| Commit message (Collapse) | Author | Age | Files | Lines |
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* 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>
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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>
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With per-queue policy activation, root blkg creation will be moved to
blkcg core. Add q->root_blkg in preparation. For blk-throtl, this
replaces throtl_data->root_tg; however, cfq needs to keep
cfqd->root_group for !CONFIG_CFQ_GROUP_IOSCHED.
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>
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With the previous change to guarantee bypass visiblity for RCU read
lock regions, entering bypass mode involves non-trivial overhead and
future changes are scheduled to make use of bypass mode during init
path. Combined it may end up adding noticeable delay during boot.
This patch makes request_queue start its life in bypass mode, which is
ended on queue init completion at the end of
blk_init_allocated_queue(), and updates blk_queue_bypass_start() such
that draining and RCU synchronization are performed only when the
queue actually enters bypass mode.
This avoids unnecessarily switching in and out of bypass mode during
init avoiding the overhead and any nasty surprises which may step from
leaving bypass mode on half-initialized queues.
The boot time overhead was pointed out by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Currently, blkg_lookup() doesn't check @q bypass state. This patch
updates blk_queue_bypass_start() to do synchronize_rcu() before
returning and updates blkg_lookup() to check blk_queue_bypass() and
return %NULL if bypassing. This ensures blkg_lookup() returns %NULL
if @q is bypassing.
This is to guarantee that nobody is accessing policy data while @q is
bypassing, which is necessary to allow replacing blkio_cgroup->pd[] in
place on policy [de]activation.
v2: Added more comments explaining bypass guarantees as suggested by
Vivek.
v3: Added more comments explaining why there's no synchronize_rcu() in
blk_cleanup_queue() as suggested by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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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>
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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>
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blkcg_print_blkgs()
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>
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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>
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* CFQ_WEIGHT_* defined inside CONFIG_BLK_CGROUP causes cfq-iosched.c
compile failure when the config is disabled. Move it outside the
ifdef block.
* Dummy cfqg_stats_*() definitions were lacking inline modifiers
causing unused functions warning if !CONFIG_CFQ_GROUP_IOSCHED. Add
them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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As with conf/stats file handling code, there's no reason for stat
update code to live in blkcg core with policies calling into update
them. The current organization is both inflexible and complex.
This patch moves stat update code to specific policies. All
blkiocg_update_*_stats() functions which deal with BLKIO_POLICY_PROP
stats are collapsed into their cfq_blkiocg_update_*_stats()
counterparts. blkiocg_update_dispatch_stats() is used by both
policies and duplicated as throtl_update_dispatch_stats() and
cfq_blkiocg_update_dispatch_stats(). This will be cleaned up later.
Signed-off-by: Tejun Heo <tj@kernel.org>
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block/cfq.h contains some functions which interact with blkcg;
however, this is only part of it and cfq-iosched.c already has quite
some #ifdef CONFIG_CFQ_GROUP_IOSCHED. With conf/stat handling being
moved to specific policies, having these relay functions isolated in
cfq.h doesn't make much sense. Collapse cfq.h into cfq-iosched.c for
now. Let's split blkcg support properly later if necessary.
Signed-off-by: Tejun Heo <tj@kernel.org>
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blkcg conf/stat handling is convoluted in that details which belong to
specific policy implementations are all out in blkcg core and then
policies hook into core layer to access and manipulate confs and
stats. This sadly achieves both inflexibility (confs/stats can't be
modified without messing with blkcg core) and complexity (all the
call-ins and call-backs).
The previous patches restructured conf and stat handling code such
that they can be separated out. This patch relocates the file
handling part. All conf/stat file handling code which belongs to
BLKIO_POLICY_PROP is moved to cfq-iosched.c and all
BKLIO_POLICY_THROTL code to blk-throtl.c.
The move is verbatim except for blkio_update_group_{weight|bps|iops}()
callbacks which relays conf changes to policies. The configuration
settings are handled in policies themselves so the relaying isn't
necessary. Conf setting functions are modified to directly call
per-policy update functions and the relaying mechanism is dropped.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Add blkiop->cftypes which is added and removed together with the
policy. This will be used to move conf/stat handling to the policies.
Signed-off-by: Tejun Heo <tj@kernel.org>
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conf/stat handling is about to be moved to policy implementation from
blkcg core. Export conf/stat helpers from blkcg core so that
blk-throttle and cfq-iosched can use them.
Signed-off-by: Tejun Heo <tj@kernel.org>
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blkg_conf_prep() implements "MAJ:MIN VAL" parsing manually, which is
unnecessary. Just use sscanf("%u:%u %llu"). This might not reject
some malformed input (extra input at the end) but we don't care.
Signed-off-by: Tejun Heo <tj@kernel.org>
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As part of userland interface restructuring, this patch updates
per-blkio_group configuration setting. Instead of funneling
everything through a master function which has hard-coded cases for
each config file it may handle, the common part is factored into
blkg_conf_prep() and blkg_conf_finish() and different configuration
setters are implemented using the helpers.
While this doesn't result in immediate LOC reduction, this enables
further cleanups and more modular implementation.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Similarly to the previous stat restructuring, this patch restructures
conf printing code such that,
* Conf printing uses the same helpers as stat.
* Printing function doesn't require hardcoded switching on the config
being printed. Note that this isn't complete yet for throttle
confs. The next patch will convert setting for these confs and will
complete the transition.
* Printing uses read_seq_string callback (other methods will be phased
out).
Note that blkio_group_conf.iops[2] is changed to u64 so that they can
be manipulated with the same functions. This is transitional and will
go away later.
After this patch, per-device configurations - weight, bps and iops -
use __blkg_prfill_u64() for printing which uses white space as
delimiter instead of tab.
Signed-off-by: Tejun Heo <tj@kernel.org>
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blkiocg_file_write_u64() has single switch case. Drop
blkiocg_file_write_u64(), rename blkio_weight_write() to
blkcg_set_weight() and use it directly for .write_u64 callback.
Signed-off-by: Tejun Heo <tj@kernel.org>
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blkcg stats handling is a mess. None of the stats has much to do with
blkcg core but they are all implemented in blkcg core. Code sharing
is achieved by mixing common code with hard-coded cases for each stat
counter.
This patch restructures statistics printing such that
* Common logic exists as helper functions and specific print functions
use the helpers to implement specific cases.
* Printing functions serving multiple counters don't require hardcoded
switching on specific counters.
* Printing uses read_seq_string callback (other methods will be phased
out).
This change enables further cleanups and relocating stats code to the
policy implementation it belongs to.
Signed-off-by: Tejun Heo <tj@kernel.org>
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blkcg uses u64_stats_sync to avoid reading wrong u64 statistic values
on 32bit archs and some stat counters have subtypes to distinguish
read/writes and sync/async IOs. The stat code paths are confusing and
involve a lot of going back and forth between blkcg core and specific
policy implementations, and synchronization and subtype handling are
open coded in blkcg core.
This patch introduces struct blkg_stat and blkg_rwstat which, with
accompanying operations, encapsulate stat updating and accessing with
proper synchronization.
blkg_stat is simple u64 counter with 64bit read-access protection.
blkg_rwstat is the one with rw and [a]sync subcounters and takes @rw
flags to distinguish IO subtypes (%REQ_WRITE and %REQ_SYNC) and
replaces stat_sub_type indexed arrays.
All counters in blkio_group_stats and blkio_group_stats_cpu are
replaced with either blkg_stat or blkg_rwstat along with all users.
This does add one u64_stats_sync per counter and increase stats_sync
operations but they're empty/noops on 64bit archs and blkcg doesn't
have too many counters, especially with DEBUG_BLK_CGROUP off.
While the currently resulting code isn't necessarily simpler at the
moment, this will enable further clean up of blkcg stats code.
- BLKIO_STAT_{READ|WRITE|SYNC|ASYNC|TOTAL} renamed to
BLKG_RWSTAT_{READ|WRITE|SYNC|ASYNC|TOTAL}.
- blkg_stat_add() replaces blkio_add_stat() and
blkio_check_and_dec_stat(). Note that BUG_ON() on underflow in the
latter function no longer exists. It's *way* better to have
underflowed stat counters than oopsing.
- blkio_group_stats->dequeue is now a proper u64 stat counter instead
of ulong.
- reset_stats() updated to clear each stat counters individually and
BLKG_STATS_DEBUG_CLEAR_{START|SIZE} are removed.
- Some functions reconstruct rw flags from direction and sync
booleans. This will be removed by future patches.
Signed-off-by: Tejun Heo <tj@kernel.org>
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BLKIO_STAT_CPU_SECTORS doesn't need read/write/sync/async subcounters
and is counted by blkio_group_stats_cpu->sectors; however, it still
holds a member in blkio_group_stats_cpu->stat_arr_cpu.
Rearrange stat_type_cpu and define BLKIO_STAT_CPU_ARR_NR and use it
for stat_arr_cpu[] size so that only SERVICE_BYTES and SERVICED have
subcounters.
Signed-off-by: Tejun Heo <tj@kernel.org>
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@pol to blkg_to_pdata() and @plid to blkg_lookup_create() are no
longer necessary. Drop them.
Signed-off-by: Tejun Heo <tj@kernel.org>
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cgroup/for-3.5 contains the following changes which blk-cgroup needs
to proceed with the on-going cleanup.
* Dynamic addition and removal of cftypes to make config/stat file
handling modular for policies.
* cgroup removal update to not wait for css references to drain to fix
blkcg removal hang caused by cfq caching cfqgs.
Pull in cgroup/for-3.5 into block/for-3.5/core. This causes the
following conflicts in block/blk-cgroup.c.
* 761b3ef50e "cgroup: remove cgroup_subsys argument from callbacks"
conflicts with blkiocg_pre_destroy() addition and blkiocg_attach()
removal. Resolved by removing @subsys from all subsys methods.
* 676f7c8f84 "cgroup: relocate cftype and cgroup_subsys definitions in
controllers" conflicts with ->pre_destroy() and ->attach() updates
and removal of modular config. Resolved by dropping forward
declarations of the methods and applying updates to the relocated
blkio_subsys.
* 4baf6e3325 "cgroup: convert all non-memcg controllers to the new
cftype interface" builds upon the previous item. Resolved by adding
->base_cftypes to the relocated blkio_subsys.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Smatch complains that we re-enable IRQs twice. It looks like we forgot
to disable them here on the spin_trylock() failure path. This was added
in 9f13ef678e "blkcg: use double locking instead of RCU for blkg
synchronization".
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>`
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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When BLK_CGROUP is enabled but CFQ_GROUP_IOSCHED is, cfq ends up
calling blkg_get/put() on dummy cfqg leading to the following crash.
BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0
IP: [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430
PGD 0
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
CPU 0
Modules linked in:
Pid: 1, comm: swapper/0 Not tainted 3.3.0-rc6-work+ #125 Bochs Bochs
RIP: 0010:[<ffffffff813d44d8>] [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430
RSP: 0018:ffff88001f9dfd80 EFLAGS: 00010046
RAX: ffff88001aefbbf0 RBX: ffff88001aeedbf0 RCX: 0000000000000100
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff820ffd40
RBP: ffff88001f9dfdd0 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000009 R14: ffff88001aefbc30 R15: 0000000000000003
FS: 0000000000000000(0000) GS:ffff88001fc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00000000000000b0 CR3: 000000000206f000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process swapper/0 (pid: 1, threadinfo ffff88001f9de000, task ffff88001f9dc040)
Stack:
ffff88001aeedbf0 ffff88001aefbdb0 ffff88001aef1548 ffff88001aefbbf0
ffff88001f9dfdd0 ffff88001aef1548 ffffffff820d6320 ffffffff8165ce30
ffffffff82c555e0 ffff88001aeebbf0 ffff88001f9dfe00 ffffffff813b0507
Call Trace:
[<ffffffff813b0507>] elevator_init+0xd7/0x140
[<ffffffff813b83d5>] blk_init_allocated_queue+0x125/0x150
[<ffffffff813b94d3>] blk_init_queue_node+0x43/0x80
[<ffffffff813b9523>] blk_init_queue+0x13/0x20
[<ffffffff821aec00>] floppy_init+0x82/0xec7
[<ffffffff810001d2>] do_one_initcall+0x42/0x170
[<ffffffff821835fc>] kernel_init+0xcb/0x14f
[<ffffffff81b40b24>] kernel_thread_helper+0x4/0x10
Code: 00 e8 1d 9e 76 00 48 8b 43 48 48 85 c0 48 89 83 28 03 00 00 74 07 4c 8b a0 10 ff ff ff 8b 15 b0 2e d0 00 85 d2 0f 85 49 01 00 00 <41> 8b 84 24 b0 00 00 00 85 c0 0f 8e 8c 01 00 00 83 e8 01 85 c0
RIP [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430
Because cfq's blkcg support has a on/off switch, CFQ_GROUP_IOSCHED,
separate from BLK_CGROUP, blkg access through cfqg needs to be
conditioned on it.
* Make blkg_to_cfqg() and cfqg_to_blkg() conditioned on
CFQ_GROUP_IOSCHED. If disabled, they always return %NULL.
* Introduce cfqg_get() and cfqg_put() conditioned on
CFQ_GROUP_IOSCHED. If disabled, they are noops.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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After the previous patch to cfq, there's no ioc_get_changed() user
left. This patch yanks out ioc_{ioprio|cgroup|get}_changed() and all
related stuff.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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cfq caches the associated cfqq's for a given cic. The cache needs to
be flushed if the cic's ioprio or blkcg has changed. It is currently
done by requiring the changing action to set the respective
ICQ_*_CHANGED bit in the icq and testing it from cfq_set_request(),
which involves iterating through all the affected icqs.
All cfq wants to know is whether ioprio and/or blkcg have changed
since the last flush and can be easily achieved by just remembering
the current ioprio and blkcg ID in cic.
This patch adds cic->{ioprio|blkcg_id}, updates all ioprio users to
use the remembered value instead, and updates cfq_set_request() path
such that, instead of using icq_get_changed(), the current values are
compared against the remembered ones and trigger appropriate flush
action if not. Condition tests are moved inside both _changed
functions which are now named check_ioprio_changed() and
check_blkcg_changed().
ioprio.h::task_ioprio*() can't be used anymore and replaced with
open-coded IOPRIO_CLASS_NONE case in cfq_async_queue_prio().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Now that io_cq is managed by block core and guaranteed to exist for
any in-flight request, it is easier and carries more information to
pass around cfq_io_cq than io_context.
This patch updates cfq_init_prio_data(), cfq_find_alloc_queue() and
cfq_get_queue() to take @cic instead of @ioc. This change removes a
duplicate cfq_cic_lookup() from cfq_find_alloc_queue().
This change enables the use of cic-cached ioprio in the next patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Add 64bit unique id to blkcg. This will be used by policies which
want blkcg identity test to tell whether the associated blkcg has
changed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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With recent plug merge updates, all non-percpu stat updates happen
under queue_lock making stats_lock unnecessary to synchronize stat
updates. The only synchronization necessary is stat reading, which
can be done using u64_stats_sync instead.
This patch removes blkio_group->stats_lock and adds
blkio_group_stats->syncp for reader synchronization.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Restructure blkio_get_stat() to prepare for removal of stats_lock.
* Define BLKIO_STAT_ARR_NR explicitly to denote which stats have
subtypes instead of using BLKIO_STAT_QUEUED.
* Separate out stat acquisition and printing. After this, there are
only two users of blkio_fill_stat(). Just open code it.
* The code was mixing MAX_KEY_LEN and MAX_KEY_LEN - 1. There's no
need to subtract one. Use MAX_KEY_LEN consistently.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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blkiocg_reset_stats() implements stat reset for blkio.reset_stats
cgroupfs file. This feature is very unconventional and something
which shouldn't have been merged. It's only useful when there's only
one user or tool looking at the stats. As soon as multiple users
and/or tools are involved, it becomes useless as resetting disrupts
other usages. There are very good reasons why all other stats expect
readers to read values at the start and end of a period and subtract
to determine delta over the period.
The implementation is rather complex - some fields shouldn't be
cleared and it saves some fields, resets whole and restores for some
reason. Reset of percpu stats is also racy. The comment points to
64bit store atomicity for the reason but even without that stores for
zero can simply race with other CPUs doing RMW and get clobbered.
Simplify reset by
* Clear selectively instead of resetting and restoring.
* Grouping debug stat fields to be reset and using memset() over them.
* Not caring about stats_lock.
* Using memset() to reset percpu stats.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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With recent plug merge updates, merged stats are no longer called for
plug merges and now only updated while holding queue_lock. As
stats_lock is scheduled to be removed, there's no reason to use percpu
for merged stats. Don't use percpu for merged stats.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Current per cpu stat allocation assumes GFP_KERNEL allocation flag. But in
IO path there are times when we want GFP_NOIO semantics. As there is no
way to pass the allocation flags to alloc_percpu(), this patch delays the
allocation of stats using a worker thread.
v2-> tejun suggested following changes. Changed the patch accordingly.
- move alloc_node location in structure
- reduce the size of names of some of the fields
- Reduce the scope of locking of alloc_list_lock
- Simplified stat_alloc_fn() by allocating stats for all
policies in one go and then assigning these to a group.
v3 -> Andrew suggested to put some comments in the code. Also raised
concerns about trying to allocate infinitely in case of allocation
failure. I have changed the logic to sleep for 10ms before retrying.
That should take care of non-preemptible UP kernels.
v4 -> Tejun had more suggestions.
- drop list_for_each_entry_all()
- instead of msleep() use queue_delayed_work()
- Some cleanups realted to more compact coding.
v5-> tejun suggested more cleanups leading to more compact code.
tj: - Relocated pcpu_stats into blkio_stat_alloc_fn().
- Minor comment update.
- This also fixes suspicious RCU usage warning caused by invoking
cgroup_path() from blkg_alloc() without holding RCU read lock.
Now that blkg_alloc() doesn't require sleepable context, RCU
read lock from blkg_lookup_create() is maintained throughout
blkg_alloc().
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Make blk-throttle call bio_associate_current() on bios being delayed
such that they get issued to block layer with the original io_context.
This allows stacking blk-throttle and cfq-iosched propio policies.
bios will always be issued with the correct ioc and blkcg whether it
gets delayed by blk-throttle or not.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Implement bio_blkio_cgroup() which returns the blkcg associated with
the bio if exists or %current's blkcg, and use it in blk-throttle and
cfq-iosched propio. This makes both cgroup policies honor task
association for the bio instead of always assuming %current.
As nobody is using bio_set_task() yet, this doesn't introduce any
behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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IO scheduling and cgroup are tied to the issuing task via io_context
and cgroup of %current. Unfortunately, there are cases where IOs need
to be routed via a different task which makes scheduling and cgroup
limit enforcement applied completely incorrectly.
For example, all bios delayed by blk-throttle end up being issued by a
delayed work item and get assigned the io_context of the worker task
which happens to serve the work item and dumped to the default block
cgroup. This is double confusing as bios which aren't delayed end up
in the correct cgroup and makes using blk-throttle and cfq propio
together impossible.
Any code which punts IO issuing to another task is affected which is
getting more and more common (e.g. btrfs). As both io_context and
cgroup are firmly tied to task including userland visible APIs to
manipulate them, it makes a lot of sense to match up tasks to bios.
This patch implements bio_associate_current() which associates the
specified bio with %current. The bio will record the associated ioc
and blkcg at that point and block layer will use the recorded ones
regardless of which task actually ends up issuing the bio. bio
release puts the associated ioc and blkcg.
It grabs and remembers ioc and blkcg instead of the task itself
because task may already be dead by the time the bio is issued making
ioc and blkcg inaccessible and those are all block layer cares about.
elevator_set_req_fn() is updated such that the bio elvdata is being
allocated for is available to the elevator.
This doesn't update block cgroup policies yet. Further patches will
implement the support.
-v2: #ifdef CONFIG_BLK_CGROUP added around bio->bi_ioc dereference in
rq_ioc() to fix build breakage.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Kent Overstreet <koverstreet@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Currently ioc->nr_tasks is used to decide two things - whether an ioc
is done issuing IOs and whether it's shared by multiple tasks. This
patch separate out the first into ioc->active_ref, which is acquired
and released using {get|put}_io_context_active() respectively.
This will be used to associate bio's with a given task. This patch
doesn't introduce any visible behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Make the following interface updates to prepare for future ioc related
changes.
* create_io_context() returning ioc only works for %current because it
doesn't increment ref on the ioc. Drop @task parameter from it and
always assume %current.
* Make create_io_context_slowpath() return 0 or -errno and rename it
to create_task_io_context().
* Make ioc_create_icq() take @ioc as parameter instead of assuming
that of %current. The caller, get_request(), is updated to create
ioc explicitly and then pass it into ioc_create_icq().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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get_request() is structured a bit unusually in that failure path is
inlined in the usual flow with goto labels atop and inside it.
Relocate the error path to the end of the function.
This is to prepare for icq handling changes in get_request() and
doesn't introduce any behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Now that blkg additions / removals are always done under both q and
blkcg locks, the only places RCU locking is necessary are
blkg_lookup[_create]() for lookup w/o blkcg lock. This patch drops
unncessary RCU locking replacing it with plain blkcg locking as
necessary.
* blkiocg_pre_destroy() already perform proper locking and don't need
RCU. Dropped.
* blkio_read_blkg_stats() now uses blkcg->lock instead of RCU read
lock. This isn't a hot path.
* Now unnecessary synchronize_rcu() from queue exit paths removed.
This makes q->nr_blkgs unnecessary. Dropped.
* RCU annotation on blkg->q removed.
-v2: Vivek pointed out that blkg_lookup_create() still needs to be
called under rcu_read_lock(). Updated.
-v3: After the update, stats_lock locking in blkio_read_blkg_stats()
shouldn't be using _irq variant as it otherwise ends up enabling
irq while blkcg->lock is locked. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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