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>
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>
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_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_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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
There are a number of QUEUE_FLAG_DEAD tests. Add blk_queue_dead()
macro and use it.
This patch doesn't introduce any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
request_queue is refcounted but actually depdends on lifetime
management from the queue owner - on blk_cleanup_queue(), block layer
expects that there's no request passing through request_queue and no
new one will.
This is fundamentally broken. The queue owner (e.g. SCSI layer)
doesn't have a way to know whether there are other active users before
calling blk_cleanup_queue() and other users (e.g. bsg) don't have any
guarantee that the queue is and would stay valid while it's holding a
reference.
With delay added in blk_queue_bio() before queue_lock is grabbed, the
following oops can be easily triggered when a device is removed with
in-flight IOs.
sd 0:0:1:0: [sdb] Stopping disk
ata1.01: disabled
general protection fault: 0000 [#1] PREEMPT SMP
CPU 2
Modules linked in:
Pid: 648, comm: test_rawio Not tainted 3.1.0-rc3-work+ #56 Bochs Bochs
RIP: 0010:[<ffffffff8137d651>] [<ffffffff8137d651>] elv_rqhash_find+0x61/0x100
...
Process test_rawio (pid: 648, threadinfo ffff880019efa000, task ffff880019ef8a80)
...
Call Trace:
[<ffffffff8137d774>] elv_merge+0x84/0xe0
[<ffffffff81385b54>] blk_queue_bio+0xf4/0x400
[<ffffffff813838ea>] generic_make_request+0xca/0x100
[<ffffffff81383994>] submit_bio+0x74/0x100
[<ffffffff811c53ec>] dio_bio_submit+0xbc/0xc0
[<ffffffff811c610e>] __blockdev_direct_IO+0x92e/0xb40
[<ffffffff811c39f7>] blkdev_direct_IO+0x57/0x60
[<ffffffff8113b1c5>] generic_file_aio_read+0x6d5/0x760
[<ffffffff8118c1ca>] do_sync_read+0xda/0x120
[<ffffffff8118ce55>] vfs_read+0xc5/0x180
[<ffffffff8118cfaa>] sys_pread64+0x9a/0xb0
[<ffffffff81afaf6b>] system_call_fastpath+0x16/0x1b
This happens because blk_queue_cleanup() destroys the queue and
elevator whether IOs are in progress or not and DEAD tests are
sprinkled in the request processing path without proper
synchronization.
Similar problem exists for blk-throtl. On queue cleanup, blk-throtl
is shutdown whether it has requests in it or not. Depending on
timing, it either oopses or throttled bios are lost putting tasks
which are waiting for bio completion into eternal D state.
The way it should work is having the usual clear distinction between
shutdown and release. Shutdown drains all currently pending requests,
marks the queue dead, and performs partial teardown of the now
unnecessary part of the queue. Even after shutdown is complete,
reference holders are still allowed to issue requests to the queue
although they will be immmediately failed. The rest of teardown
happens on release.
This patch makes the following changes to make blk_queue_cleanup()
behave as proper shutdown.
* QUEUE_FLAG_DEAD is now set while holding both q->exit_mutex and
queue_lock.
* Unsynchronized DEAD check in generic_make_request_checks() removed.
This couldn't make any meaningful difference as the queue could die
after the check.
* blk_drain_queue() updated such that it can drain all requests and is
now called during cleanup.
* blk_throtl updated such that it checks DEAD on grabbing queue_lock,
drains all throttled bios during cleanup and free td when queue is
released.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_throtl_bio() and throtl_get_tg() have rather unusual interface.
* throtl_get_tg() returns pointer to a valid tg or ERR_PTR(-ENODEV),
and drops queue_lock in the latter case. Different locking context
depending on return value is error-prone and DEAD state is scheduled
to be protected by queue_lock anyway. Move DEAD check inside
queue_lock and return valid tg or NULL.
* blk_throtl_bio() indicates return status both with its return value
and in/out param **@bio. The former is used to indicate whether
queue is found to be dead during throtl processing. The latter
whether the bio is throttled.
There's no point in returning DEAD check result from
blk_throtl_bio(). The queue can die after blk_throtl_bio() is
finished but before make_request_fn() grabs queue lock.
Make it take *@bio instead and return boolean result indicating
whether the request is throttled or not.
This patch doesn't cause any visible functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_get/put_queue() in scsi_cmd_ioctl() and throtl_get_tg() are
completely bogus. The caller must have a reference to the queue on
entry and taking an extra reference doesn't change anything.
For scsi_cmd_ioctl(), the only effect is that it ends up checking
QUEUE_FLAG_DEAD on entry; however, this is bogus as queue can die
right after blk_get_queue(). Dead queue should be and is handled in
request issue path (it's somewhat broken now but that's a separate
problem and doesn't affect this one much).
throtl_get_tg() incorrectly assumes that q is rcu freed. Also, it
doesn't check return value of blk_get_queue(). If the queue is
already dead, it ends up doing an extra put.
Drop them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_throtl interface is block internal and there's no reason to have
them in linux/blkdev.h. Move them to block/blk.h.
This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
read request is always sync. Using rw_is_sync() to determine
if a bio is sync.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
The total of two unsigned values should also be unsigned.
Update throtl_log output to unsigned.
Update total_nr_queued test to non-zero to be the
same as the other total_nr_queued tests.
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Use the compiler to verify format strings and arguments.
Fix fallout.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently we take a queue lock on each bio to check if there are any
throttling rules associated with the group and also update the stats.
Now access the group under rcu and update the stats without taking
the queue lock. Queue lock is taken only if there are throttling rules
associated with the group.
So the common case of root group when there are no rules, save
unnecessary pounding of request queue lock.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently we take blkg_stat lock for even updating the stats. So even if
a group has no throttling rules (common case for root group), we end
up taking blkg_lock, for updating the stats.
Make dispatch stats per cpu so that these can be updated without taking
blkg lock.
If cpu goes offline, these stats simply disappear. No protection has
been provided for that yet. Do we really need anything for that?
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Soon we will allow accessing a throtl_grp under rcu_read_lock(). Hence
start freeing up throtl_grp after one rcu grace period.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Use same helper function for root group as we use with dynamically
allocated groups to add it to various lists.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
A helper function for the code which is used at 2-3 places. Makes reading
code little easier.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently, we allocate root throtl_grp statically. But as we will be
introducing per cpu stat pointers and that will be allocated
dynamically even for root group, we might as well make whole root
throtl_grp allocation dynamic and treat it in same manner as other
groups.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currently, all the cfq_group or throtl_group allocations happen while
we are holding ->queue_lock and sleeping is not allowed.
Soon, we will move to per cpu stats and also need to allocate the
per group stats. As one can not call alloc_percpu() from atomic
context as it can sleep, we need to drop ->queue_lock, allocate the
group, retake the lock and continue processing.
In throttling code, I check the queue DEAD flag again to make sure
that driver did not call blk_cleanup_queue() in the mean time.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Group initialization code seems to be at two places. root group
initialization in blk_throtl_init() and dynamically allocated group
in throtl_find_alloc_tg(). Create a common function and use at both
the places.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Currentlly we first map the task to cgroup and then cgroup to
blkio_cgroup. There is a more direct way to get to blkio_cgroup
from task using task_subsys_state(). Use that.
The real reason for the fix is that it also avoids a race in generic
cgroup code. During remount/umount rebind_subsystems() is called and
it can do following with and rcu protection.
cgrp->subsys[i] = NULL;
That means if somebody got hold of cgroup under rcu and then it tried
to do cgroup->subsys[] to get to blkio_cgroup, it would get NULL which
is wrong. I was running into this race condition with ltp running on a
upstream derived kernel and that lead to crash.
So ideally we should also fix cgroup generic code to wait for rcu
grace period before setting pointer to NULL. Li Zefan is not very keen
on introducing synchronize_wait() as he thinks it will slow
down moun/remount/umount operations.
So for the time being atleast fix the kernel crash by taking a more
direct route to blkio_cgroup.
One tester had reported a crash while running LTP on a derived kernel
and with this fix crash is no more seen while the test has been
running for over 6 days.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Tejun Heo