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>
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>
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>
Pull block core bits from Jens Axboe:
"It's a nice and quiet round this time, since most of the tricky stuff
has been pushed to 3.5 to give it more time to mature. After a few
hectic block IO core changes for 3.3 and 3.2, I'm quite happy with a
slow round.
Really minor stuff in here, the only real functional change is making
the auto-unplug threshold a per-queue entity. The threshold is set so
that it's low enough that we don't hold off IO for too long, but still
big enough to get a nice benefit from the batched insert (and hence
queue lock cost reduction). For raid configurations, this currently
breaks down."
* 'for-3.4/core' of git://git.kernel.dk/linux-block:
block: make auto block plug flush threshold per-disk based
Documentation: Add sysfs ABI change for cfq's target latency.
block: Make cfq_target_latency tunable through sysfs.
block: use lockdep_assert_held for queue locking
block: blk_alloc_queue_node(): use caller's GFP flags instead of GFP_KERNEL
We do auto block plug flush to reduce latency, the threshold is 16
requests. This works well if the task is accessing one or two drives.
The problem is if the task is accessing a raid 0 device and the raid
disk number is big, say 8 or 16, 16/8 = 2 or 16/16=1, we will have
heavy lock contention.
This patch makes the threshold per-disk based. The latency should be
still ok accessing one or two drives. The setup with application
accessing a lot of drives in the meantime uaually is big machine,
avoiding lock contention is more important, because any contention
will actually increase latency.
Signed-off-by: Shaohua Li <shli@fusionio.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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
In cfq, when we calculate a time slice for a process(or a cfqq to
be precise), we have to consider the cfq_target_latency so that all the
sync request have an estimated latency(300ms) and it is controlled by
cfq_target_latency. But in some hadoop test, we have found that if
there are many processes doing sequential read(24 for example), the
throughput is bad because every process can only work for about 25ms
and the cfqq is switched. That leads to a higher disk seek. We can
achive the good throughput by setting low_latency=0, but then some
read's latency is too much for the application.
So this patch makes cfq_target_latency tunable through sysfs so that
we can tune it and find some magic number which is not bad for both
the throughput and the read latency.
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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>
Convert debug, freezer, cpuset, cpu_cgroup, cpuacct, net_prio, blkio,
net_cls and device controllers to use the new cftype based interface.
Termination entry is added to cftype arrays and populate callbacks are
replaced with cgroup_subsys->base_cftypes initializations.
This is functionally identical transformation. There shouldn't be any
visible behavior change.
memcg is rather special and will be converted separately.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <paul@paulmenage.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
blk-cgroup, netprio_cgroup, cls_cgroup and tcp_memcontrol
unnecessarily define cftype array and cgroup_subsys structures at the
top of the file, which is unconventional and necessiates forward
declaration of methods.
This patch relocates those below the definitions of the methods and
removes the forward declarations. Note that forward declaration of
tcp_files[] is added in tcp_memcontrol.c for tcp_init_cgroup(). This
will be removed soon by another patch.
This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
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>
We should use the GFP flags that the caller specified instead of picking
our own. All the callers specify GFP_KERNEL so this doesn't make a
difference to how the kernel runs, it's just a cleanup.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pull cgroup changes from Tejun Heo:
"Out of the 8 commits, one fixes a long-standing locking issue around
tasklist walking and others are cleanups."
* 'for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: Walk task list under tasklist_lock in cgroup_enable_task_cg_list
cgroup: Remove wrong comment on cgroup_enable_task_cg_list()
cgroup: remove cgroup_subsys argument from callbacks
cgroup: remove extra calls to find_existing_css_set
cgroup: replace tasklist_lock with rcu_read_lock
cgroup: simplify double-check locking in cgroup_attach_proc
cgroup: move struct cgroup_pidlist out from the header file
cgroup: remove cgroup_attach_task_current_cg()
Pull scheduler changes for v3.4 from Ingo Molnar
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
printk: Make it compile with !CONFIG_PRINTK
sched/x86: Fix overflow in cyc2ns_offset
sched: Fix nohz load accounting -- again!
sched: Update yield() docs
printk/sched: Introduce special printk_sched() for those awkward moments
sched/nohz: Correctly initialize 'next_balance' in 'nohz' idle balancer
sched: Cleanup cpu_active madness
sched: Fix load-balance wreckage
sched: Clean up parameter passing of proc_sched_autogroup_set_nice()
sched: Ditch per cgroup task lists for load-balancing
sched: Rename load-balancing fields
sched: Move load-balancing arguments into helper struct
sched/rt: Do not submit new work when PI-blocked
sched/rt: Prevent idle task boosting
sched/wait: Add __wake_up_all_locked() API
sched/rt: Document scheduler related skip-resched-check sites
sched/rt: Use schedule_preempt_disabled()
sched/rt: Add schedule_preempt_disabled()
sched/rt: Do not throttle when PI boosting
sched/rt: Keep period timer ticking when rt throttling is active
...
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>
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>
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>
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>
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>
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>
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>
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>
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>
Pull block fixes from Jens Axboe:
"Been sitting on this for a while, but lets get this out the door.
This fixes various important bugs for 3.3 final, along with a few more
trivial ones. Please pull!"
* 'for-linus' of git://git.kernel.dk/linux-block:
block: fix ioc leak in put_io_context
block, sx8: fix pointer math issue getting fw version
Block: use a freezable workqueue for disk-event polling
drivers/block/DAC960: fix -Wuninitialized warning
drivers/block/DAC960: fix DAC960_V2_IOCTL_Opcode_T -Wenum-compare warning
block: fix __blkdev_get and add_disk race condition
block: Fix setting bio flags in drivers (sd_dif/floppy)
block: Fix NULL pointer dereference in sd_revalidate_disk
block: exit_io_context() should call elevator_exit_icq_fn()
block: simplify ioc_release_fn()
block: replace icq->changed with icq->flags
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>
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>
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>
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>
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>
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>
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>
blkgs are chained from both blkcgs and request_queues and thus
subjected to two locks - blkcg->lock and q->queue_lock. As both blkcg
and q can go away anytime, locking during removal is tricky. It's
currently solved by wrapping removal inside RCU, which makes the
synchronization complex. There are three locks to worry about - the
outer RCU, q lock and blkcg lock, and it leads to nasty subtle
complications like conditional synchronize_rcu() on queue exit paths.
For all other paths, blkcg lock is naturally nested inside q lock and
the only exception is blkcg removal path, which is a very cold path
and can be implemented as clumsy but conceptually-simple reverse
double lock dancing.
This patch updates blkg removal path such that blkgs are removed while
holding both q and blkcg locks, which is trivial for request queue
exit path - blkg_destroy_all(). The blkcg removal path,
blkiocg_pre_destroy(), implements reverse double lock dancing
essentially identical to ioc_release_fn().
This simplifies blkg locking - no half-dead blkgs to worry about. Now
unnecessary RCU annotations will be removed by the next patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, blkg is per cgroup-queue-policy combination. This is
unnatural and leads to various convolutions in partially used
duplicate fields in blkg, config / stat access, and general management
of blkgs.
This patch make blkg's per cgroup-queue and let them serve all
policies. blkgs are now created and destroyed by blkcg core proper.
This will allow further consolidation of common management logic into
blkcg core and API with better defined semantics and layering.
As a transitional step to untangle blkg management, elvswitch and
policy [de]registration, all blkgs except the root blkg are being shot
down during elvswitch and bypass. This patch adds blkg_root_update()
to update root blkg in place on policy change. This is hacky and racy
but should be good enough as interim step until we get locking
simplified and switch over to proper in-place update for all blkgs.
-v2: Root blkgs need to be updated on elvswitch too and blkg_alloc()
comment wasn't updated according to the function change. Fixed.
Both pointed out by Vivek.
-v3: v2 updated blkg_destroy_all() to invoke update_root_blkg_pd() for
all policies. This freed root pd during elvswitch before the
last queue finished exiting and led to oops. Directly invoke
update_root_blkg_pd() only on BLKIO_POLICY_PROP from
cfq_exit_queue(). This also is closer to what will be done with
proper in-place blkg update. Reported by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With the previous patch to move blkg list heads and counters to
request_queue and blkg, logic to manage them in both policies are
almost identical and can be moved to blkcg core.
This patch moves blkg link logic into blkg_lookup_create(), implements
common blkg unlink code in blkg_destroy(), and updates
blkg_destory_all() so that it's policy specific and can skip root
group. The updated blkg_destroy_all() is now used to both clear queue
for bypassing and elv switching, and release all blkgs on q exit.
This patch introduces a race window where policy [de]registration may
race against queue blkg clearing. This can only be a problem on cfq
unload and shouldn't be a real problem in practice (and we have many
other places where this race already exists). Future patches will
remove these unlikely races.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, specific policy implementations are responsible for
maintaining list and number of blkgs. This duplicates code
unnecessarily, and hinders factoring common code and providing blkcg
API with better defined semantics.
After this patch, request_queue hosts list heads and counters and blkg
has list nodes for both policies. This patch only relocates the
necessary fields and the next patch will actually move management code
into blkcg core.
Note that request_queue->blkg_list[] and ->nr_blkgs[] are hardcoded to
have 2 elements. This is to avoid include dependency and will be
removed by the next patch.
This patch doesn't introduce any behavior change.
-v2: Now unnecessary conditional on CONFIG_BLK_CGROUP_MODULE removed
as 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>
blkg is scheduled to be unified for all policies and thus there won't
be one-to-one mapping from blkg to policy. Update stat related
functions to take explicit @pol or @plid arguments and not use
blkg->plid.
This is painful for now but most of specific stat interface functions
will be replaced with a handful of generic helpers.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
To prepare for unifying blkgs for different policies, make blkg->pd an
array with BLKIO_NR_POLICIES elements and move blkg->conf, ->stats,
and ->stats_cpu into blkg_policy_data.
This patch doesn't introduce 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>
Currently, blkcg policy implementations manage blkg refcnt duplicating
mostly identical code in both policies. This patch moves refcnt to
blkg and let blkcg core handle refcnt and freeing of blkgs.
* cfq blkgs now also get freed via RCU.
* cfq blkgs lose RB_EMPTY_ROOT() sanity check on blkg free. If
necessary, we can add blkio_exit_group_fn() to resurrect this.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, blkg's are embedded in private data blkcg policy private
data structure and thus allocated and freed by policies. This leads
to duplicate codes in policies, hinders implementing common part in
blkcg core with strong semantics, and forces duplicate blkg's for the
same cgroup-q association.
This patch introduces struct blkg_policy_data which is a separate data
structure chained from blkg. Policies specifies the amount of private
data it needs in its blkio_policy_type->pdata_size and blkcg core
takes care of allocating them along with blkg which can be accessed
using blkg_to_pdata(). blkg can be determined from pdata using
pdata_to_blkg(). blkio_alloc_group_fn() method is accordingly updated
to blkio_init_group_fn().
For consistency, tg_of_blkg() and cfqg_of_blkg() are replaced with
blkg_to_tg() and blkg_to_cfqg() respectively, and functions to map in
the reverse direction are added.
Except that policy specific data now lives in a separate data
structure from blkg, this patch doesn't introduce any functional
difference.
This will be used to unify blkg's for different policies.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Keep track of all request_queues which have blkcg initialized and turn
on bypass and invoke blkcg_clear_queue() on all before making changes
to blkcg policies.
This is to prepare for moving blkg management into blkcg core. Note
that this uses more brute force than necessary. Finer grained shoot
down will be implemented later and given that policy [un]registration
almost never happens on running systems (blk-throtl can't be built as
a module and cfq usually is the builtin default iosched), this
shouldn't be a problem for the time being.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently block core calls directly into blk-throttle for init, drain
and exit. This patch adds blkcg_{init|drain|exit}_queue() which wraps
the blk-throttle functions. This is to give more control and
visiblity to blkcg core layer for proper layering. Further patches
will add logic common to blkcg policies to the functions.
While at it, collapse blk_throtl_release() into blk_throtl_exit().
There's no reason to keep them separate.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, blkg points to the associated blkcg via its css_id. This
unnecessarily complicates dereferencing blkcg. Let blkg hold a
reference to the associated blkcg and point directly to it and disable
css_id on blkio_subsys.
This change requires splitting blkiocg_destroy() into
blkiocg_pre_destroy() and blkiocg_destroy() so that all blkg's can be
destroyed and all the blkcg references held by them dropped during
cgroup removal.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk-cgroup printing code currently assumes that there is a device/disk
associated with every queue in the system, but modules like floppy,
can instantiate request queues without registering disk which can lead
to oops.
Skip the queue/blkg which don't have dev/disk associated with them.
-tj: Factored out backing_dev_info check into blkg_dev_name().
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkg->dev is dev_t recording the device number of the block device for
the associated request_queue. It is used to identify the associated
block device when printing out configuration or stats.
This is redundant to begin with. A blkg is an association between a
cgroup and a request_queue and it of course is possible to reach
request_queue from blkg and synchronization conventions are in place
for safe q dereferencing, so this shouldn't be necessary from the
beginning. Furthermore, it's initialized by sscanf()ing the device
name of backing_dev_info. The mind boggles.
Anyways, if blkg is visible under rcu lock, we *know* that the
associated request_queue hasn't gone away yet and its bdi is
registered and alive - blkg can't be created for request_queue which
hasn't been fully initialized and it can't go away before blkg is
removed.
Let stat and conf read functions get device name from
blkg->q->backing_dev_info.dev and pass it down to printing functions
and remove blkg->dev.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that blkcg configuration lives in blkg's, blkio_policy_node is no
longer necessary. Kill it.
blkio_policy_parse_and_set() now fails if invoked for missing device
and functions to print out configurations are updated to print from
blkg's.
cftype_blkg_same_policy() is dropped along with other policy functions
for consistency. Its one line is open coded in the only user -
blkio_read_blkg_stats().
-v2: Update to reflect the retry-on-bypass logic change of the
previous patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkcg is very peculiar in that it allows setting and remembering
configurations for non-existent devices by maintaining separate data
structures for configuration.
This behavior is completely out of the usual norms and outright
confusing; furthermore, it uses dev_t number to match the
configuration to devices, which is unpredictable to begin with and
becomes completely unuseable if EXT_DEVT is fully used.
It is wholely unnecessary - we already have fully functional userland
mechanism to program devices being hotplugged which has full access to
device identification, connection topology and filesystem information.
Add a new struct blkio_group_conf which contains all blkcg
configurations to blkio_group and let blkio_group, which can be
created iff the associated device exists and is removed when the
associated device goes away, carry all configurations.
Note that, after this patch, all newly created blkg's will always have
the default configuration (unlimited for throttling and blkcg's weight
for propio).
This patch makes blkio_policy_node meaningless but doesn't remove it.
The next patch will.
-v2: Updated to retry after short sleep if blkg lookup/creation failed
due to the queue being temporarily bypassed as indicated by
-EBUSY return. Pointed out by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently both blk-throttle and cfq-iosched implement their own
blkio_group creation code in throtl_get_tg() and cfq_get_cfqg(). This
patch factors out the common code into blkg_lookup_create(), which
returns ERR_PTR value so that transitional failures due to queue
bypass can be distinguished from other failures.
* New plkio_policy_ops methods blkio_alloc_group_fn() and
blkio_link_group_fn added. Both are transitional and will be
removed once the blkg management code is fully moved into
blk-cgroup.c.
* blkio_alloc_group_fn() allocates policy-specific blkg which is
usually a larger data structure with blkg as the first entry and
intiailizes it. Note that initialization of blkg proper, including
percpu stats, is responsibility of blk-cgroup proper.
Note that default config (weight, bps...) initialization is done
from this method; otherwise, we end up violating locking order
between blkcg and q locks via blkcg_get_CONF() functions.
* blkio_link_group_fn() is called under queue_lock and responsible for
linking the blkg to the queue. blkcg side is handled by blk-cgroup
proper.
* The common blkg creation function is named blkg_lookup_create() and
blkiocg_lookup_group() is renamed to blkg_lookup() for consistency.
Also, throtl / cfq related functions are similarly [re]named for
consistency.
This simplifies blkcg policy implementations and enables further
cleanup.
-v2: Vivek noticed that blkg_lookup_create() incorrectly tested
blk_queue_dead() instead of blk_queue_bypass() leading a user of
the function ending up creating a new blkg on bypassing queue.
This is a bug introduced while relocating bypass patches before
this one. Fixed.
-v3: ERR_PTR patch folded into this one. @for_root added to
blkg_lookup_create() to allow creating root group on a bypassed
queue during elevator switch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For root blkg, blk_throtl_init() was using throtl_alloc_tg()
explicitly and cfq_init_queue() was manually initializing embedded
cfqd->root_group, adding unnecessarily different code paths to blkg
handling.
Make both use the usual blkio_group get functions - throtl_get_tg()
and cfq_get_cfqg() - for the root blkio_group too. Note that
blk_throtl_init() callsite is pushed downwards in
blk_alloc_queue_node() so that @q is sufficiently initialized for
throtl_get_tg().
This simplifies root blkg handling noticeably for cfq and will allow
further modularization of blkcg API.
-v2: Vivek pointed out that using cfq_get_cfqg() won't work if
CONFIG_CFQ_GROUP_IOSCHED is disabled. Fix it by factoring out
initialization of base part of cfqg into cfq_init_cfqg_base() and
alloc/init/free explicitly if !CONFIG_CFQ_GROUP_IOSCHED.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Block cgroup policies are maintained in a linked list and,
theoretically, multiple policies sharing the same policy ID are
allowed.
This patch temporarily restricts one policy per plid and adds
blkio_policy[] array which indexes registered policy types by plid.
Both the restriction and blkio_policy[] array are transitional and
will be removed once API cleanup is complete.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkgio_group is association between a block cgroup and a queue for a
given policy. Using opaque void * for association makes things
confusing and hinders factoring of common code. Use request_queue *
and, if necessary, policy id instead.
This will help block cgroup API cleanup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In both blkg get functions - throtl_get_tg() and cfq_get_cfqg(),
instead of obtaining blkcg of %current explicitly, let the caller
specify the blkcg to use as parameter and make both functions hold on
to the blkcg.
This is part of block cgroup interface cleanup and will help making
blkcg API more modular.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
rcu_read_lock() in throtl_get_tb() and cfq_get_cfqg() holds onto
@blkcg while looking up blkg. For API cleanup, the next patch will
make the caller responsible for determining @blkcg to look blkg from
and let them specify it as a parameter. Move rcu read locking out to
the callers to prepare for the change.
-v2: Originally this patch was described as a fix for RCU read locking
bug around @blkg, which Vivek pointed out to be incorrect. It
was from misunderstanding the role of rcu locking as protecting
@blkg not @blkcg. Patch description updated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Elevator switch may involve changes to blkcg policies. Implement
shoot down of blkio_groups.
Combined with the previous bypass updates, the end goal is updating
blkcg core such that it can ensure that blkcg's being affected become
quiescent and don't have any per-blkg data hanging around before
commencing any policy updates. Until queues are made aware of the
policies that applies to them, as an interim step, all per-policy blkg
data will be shot down.
* blk-throtl doesn't need this change as it can't be disabled for a
live queue; however, update it anyway as the scheduled blkg
unification requires this behavior change. This means that
blk-throtl configuration will be unnecessarily lost over elevator
switch. This oddity will be removed after blkcg learns to associate
individual policies with request_queues.
* blk-throtl dosen't shoot down root_tg. This is to ease transition.
Unified blkg will always have persistent root group and not shooting
down root_tg for now eases transition to that point by avoiding
having to update td->root_tg and is safe as blk-throtl can never be
disabled
-v2: Vivek pointed out that group list is not guaranteed to be empty
on return from clear function if it raced cgroup removal and
lost. Fix it by waiting a bit and retrying. This kludge will
soon be removed once locking is updated such that blkg is never
in limbo state between blkcg and request_queue locks.
blk-throtl no longer shoots down root_tg to avoid breaking
td->root_tg.
Also, Nest queue_lock inside blkio_list_lock not the other way
around to avoid introduce possible deadlock via blkcg lock.
-v3: blkcg_clear_queue() repositioned and renamed to
blkg_destroy_all() to increase consistency with later changes.
cfq_clear_queue() updated to check q->elevator before
dereferencing it to avoid NULL dereference on not fully
initialized queues (used by later change).
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Extend queue bypassing such that dying queue is always bypassing and
blk-throttle is drained on bypass. With blkcg policies updated to
test blk_queue_bypass() instead of blk_queue_dead(), this ensures that
no bio or request is held by or going through blkcg policies on a
bypassing queue.
This will be used to implement blkg cleanup on elevator switches and
policy changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Rename and extend elv_queisce_start/end() to
blk_queue_bypass_start/end() which are exported and supports nesting
via @q->bypass_depth. Also add blk_queue_bypass() to test bypass
state.
This will be further extended and used for blkio_group management.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
elevator_ops->elevator_init_fn() has a weird return value. It returns
a void * which the caller should assign to q->elevator->elevator_data
and %NULL return denotes init failure.
Update such that it returns integer 0/-errno and sets elevator_data
directly as necessary.
This makes the interface more conventional and eases further cleanup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Elevator switch tries hard to keep as much as context until new
elevator is ready so that it can revert to the original state if
initializing the new elevator fails for some reason. Unfortunately,
with more auxiliary contexts to manage, this makes elevator init and
exit paths too complex and fragile.
This patch makes elevator_switch() unregister the current elevator and
flush icq's before start initializing the new one. As we still keep
the old elevator itself, the only difference is that we lose icq's on
rare occassions of switching failure, which isn't critical at all.
Note that this makes explicit elevator parameter to
elevator_init_queue() and __elv_register_queue() unnecessary as they
always can use the current elevator.
This patch enables block cgroup cleanups.
-v2: blk_add_trace_msg() prints elevator name from @new_e instead of
@e->type as the local variable no longer exists. This caused
build failure on CONFIG_BLK_DEV_IO_TRACE.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
cfq has been registering zeroed blkio_poilcy_cfq if CFQ_GROUP_IOSCHED
is disabled. This fortunately doesn't collide with blk-throtl as
BLKIO_POLICY_PROP is zero but is unnecessary and risky. Just don't
register it if not enabled.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Block cgroup core can be built as module; however, it isn't too useful
as blk-throttle can only be built-in and cfq-iosched is usually the
default built-in scheduler. Scheduled blkcg cleanup requires calling
into blkcg from block core. To simplify that, disallow building blkcg
as module by making CONFIG_BLK_CGROUP bool.
If building blkcg core as module really matters, which I doubt, we can
revisit it after blkcg API cleanup.
-v2: Vivek pointed out that IOSCHED_CFQ was incorrectly updated to
depend on BLK_CGROUP. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently, blk_cleanup_queue() doesn't call elv_drain_elevator() if
q->elevator doesn't exist; however, bio based drivers don't have
elevator initialized but can still use blk-throttle. This patch moves
q->elevator test inside blk_drain_queue() such that only
elv_drain_elevator() is skipped if !q->elevator.
-v2: loop can have registered queue which has NULL request_fn. Make
sure we don't call into __blk_run_queue() in such cases.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Vivek Goyal <vgoyal@redhat.com>
Fold in bug fix from Vivek.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This patch (as1519) fixes a bug in the block layer's disk-events
polling. The polling is done by a work routine queued on the
system_nrt_wq workqueue. Since that workqueue isn't freezable, the
polling continues even in the middle of a system sleep transition.
Obviously, polling a suspended drive for media changes and such isn't
a good thing to do; in the case of USB mass-storage devices it can
lead to real problems requiring device resets and even re-enumeration.
The patch fixes things by creating a new system-wide, non-reentrant,
freezable workqueue and using it for disk-events polling.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The following situation might occur:
__blkdev_get: add_disk:
register_disk()
get_gendisk()
disk_block_events()
disk->ev == NULL
disk_add_events()
__disk_unblock_events()
disk->ev != NULL
--ev->block
Then we unblock events, when they are suppose to be blocked. This can
trigger events related block/genhd.c warnings, but also can crash in
sd_check_events() or other places.
I'm able to reproduce crashes with the following scripts (with
connected usb dongle as sdb disk).
<snip>
DEV=/dev/sdb
ENABLE=/sys/bus/usb/devices/1-2/bConfigurationValue
function stop_me()
{
for i in `jobs -p` ; do kill $i 2> /dev/null ; done
exit
}
trap stop_me SIGHUP SIGINT SIGTERM
for ((i = 0; i < 10; i++)) ; do
while true; do fdisk -l $DEV 2>&1 > /dev/null ; done &
done
while true ; do
echo 1 > $ENABLE
sleep 1
echo 0 > $ENABLE
done
</snip>
I use the script to verify patch fixing oops in sd_revalidate_disk
http://marc.info/?l=linux-scsi&m=132935572512352&w=2
Without Jun'ichi Nomura patch titled "Fix NULL pointer dereference in
sd_revalidate_disk" or this one, script easily crash kernel within
a few seconds. With both patches applied I do not observe crash.
Unfortunately after some time (dozen of minutes), script will hung in:
[ 1563.906432] [<c08354f5>] schedule_timeout_uninterruptible+0x15/0x20
[ 1563.906437] [<c04532d5>] msleep+0x15/0x20
[ 1563.906443] [<c05d60b2>] blk_drain_queue+0x32/0xd0
[ 1563.906447] [<c05d6e00>] blk_cleanup_queue+0xd0/0x170
[ 1563.906454] [<c06d278f>] scsi_free_queue+0x3f/0x60
[ 1563.906459] [<c06d7e6e>] __scsi_remove_device+0x6e/0xb0
[ 1563.906463] [<c06d4aff>] scsi_forget_host+0x4f/0x60
[ 1563.906468] [<c06cd84a>] scsi_remove_host+0x5a/0xf0
[ 1563.906482] [<f7f030fb>] quiesce_and_remove_host+0x5b/0xa0 [usb_storage]
[ 1563.906490] [<f7f03203>] usb_stor_disconnect+0x13/0x20 [usb_storage]
Anyway I think this patch is some step forward.
As drawback, I do not teardown on sysfs file create error, because I do
not know how to nullify disk->ev (since it can be used). However add_disk
error handling practically does not exist too, and things will work
without this sysfs file, except events will not be exported to user
space.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since 2.6.39 (1196f8b), when a driver returns -ENOMEDIUM for open(),
__blkdev_get() calls rescan_partitions() to remove
in-kernel partition structures and raise KOBJ_CHANGE uevent.
However it ends up calling driver's revalidate_disk without open
and could cause oops.
In the case of SCSI:
process A process B
----------------------------------------------
sys_open
__blkdev_get
sd_open
returns -ENOMEDIUM
scsi_remove_device
<scsi_device torn down>
rescan_partitions
sd_revalidate_disk
<oops>
Oopses are reported here:
http://marc.info/?l=linux-scsi&m=132388619710052
This patch separates the partition invalidation from rescan_partitions()
and use it for -ENOMEDIUM case.
Reported-by: Huajun Li <huajun.li.lee@gmail.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
From: Ben Hutchings <ben@decadent.org.uk>
Extended VBLKs (those larger than the preset VBLK size) are divided
into fragments, each with its own VBLK header. Our LDM implementation
generally assumes that each VBLK is contiguous in memory, so these
fragments must be assembled before further processing.
Currently the reassembly seems to be done quite wrongly - no VBLK
header is copied into the contiguous buffer, and the length of the
header is subtracted twice from each fragment. Also the total
length of the reassembled VBLK is calculated incorrectly.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Anton Altaparmakov <anton@tuxera.com>
While updating locking, b2efa05265 "block, cfq: unlink
cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation
from exit_io_context() to the final ioc put. While this doesn't cause
catastrophic failure, it effectively removes task exit notification to
elevator and cause noticeable IO performance degradation with CFQ.
On task exit, CFQ used to immediately expire the slice if it was being
used by the exiting task as no more IO would be issued by the task;
however, after b2efa05265, the notification is lost and disk could sit
idle needlessly, leading to noticeable IO performance degradation for
certain workloads.
This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates
elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it
from exit_io_context(). ICQ_EXITED flag is added to avoid invoking
the callback more than once for the same icq.
Walking icq_list from ioc side and invoking elevator callback requires
reverse double locking. This may be better implemented using RCU;
unfortunately, using RCU isn't trivial. e.g. RCU protection would
need to cover request_queue and queue_lock switch on cleanup makes
grabbing queue_lock from RCU unsafe. Reverse double locking should
do, at least for now.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-bisected-by: Shaohua Li <shli@kernel.org>
LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com>
Tested-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Reverse double lock dancing in ioc_release_fn() can be simplified by
just using trylock on the queue_lock and back out from ioc lock on
trylock failure. Simplify it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
icq->changed was used for ICQ_*_CHANGED bits. Rename it to flags and
access it under ioc->lock instead of using atomic bitops.
ioc_get_changed() is added so that the changed part can be fetched and
cleared as before.
icq->flags will be used to carry other flags.
Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
11a3122f6c "block: strip out locking optimization in put_io_context()"
removed ioc_lock depth lockdep annoation along with locking
optimization; however, while recursing from put_io_context() is no
longer possible, ioc_release_fn() may still end up putting the last
reference of another ioc through elevator, which wlil grab ioc->lock
triggering spurious (as the ioc is always different one) A-A deadlock
warning.
As this can only happen one time from ioc_release_fn(), using non-zero
subclass from ioc_release_fn() is enough. Use subclass 1.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We create "bsg" link if q->kobj.sd is not NULL, so remove it only
when the same condition is true.
Fixes:
WARNING: at fs/sysfs/inode.c:323 sysfs_hash_and_remove+0x2b/0x77()
sysfs: can not remove 'bsg', no directory
Call Trace:
[<c0429683>] warn_slowpath_common+0x6a/0x7f
[<c0537a68>] ? sysfs_hash_and_remove+0x2b/0x77
[<c042970b>] warn_slowpath_fmt+0x2b/0x2f
[<c0537a68>] sysfs_hash_and_remove+0x2b/0x77
[<c053969a>] sysfs_remove_link+0x20/0x23
[<c05d88f1>] bsg_unregister_queue+0x40/0x6d
[<c0692263>] __scsi_remove_device+0x31/0x9d
[<c069149f>] scsi_forget_host+0x41/0x52
[<c0689fa9>] scsi_remove_host+0x71/0xe0
[<f7de5945>] quiesce_and_remove_host+0x51/0x83 [usb_storage]
[<f7de5a1e>] usb_stor_disconnect+0x18/0x22 [usb_storage]
[<c06c29de>] usb_unbind_interface+0x4e/0x109
[<c067a80f>] __device_release_driver+0x6b/0xa6
[<c067a861>] device_release_driver+0x17/0x22
[<c067a46a>] bus_remove_device+0xd6/0xe6
[<c06785e2>] device_del+0xf2/0x137
[<c06c101f>] usb_disable_device+0x94/0x1a0
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Plug merge calls two elevator callbacks outside queue lock -
elevator_allow_merge_fn() and elevator_bio_merged_fn(). Although
attempt_plug_merge() suggests that elevator is guaranteed to be there
through the existing request on the plug list, nothing prevents plug
merge from calling into dying or initializing elevator.
For regular merges, bypass ensures elvpriv count to reach zero, which
in turn prevents merges as all !ELVPRIV requests get REQ_SOFTBARRIER
from forced back insertion. Plug merge doesn't check ELVPRIV, and, as
the requests haven't gone through elevator insertion yet, it doesn't
have SOFTBARRIER set allowing merges on a bypassed queue.
This, for example, leads to the following crash during elevator
switch.
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: [<ffffffff813b34e9>] cfq_allow_merge+0x49/0xa0
PGD 112cbc067 PUD 115d5c067 PMD 0
Oops: 0000 [#1] PREEMPT SMP
CPU 1
Modules linked in: deadline_iosched
Pid: 819, comm: dd Not tainted 3.3.0-rc2-work+ #76 Bochs Bochs
RIP: 0010:[<ffffffff813b34e9>] [<ffffffff813b34e9>] cfq_allow_merge+0x49/0xa0
RSP: 0018:ffff8801143a38f8 EFLAGS: 00010297
RAX: 0000000000000000 RBX: ffff88011817ce28 RCX: ffff880116eb6cc0
RDX: 0000000000000000 RSI: ffff880118056e20 RDI: ffff8801199512f8
RBP: ffff8801143a3908 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff880118195708
R13: ffff880118052aa0 R14: ffff8801143a3d50 R15: ffff880118195708
FS: 00007f19f82cb700(0000) GS:ffff88011fc80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000008 CR3: 0000000112c6a000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process dd (pid: 819, threadinfo ffff8801143a2000, task ffff880116eb6cc0)
Stack:
ffff88011817ce28 ffff880118195708 ffff8801143a3928 ffffffff81391bba
ffff88011817ce28 ffff880118195708 ffff8801143a3948 ffffffff81391bf1
ffff88011817ce28 0000000000000000 ffff8801143a39a8 ffffffff81398e3e
Call Trace:
[<ffffffff81391bba>] elv_rq_merge_ok+0x4a/0x60
[<ffffffff81391bf1>] elv_try_merge+0x21/0x40
[<ffffffff81398e3e>] blk_queue_bio+0x8e/0x390
[<ffffffff81396a5a>] generic_make_request+0xca/0x100
[<ffffffff81396b04>] submit_bio+0x74/0x100
[<ffffffff811d45c2>] __blockdev_direct_IO+0x1ce2/0x3450
[<ffffffff811d0dc7>] blkdev_direct_IO+0x57/0x60
[<ffffffff811460b5>] generic_file_aio_read+0x6d5/0x760
[<ffffffff811986b2>] do_sync_read+0xe2/0x120
[<ffffffff81199345>] vfs_read+0xc5/0x180
[<ffffffff81199501>] sys_read+0x51/0x90
[<ffffffff81aeac12>] system_call_fastpath+0x16/0x1b
There are multiple ways to fix this including making plug merge check
ELVPRIV; however,
* Calling into elevator outside queue lock is confusing and
error-prone.
* Requests on plug list aren't known to the elevator. They aren't on
the elevator yet, so there's no elevator specific state to update.
* Given the nature of plug merges - collecting bio's for the same
purpose from the same issuer - elevator specific restrictions aren't
applicable.
So, simply don't call into elevator methods from plug merge by moving
elv_bio_merged() from bio_attempt_*_merge() to blk_queue_bio(), and
using blk_try_merge() in attempt_plug_merge().
This is based on Jens' patch to skip elevator_allow_merge_fn() from
plug merge.
Note that this makes per-cgroup merged stats skip plug merging.
Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <4F16F3CA.90904@kernel.dk>
Original-patch-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_rq_merge_ok() is the elevator-neutral part of merge eligibility
test. blk_try_merge() determines merge direction and expects the
caller to have tested elv_rq_merge_ok() previously.
elv_rq_merge_ok() now wraps blk_rq_merge_ok() and then calls
elv_iosched_allow_merge(). elv_try_merge() is removed and the two
callers are updated to call elv_rq_merge_ok() explicitly followed by
blk_try_merge(). While at it, make rq_merge_ok() functions return
bool.
This is to prepare for plug merge update and doesn't introduce any
behavior change.
This is based on Jens' patch to skip elevator_allow_merge_fn() from
plug merge.
Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <4F16F3CA.90904@kernel.dk>
Original-patch-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
put_io_context() performed a complex trylock dancing to avoid
deferring ioc release to workqueue. It was also broken on UP because
trylock was always assumed to succeed which resulted in unbalanced
preemption count.
While there are ways to fix the UP breakage, even the most
pathological microbench (forced ioc allocation and tight fork/exit
loop) fails to show any appreciable performance benefit of the
optimization. Strip it out. If there turns out to be workloads which
are affected by this change, simpler optimization from the discussion
thread can be applied later.
Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <1328514611.21268.66.camel@sli10-conroe>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Tejun Heo