved cacheline bouncing, so I think it's highly
unlikely to cause any noticeable difference. Also, the refcnt in
question should be converted to a perpcu_ref for blk-mq anyway, so the
atomic_t is likely to go away pretty soon anyway.
Thanks.
------- 8< -------
__blkg_release_rcu() may be invoked after the associated request_queue
is released with a RCU grace period inbetween. As such, the function
and callbacks invoked from it must not dereference the associated
request_queue. This is clearly indicated in the comment above the
function.
Unfortunately, while trying to fix a different issue, 2a4fd070ee
("blkcg: move bulk of blkcg_gq release operations to the RCU
callback") ignored this and added [un]locking of @blkg->q->queue_lock
to __blkg_release_rcu(). This of course can cause oops as the
request_queue may be long gone by the time this code gets executed.
general protection fault: 0000 [#1] SMP
CPU: 21 PID: 30 Comm: rcuos/21 Not tainted 3.15.0 #1
Hardware name: Stratus ftServer 6400/G7LAZ, BIOS BIOS Version 6.3:57 12/25/2013
task: ffff880854021de0 ti: ffff88085403c000 task.ti: ffff88085403c000
RIP: 0010:[<ffffffff8162e9e5>] [<ffffffff8162e9e5>] _raw_spin_lock_irq+0x15/0x60
RSP: 0018:ffff88085403fdf0 EFLAGS: 00010086
RAX: 0000000000020000 RBX: 0000000000000010 RCX: 0000000000000000
RDX: 000060ef80008248 RSI: 0000000000000286 RDI: 6b6b6b6b6b6b6b6b
RBP: ffff88085403fdf0 R08: 0000000000000286 R09: 0000000000009f39
R10: 0000000000020001 R11: 0000000000020001 R12: ffff88103c17a130
R13: ffff88103c17a080 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88107fca0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006e5ab8 CR3: 000000000193d000 CR4: 00000000000407e0
Stack:
ffff88085403fe18 ffffffff812cbfc2 ffff88103c17a130 0000000000000000
ffff88103c17a130 ffff88085403fec0 ffffffff810d1d28 ffff880854021de0
ffff880854021de0 ffff88107fcaec58 ffff88085403fe80 ffff88107fcaec30
Call Trace:
[<ffffffff812cbfc2>] __blkg_release_rcu+0x72/0x150
[<ffffffff810d1d28>] rcu_nocb_kthread+0x1e8/0x300
[<ffffffff81091d81>] kthread+0xe1/0x100
[<ffffffff8163813c>] ret_from_fork+0x7c/0xb0
Code: ff 47 04 48 8b 7d 08 be 00 02 00 00 e8 55 48 a4 ff 5d c3 0f 1f 00 66 66 66 66 90 55 48 89 e5
+fa 66 66 90 66 66 90 b8 00 00 02 00 <f0> 0f c1 07 89 c2 c1 ea 10 66 39 c2 75 02 5d c3 83 e2 fe 0f
+b7
RIP [<ffffffff8162e9e5>] _raw_spin_lock_irq+0x15/0x60
RSP <ffff88085403fdf0>
The request_queue locking was added because blkcg_gq->refcnt is an int
protected with the queue lock and __blkg_release_rcu() needs to put
the parent. Let's fix it by making blkcg_gq->refcnt an atomic_t and
dropping queue locking in the function.
Given the general heavy weight of the current request_queue and blkcg
operations, this is unlikely to cause any noticeable overhead.
Moreover, blkcg_gq->refcnt is likely to be converted to percpu_ref in
the near future, so whatever (most likely negligible) overhead it may
add is temporary.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Joe Lawrence <joe.lawrence@stratus.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Link: http://lkml.kernel.org/g/alpine.DEB.2.02.1406081816540.17948@jlaw-desktop.mno.stratus.com
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>
Pull block layer fixes from Jens Axboe:
"Final small batch of fixes to be included before -rc1. Some general
cleanups in here as well, but some of the blk-mq fixes we need for the
NVMe conversion and/or scsi-mq. The pull request contains:
- Support for not merging across a specified "chunk size", if set by
the driver. Some NVMe devices perform poorly for IO that crosses
such a chunk, so we need to support it generically as part of
request merging avoid having to do complicated split logic. From
me.
- Bump max tag depth to 10Ki tags. Some scsi devices have a huge
shared tag space. Before we failed with EINVAL if a too large tag
depth was specified, now we truncate it and pass back the actual
value. From me.
- Various blk-mq rq init fixes from me and others.
- A fix for enter on a dying queue for blk-mq from Keith. This is
needed to prevent oopsing on hot device removal.
- Fixup for blk-mq timer addition from Ming Lei.
- Small round of performance fixes for mtip32xx from Sam Bradshaw.
- Minor stack leak fix from Rickard Strandqvist.
- Two __init annotations from Fabian Frederick"
* 'for-linus' of git://git.kernel.dk/linux-block:
block: add __init to blkcg_policy_register
block: add __init to elv_register
block: ensure that bio_add_page() always accepts a page for an empty bio
blk-mq: add timer in blk_mq_start_request
blk-mq: always initialize request->start_time
block: blk-exec.c: Cleaning up local variable address returnd
mtip32xx: minor performance enhancements
blk-mq: ->timeout should be cleared in blk_mq_rq_ctx_init()
blk-mq: don't allow queue entering for a dying queue
blk-mq: bump max tag depth to 10K tags
block: add blk_rq_set_block_pc()
block: add notion of a chunk size for request merging
blkcg_policy_register is only called by
__init functions:
__init cfq_init
__init throtl_init
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jens Axboe <axboe@fb.com>
cgroup in general is moving towards using cgroup_subsys_state as the
fundamental structural component and css_parent() was introduced to
convert from using cgroup->parent to css->parent. It was quite some
time ago and we're moving forward with making css more prominent.
This patch drops the trivial wrapper css_parent() and let the users
dereference css->parent. While at it, explicitly mark fields of css
which are public and immutable.
v2: New usage from device_cgroup.c converted.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Pull cgroup updates from Tejun Heo:
"A lot updates for cgroup:
- The biggest one is cgroup's conversion to kernfs. cgroup took
after the long abandoned vfs-entangled sysfs implementation and
made it even more convoluted over time. cgroup's internal objects
were fused with vfs objects which also brought in vfs locking and
object lifetime rules. Naturally, there are places where vfs rules
don't fit and nasty hacks, such as credential switching or lock
dance interleaving inode mutex and cgroup_mutex with object serial
number comparison thrown in to decide whether the operation is
actually necessary, needed to be employed.
After conversion to kernfs, internal object lifetime and locking
rules are mostly isolated from vfs interactions allowing shedding
of several nasty hacks and overall simplification. This will also
allow implmentation of operations which may affect multiple cgroups
which weren't possible before as it would have required nesting
i_mutexes.
- Various simplifications including dropping of module support,
easier cgroup name/path handling, simplified cgroup file type
handling and task_cg_lists optimization.
- Prepatory changes for the planned unified hierarchy, which is still
a patchset away from being actually operational. The dummy
hierarchy is updated to serve as the default unified hierarchy.
Controllers which aren't claimed by other hierarchies are
associated with it, which BTW was what the dummy hierarchy was for
anyway.
- Various fixes from Li and others. This pull request includes some
patches to add missing slab.h to various subsystems. This was
triggered xattr.h include removal from cgroup.h. cgroup.h
indirectly got included a lot of files which brought in xattr.h
which brought in slab.h.
There are several merge commits - one to pull in kernfs updates
necessary for converting cgroup (already in upstream through
driver-core), others for interfering changes in the fixes branch"
* 'for-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (74 commits)
cgroup: remove useless argument from cgroup_exit()
cgroup: fix spurious lockdep warning in cgroup_exit()
cgroup: Use RCU_INIT_POINTER(x, NULL) in cgroup.c
cgroup: break kernfs active_ref protection in cgroup directory operations
cgroup: fix cgroup_taskset walking order
cgroup: implement CFTYPE_ONLY_ON_DFL
cgroup: make cgrp_dfl_root mountable
cgroup: drop const from @buffer of cftype->write_string()
cgroup: rename cgroup_dummy_root and related names
cgroup: move ->subsys_mask from cgroupfs_root to cgroup
cgroup: treat cgroup_dummy_root as an equivalent hierarchy during rebinding
cgroup: remove NULL checks from [pr_cont_]cgroup_{name|path}()
cgroup: use cgroup_setup_root() to initialize cgroup_dummy_root
cgroup: reorganize cgroup bootstrapping
cgroup: relocate setting of CGRP_DEAD
cpuset: use rcu_read_lock() to protect task_cs()
cgroup_freezer: document freezer_fork() subtleties
cgroup: update cgroup_transfer_tasks() to either succeed or fail
cgroup: drop task_lock() protection around task->cgroups
cgroup: update how a newly forked task gets associated with css_set
...
Replace the bh safe variant with the hard irq safe variant.
We need a hard irq safe variant to deal with netpoll transmitting
packets from hard irq context, and we need it in most if not all of
the places using the bh safe variant.
Except on 32bit uni-processor the code is exactly the same so don't
bother with a bh variant, just have a hard irq safe variant that
everyone can use.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
cgroup->name handling became quite complicated over time involving
dedicated struct cgroup_name for RCU protection. Now that cgroup is
on kernfs, we can drop all of it and simply use kernfs_name/path() and
friends. Replace cgroup->name and all related code with kernfs
name/path constructs.
* Reimplement cgroup_name() and cgroup_path() as thin wrappers on top
of kernfs counterparts, which involves semantic changes.
pr_cont_cgroup_name() and pr_cont_cgroup_path() added.
* cgroup->name handling dropped from cgroup_rename().
* All users of cgroup_name/path() updated to the new semantics. Users
which were formatting the string just to printk them are converted
to use pr_cont_cgroup_name/path() instead, which simplifies things
quite a bit. As cgroup_name() no longer requires RCU read lock
around it, RCU lockings which were protecting only cgroup_name() are
removed.
v2: Comment above oom_info_lock updated as suggested by Michal.
v3: dummy_top doesn't have a kn associated and
pr_cont_cgroup_name/path() ended up calling the matching kernfs
functions with NULL kn leading to oops. Test for NULL kn and
print "/" if so. This issue was reported by Fengguang Wu.
v4: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
cgroup_subsys is a bit messier than it needs to be.
* The name of a subsys can be different from its internal identifier
defined in cgroup_subsys.h. Most subsystems use the matching name
but three - cpu, memory and perf_event - use different ones.
* cgroup_subsys_id enums are postfixed with _subsys_id and each
cgroup_subsys is postfixed with _subsys. cgroup.h is widely
included throughout various subsystems, it doesn't and shouldn't
have claim on such generic names which don't have any qualifier
indicating that they belong to cgroup.
* cgroup_subsys->subsys_id should always equal the matching
cgroup_subsys_id enum; however, we require each controller to
initialize it and then BUG if they don't match, which is a bit
silly.
This patch cleans up cgroup_subsys names and initialization by doing
the followings.
* cgroup_subsys_id enums are now postfixed with _cgrp_id, and each
cgroup_subsys with _cgrp_subsys.
* With the above, renaming subsys identifiers to match the userland
visible names doesn't cause any naming conflicts. All non-matching
identifiers are renamed to match the official names.
cpu_cgroup -> cpu
mem_cgroup -> memory
perf -> perf_event
* controllers no longer need to initialize ->subsys_id and ->name.
They're generated in cgroup core and set automatically during boot.
* Redundant cgroup_subsys declarations removed.
* While updating BUG_ON()s in cgroup_init_early(), convert them to
WARN()s. BUGging that early during boot is stupid - the kernel
can't print anything, even through serial console and the trap
handler doesn't even link stack frame properly for back-tracing.
This patch doesn't introduce any behavior changes.
v2: Rebased on top of fe1217c4f3 ("net: net_cls: move cgroupfs
classid handling into core").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Ingo Molnar <mingo@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Thomas Graf <tgraf@suug.ch>
While u64_stats_fetch_retry is only preempt_disable on 32bit
UP system. This is not enough to avoid preemption by bh and
may read strange 64 bit value.
Signed-off-by: Hong Zhiguo <zhiguohong@tencent.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that seqcounts are lockdep enabled objects, we need to explicitly
initialize runtime allocated seqcounts so that lockdep can track them.
Without this patch, Fengguang was seeing:
[ 4.127282] INFO: trying to register non-static key.
[ 4.128027] the code is fine but needs lockdep annotation.
[ 4.128027] turning off the locking correctness validator.
[ 4.128027] CPU: 0 PID: 96 Comm: kworker/u4:1 Not tainted 3.12.0-next-20131108-10601-gbad570d #2
[ 4.128027] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ ... ]
[ 4.128027] Call Trace:
[ 4.128027] [<7908e744>] ? console_unlock+0x353/0x380
[ 4.128027] [<79dc7cf2>] dump_stack+0x48/0x60
[ 4.128027] [<7908953e>] __lock_acquire.isra.26+0x7e3/0xceb
[ 4.128027] [<7908a1c5>] lock_acquire+0x71/0x9a
[ 4.128027] [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
[ 4.128027] [<7940658b>] throtl_update_dispatch_stats+0x7c/0x153
[ 4.128027] [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
[ 4.128027] [<794079aa>] blk_throtl_bio+0x1c3/0x485
...
Use u64_stats_init() for all affected data structures, which initializes
the seqcount.
Reported-and-Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
[ Folded in another fix from the mailing list as well as a fix to that fix. Tweaked commit message. ]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1384314134-6895-1-git-send-email-john.stultz@linaro.org
[ So I actually think that the two SOBs from PeterZ are the right depiction of the patch route. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Previously, all css descendant iterators didn't include the origin
(root of subtree) css in the iteration. The reasons were maintaining
consistency with css_for_each_child() and that at the time of
introduction more use cases needed skipping the origin anyway;
however, given that css_is_descendant() considers self to be a
descendant, omitting the origin css has become more confusing and
looking at the accumulated use cases rather clearly indicates that
including origin would result in simpler code overall.
While this is a change which can easily lead to subtle bugs, cgroup
API including the iterators has recently gone through major
restructuring and no out-of-tree changes will be applicable without
adjustments making this a relatively acceptable opportunity for this
type of change.
The conversions are mostly straight-forward. If the iteration block
had explicit origin handling before or after, it's moved inside the
iteration. If not, if (pos == origin) continue; is added. Some
conversions add extra reference get/put around origin handling by
consolidating origin handling and the rest. While the extra ref
operations aren't strictly necessary, this shouldn't cause any
noticeable difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
cgroup is currently in the process of transitioning to using css
(cgroup_subsys_state) as the primary handle instead of cgroup in
subsystem API. For hierarchy iterators, this is beneficial because
* In most cases, css is the only thing subsystems care about anyway.
* On the planned unified hierarchy, iterations for different
subsystems will need to skip over different subtrees of the
hierarchy depending on which subsystems are enabled on each cgroup.
Passing around css makes it unnecessary to explicitly specify the
subsystem in question as css is intersection between cgroup and
subsystem
* For the planned unified hierarchy, css's would need to be created
and destroyed dynamically independent from cgroup hierarchy. Having
cgroup core manage css iteration makes enforcing deref rules a lot
easier.
Most subsystem conversions are straight-forward. Noteworthy changes
are
* blkio: cgroup_to_blkcg() is no longer used. Removed.
* freezer: cgroup_freezer() is no longer used. Removed.
* devices: cgroup_to_devcgroup() is no longer used. Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Currently, controllers have to explicitly follow the cgroup hierarchy
to find the parent of a given css. cgroup is moving towards using
cgroup_subsys_state as the main controller interface construct, so
let's provide a way to climb the hierarchy using just csses.
This patch implements css_parent() which, given a css, returns its
parent. The function is guarnateed to valid non-NULL parent css as
long as the target css is not at the top of the hierarchy.
freezer, cpuset, cpu, cpuacct, hugetlb, memory, net_cls and devices
are converted to use css_parent() instead of accessing cgroup->parent
directly.
* __parent_ca() is dropped from cpuacct and its usage is replaced with
parent_ca(). The only difference between the two was NULL test on
cgroup->parent which is now embedded in css_parent() making the
distinction moot. Note that eventually a css->parent field will be
added to css and the NULL check in css_parent() will go away.
This patch shouldn't cause any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
css (cgroup_subsys_state) is usually embedded in a subsys specific
data structure. Subsystems either use container_of() directly to cast
from css to such data structure or has an accessor function wrapping
such cast. As cgroup as whole is moving towards using css as the main
interface handle, add and update such accessors to ease dealing with
css's.
All accessors explicitly handle NULL input and return NULL in those
cases. While this looks like an extra branch in the code, as all
controllers specific data structures have css as the first field, the
casting doesn't involve any offsetting and the compiler can trivially
optimize out the branch.
* blkio, freezer, cpuset, cpu, cpuacct and net_cls didn't have such
accessor. Added.
* memory, hugetlb and devices already had one but didn't explicitly
handle NULL input. Updated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
The names of the two struct cgroup_subsys_state accessors -
cgroup_subsys_state() and task_subsys_state() - are somewhat awkward.
The former clashes with the type name and the latter doesn't even
indicate it's somehow related to cgroup.
We're about to revamp large portion of cgroup API, so, let's rename
them so that they're less awkward. Most per-controller usages of the
accessors are localized in accessor wrappers and given the amount of
scheduled changes, this isn't gonna add any noticeable headache.
Rename cgroup_subsys_state() to cgroup_css() and task_subsys_state()
to task_css(). This patch is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, when the last reference of a blkcg_gq is put, all then
release operations sans the actual freeing happen directly in
blkg_put(). As blkg_put() may be called under queue_lock, all
pd_exit_fn()s may be too. This makes it impossible for pd_exit_fn()s
to use del_timer_sync() on timers which grab the queue_lock which is
an irq-safe lock due to the deadlock possibility described in the
comment on top of del_timer_sync().
This can be easily avoided by perfoming the release operations in the
RCU callback instead of directly from blkg_put(). This patch moves
the blkcg_gq release operations to the RCU callback.
As this leaves __blkg_release() with only call_rcu() invocation,
blkg_rcu_free() is renamed to __blkg_release_rcu(), exported and
call_rcu() invocation is now done directly from blkg_put() instead of
going through __blkg_release() which is removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
blk-throttle hierarchy support will make use of it. Move
blkg_for_each_descendant_pre() from block/blk-cgroup.c to
block/blk-cgroup.h.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
rename() will change dentry->d_name. The result of this race can
be worse than seeing partially rewritten name, but we might access
a stale pointer because rename() will re-allocate memory to hold
a longer name.
As accessing dentry->name must be protected by dentry->d_lock or
parent inode's i_mutex, while on the other hand cgroup-path() can
be called with some irq-safe spinlocks held, we can't generate
cgroup path using dentry->d_name.
Alternatively we make a copy of dentry->d_name and save it in
cgrp->name when a cgroup is created, and update cgrp->name at
rename().
v5: use flexible array instead of zero-size array.
v4: - allocate root_cgroup_name and all root_cgroup->name points to it.
- add cgroup_name() wrapper.
v3: use kfree_rcu() instead of synchronize_rcu() in user-visible path.
v2: make cgrp->name RCU safe.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Implement blkg_[rw]stat_recursive_sum() and blkg_[rw]stat_merge().
The former two collect the [rw]stats designated by the target policy
data and offset from the pd's subtree. The latter two add one
[rw]stat to another.
Note that the recursive sum functions require the queue lock to be
held on entry to make blkg online test reliable. This is necessary to
properly handle stats of a dying blkg.
These will be used to implement hierarchical stats.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Rename blkg_rwstat_sum() to blkg_rwstat_total(). sum will be used for
summing up stats from multiple blkgs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Add two blkcg_policy methods, ->online_pd_fn() and ->offline_pd_fn(),
which are invoked as the policy_data gets activated and deactivated
while holding both blkcg and q locks.
Also, add blkcg_gq->online bool, which is set and cleared as the
blkcg_gq gets activated and deactivated. This flag also is toggled
while holding both blkcg and q locks.
These will be used to implement hierarchical stats.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Add pd->plid so that the policy a pd belongs to can be identified
easily. This will be used to implement hierarchical blkg_[rw]stats.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
cfq blkcg is about to grow proper hierarchy handling, where a child
blkg's weight would nest inside the parent's. This makes tasks in a
blkg to compete against both tasks in the sibling blkgs and the tasks
of child blkgs.
We're gonna use the existing weight as the group weight which decides
the blkg's weight against its siblings. This patch introduces a new
weight - leaf_weight - which decides the weight of a blkg against the
child blkgs.
It's named leaf_weight because another way to look at it is that each
internal blkg nodes have a hidden child leaf node which contains all
its tasks and leaf_weight is the weight of the leaf node and handled
the same as the weight of the child blkgs.
This patch only adds leaf_weight fields and exposes it to userland.
The new weight isn't actually used anywhere yet. Note that
cfq-iosched currently offcially supports only single level hierarchy
and root blkgs compete with the first level blkgs - ie. root weight is
basically being used as leaf_weight. For root blkgs, the two weights
are kept in sync for backward compatibility.
v2: cfqd->root_group->leaf_weight initialization was missing from
cfq_init_queue() causing divide by zero when
!CONFIG_CFQ_GROUP_SCHED. Fix it. Reported by Fengguang.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Currently a child blkg (blkcg_gq) can be created even if its parent
doesn't exist. ie. Given a blkg, it's not guaranteed that its
ancestors will exist. This makes it difficult to implement proper
hierarchy support for blkcg policies.
Always create blkgs recursively and make a child blkg hold a reference
to its parent. blkg->parent is added so that finding the parent is
easy. blkcg_parent() is also added in the process.
This change can be visible to userland. e.g. while issuing IO in a
nested cgroup didn't affect the ancestors at all, now it will
initialize all ancestor blkgs and zero stats for the request_queue
will always appear on them. While this is userland visible, this
shouldn't cause any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Currently, request_queue has one request_list to allocate requests
from regardless of blkcg of the IO being issued. When the unified
request pool is used up, cfq proportional IO limits become meaningless
- whoever grabs the next request being freed wins the race regardless
of the configured weights.
This can be easily demonstrated by creating a blkio cgroup w/ very low
weight, put a program which can issue a lot of random direct IOs there
and running a sequential IO from a different cgroup. As soon as the
request pool is used up, the sequential IO bandwidth crashes.
This patch implements per-blkg request_list. Each blkg has its own
request_list and any IO allocates its request from the matching blkg
making blkcgs completely isolated in terms of request allocation.
* Root blkcg uses the request_list embedded in each request_queue,
which was renamed to @q->root_rl from @q->rq. While making blkcg rl
handling a bit harier, this enables avoiding most overhead for root
blkcg.
* Queue fullness is properly per request_list but bdi isn't blkcg
aware yet, so congestion state currently just follows the root
blkcg. As writeback isn't aware of blkcg yet, this works okay for
async congestion but readahead may get the wrong signals. It's
better than blkcg completely collapsing with shared request_list but
needs to be improved with future changes.
* After this change, each block cgroup gets a full request pool making
resource consumption of each cgroup higher. This makes allowing
non-root users to create cgroups less desirable; however, note that
allowing non-root users to directly manage cgroups is already
severely broken regardless of this patch - each block cgroup
consumes kernel memory and skews IO weight (IO weights are not
hierarchical).
v2: queue-sysfs.txt updated and patch description udpated as suggested
by Vivek.
v3: blk_get_rl() wasn't checking error return from
blkg_lookup_create() and may cause oops on lookup failure. Fix it
by falling back to root_rl on blkg lookup failures. This problem
was spotted by Rakesh Iyer <rni@google.com>.
v4: Updated to accomodate 458f27a982 "block: Avoid missed wakeup in
request waitqueue". blk_drain_queue() now wakes up waiters on all
blkg->rl on the target queue.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Make bio_blkcg() and friends inline. They all are very simple and
used only in few places.
This patch is to prepare for further updates to request allocation
path.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkg lookup is currently performed by traversing linked list anchored
at blkcg->blkg_list. This is very unscalable and with blk-throttle
enabled and enough request queues on the system, this can get very
ugly quickly (blk-throttle performs look up on every bio submission).
This patch makes blkcg use radix tree to index blkgs combined with
simple last-looked-up hint. This is mostly identical to how icqs are
indexed from ioc.
Note that because __blkg_lookup() may be invoked without holding queue
lock, hint is only updated from __blkg_lookup_create(). Due to cfq's
cfqq caching, this makes hint updates overly lazy. This will be
improved with scheduled blkcg aware request allocation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There's no reason to keep blkcg_policy_ops separate. Collapse it into
blkcg_policy.
This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently blkg_policy_data carries policy specific data as char flex
array instead of being embedded in policy specific data. This was
forced by oddities around blkg allocation which are all gone now.
This patch makes blkg_policy_data embedded in policy specific data -
throtl_grp and cfq_group so that it's more conventional and consistent
with how io_cq is handled.
* blkcg_policy->pdata_size is renamed to ->pd_size.
* Functions which used to take void *pdata now takes struct
blkg_policy_data *pd.
* blkg_to_pdata/pdata_to_blkg() updated to blkg_to_pd/pd_to_blkg().
* Dummy struct blkg_policy_data definition added. Dummy
pdata_to_blkg() definition was unused and inconsistent with the
non-dummy version - correct dummy pd_to_blkg() added.
* throtl and cfq updated accordingly.
* As dummy blkg_to_pd/pd_to_blkg() are provided,
blkg_to_cfqg/cfqg_to_blkg() don't need to be ifdef'd. Moved outside
ifdef block.
This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
During the recent blkcg cleanup, most of blkcg API has changed to such
extent that mass renaming wouldn't cause any noticeable pain. Take
the chance and cleanup the naming.
* Rename blkio_cgroup to blkcg.
* Drop blkio / blkiocg prefixes and consistently use blkcg.
* Rename blkio_group to blkcg_gq, which is consistent with io_cq but
keep the blkg prefix / variable name.
* Rename policy method type and field names to signify they're dealing
with policy data.
* Rename blkio_policy_type to blkcg_policy.
This patch doesn't cause any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
* Update indentation on struct field declarations.
* Uniformly don't use "extern" on function declarations.
* Merge the two #ifdef CONFIG_BLK_CGROUP blocks.
All changes in this patch are cosmetic.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkio_group->path[] stores the path of the associated cgroup and is
used only for debug messages. Just format the path from blkg->cgroup
when printing debug messages.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
* All_q_list is unused. Drop all_q_{mutex|list}.
* @for_root of blkg_lookup_create() is always %false when called from
outside blk-cgroup.c proper. Factor out __blkg_lookup_create() so
that it doesn't check whether @q is bypassing and use the
underscored version for the @for_root callsite.
* blkg_destroy_all() is used only from blkcg proper and @destroy_root
is always %true. Make it static and drop @destroy_root.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
All blkcg policies were assumed to be enabled on all request_queues.
Due to various implementation obstacles, during the recent blkcg core
updates, this was temporarily implemented as shooting down all !root
blkgs on elevator switch and policy [de]registration combined with
half-broken in-place root blkg updates. In addition to being buggy
and racy, this meant losing all blkcg configurations across those
events.
Now that blkcg is cleaned up enough, this patch replaces the temporary
implementation with proper per-queue policy activation. Each blkcg
policy should call the new blkcg_[de]activate_policy() to enable and
disable the policy on a specific queue. blkcg_activate_policy()
allocates and installs policy data for the policy for all existing
blkgs. blkcg_deactivate_policy() does the reverse. If a policy is
not enabled for a given queue, blkg printing / config functions skip
the respective blkg for the queue.
blkcg_activate_policy() also takes care of root blkg creation, and
cfq_init_queue() and blk_throtl_init() are updated accordingly.
This replaces blkcg_bypass_{start|end}() and update_root_blkg_pd()
unnecessary. Dropped.
v2: cfq_init_queue() was returning uninitialized @ret on root_group
alloc failure if !CONFIG_CFQ_GROUP_IOSCHED. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add @pol to blkg_conf_prep() and let it return with queue lock held
(to be released by blkg_conf_finish()). Note that @pol isn't used
yet.
This is to prepare for per-queue policy activation and doesn't cause
any visible difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Remove BLKIO_POLICY_* enums and let blkio_policy_register() allocate
@pol->plid dynamically on registration. The maximum number of blkcg
policies which can be registered at the same time is defined by
BLKCG_MAX_POLS constant added to include/linux/blkdev.h.
Note that blkio_policy_register() now may fail. Policy init functions
updated accordingly and unnecessary ifdefs removed from cfq_init().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The two functions were taking "enum blkio_policy_id plid". Make them
take "const struct blkio_policy_type *pol" instead.
This is to prepare for per-queue policy activation and doesn't cause
any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With blkio_policy[], blkio_list is redundant and hinders with
per-queue policy activation. Remove it. Also, replace
blkio_list_lock with a mutex blkcg_pol_mutex and let it protect the
whole [un]registration.
This is to prepare for per-queue policy activation and doesn't cause
any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that all stat handling code lives in policy implementations,
there's no need to encode policy ID in cft->private.
* Export blkcg_prfill_[rw]stat() from blkcg, remove
blkcg_print_[rw]stat(), and implement cfqg_print_[rw]stat() which
use hard-code BLKIO_POLICY_PROP.
* Use cft->private for offset of the target field directly and drop
BLKCG_STAT_{PRIV|POL|OFF}().
Signed-off-by: Tejun Heo <tj@kernel.org>
Now that all conf and stat fields are moved into policy specific
blkio_policy_data->pdata areas, there's no reason to use
blkio_policy_data itself in prfill functions. Pass around @pd->pdata
instead of @pd.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkio_cgroup_conf->iops and ->bps are owned by blk-throttle and has no
reason to be defined in blkcg core. Drop them and let conf setting
functions directly manipulate throtl_grp->bps[] and ->iops[].
This makes blkio_group_conf empty. Drop it.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkio_group_conf->weight is owned by cfq and has no reason to be
defined in blkcg core. Replace it with cfq_group->dev_weight and let
conf setting functions directly set it. If dev_weight is zero, the
cfqg doesn't have device specific weight configured.
Also, rename BLKIO_WEIGHT_* constants to CFQ_WEIGHT_* and rename
blkio_cgroup->weight to blkio_cgroup->cfq_weight. We eventually want
per-policy storage in blkio_cgroup but just mark the ownership of the
field for now.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkio_group_stats_cpu is used only by blk-throtl and has no reason to
be defined in blkcg core.
* Move blkio_group_stats_cpu to blk-throttle.c and rename it to
tg_stats_cpu.
* blkg_policy_data->stats_cpu is replaced with throtl_grp->stats_cpu.
prfill functions updated accordingly.
* All related macros / functions are renamed so that they have tg_
prefix and the unnecessary @pol arguments are dropped.
* Per-cpu stats allocation code is also moved from blk-cgroup.c to
blk-throttle.c and gets simplified to only deal with
BLKIO_POLICY_THROTL. percpu stat free is performed by the exit
method throtl_exit_blkio_group().
* throtl_reset_group_stats() implemented for
blkio_reset_group_stats_fn method so that tg->stats_cpu can be
reset.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkio_group_stats contains only fields used by cfq and has no reason
to be defined in blkcg core.
* Move blkio_group_stats to cfq-iosched.c and rename it to cfqg_stats.
* blkg_policy_data->stats is replaced with cfq_group->stats.
blkg_prfill_[rw]stat() are updated to use offset against pd->pdata
instead.
* All related macros / functions are renamed so that they have cfqg_
prefix and the unnecessary @pol arguments are dropped.
* All stat functions now take cfq_group * instead of blkio_group *.
* lockdep assertion on queue lock dropped. Elevator runs under queue
lock by default. There isn't much to be gained by adding lockdep
assertions at stat function level.
* cfqg_stats_reset() implemented for blkio_reset_group_stats_fn method
so that cfqg->stats can be reset.
Signed-off-by: Tejun Heo <tj@kernel.org>
Add blkio_policy_ops->blkio_exit_group_fn() and
->blkio_reset_group_stats_fn(). These will be used to further
modularize blkcg policy implementation.
Signed-off-by: Tejun Heo <tj@kernel.org>
blkio_group_stats_cpu is used to count dispatch stats using per-cpu
counters. This is used by both blk-throtl and cfq-iosched but the
sharing is rather silly.
* cfq-iosched doesn't need per-cpu dispatch stats. cfq always updates
those stats while holding queue_lock.
* blk-throtl needs per-cpu dispatch stats but only service_bytes and
serviced. It doesn't make use of sectors.
This patch makes cfq add and use global stats for service_bytes,
serviced and sectors, removes per-cpu sectors counter and moves
per-cpu stat printing code to blk-throttle.c.
Signed-off-by: Tejun Heo <tj@kernel.org>
