* Rename blkcg->pd[] to blkcg->cpd[] so that cpd is consistently used
for blkcg_policy_data.
* Make blkcg_policy->cpd_init_fn() take blkcg_policy_data instead of
blkcg. This makes it consistent with blkg_policy_data methods and
to-be-added cpd alloc/free methods.
* blkcg_policy_data->blkcg and cpd_to_blkcg() added so that
cpd_init_fn() can determine the associated blkcg from
blkcg_policy_data.
v2: blkcg_policy_data->blkcg initializations were missing. Added.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The newly added ->pd_alloc_fn() and ->pd_free_fn() deal with pd
(blkg_policy_data) while the older ones use blkg (blkcg_gq). As using
blkg doesn't make sense for ->pd_alloc_fn() and after allocation pd
can always be mapped to blkg and given that these are policy-specific
methods, it makes sense to converge on pd.
This patch makes all methods deal with pd instead of blkg. Most
conversions are trivial. In blk-cgroup.c, a couple method invocation
sites now test whether pd exists instead of policy state for
consistency. This shouldn't cause any behavioral differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
With the recent addition of alloc and free methods, things became
messier. This patch reorganizes them according to the followings.
* ->pd_alloc_fn()
Responsible for allocation and static initializations - the ones
which can be done independent of where the pd might be attached.
* ->pd_init_fn()
Initializations which require the knowledge of where the pd is
attached.
* ->pd_free_fn()
The counter part of pd_alloc_fn(). Static de-init and freeing.
This leaves ->pd_exit_fn() without any users. Removed.
While at it, collapse an one liner function throtl_pd_exit(), which
has only one user, into its user.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
A blkg (blkcg_gq) represents the relationship between a cgroup and
request_queue. Each active policy has a pd (blkg_policy_data) on each
blkg. The pd's were allocated by blkcg core and each policy could
request to allocate extra space at the end by setting
blkcg_policy->pd_size larger than the size of pd.
This is a bit unusual but was done this way mostly to simplify error
handling and all the existing use cases could be handled this way;
however, this is becoming too restrictive now that percpu memory can
be allocated without blocking.
This introduces two new mandatory blkcg_policy methods - pd_alloc_fn()
and pd_free_fn() - which are used to allocate and release pd for a
given policy. As pd allocation is now done from policy side, it can
simply allocate a larger area which embeds pd at the beginning. This
change makes ->pd_size pointless. Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Up until now, all async IOs were queued to async queues which are
shared across the whole request_queue, which means that blkcg resource
control is completely void on async IOs including all writeback IOs.
It was done this way because writeback didn't support writeback and
there was no way of telling which writeback IO belonged to which
cgroup; however, writeback recently became cgroup aware and writeback
bio's are sent down properly tagged with the blkcg's to charge them
against.
This patch makes async cfq_queues per-cfq_cgroup instead of
per-cfq_data so that each async IO is charged to the blkcg that it was
tagged for instead of unconditionally attributing it to root.
* cfq_data->async_cfqq and ->async_idle_cfqq are moved to cfq_group
and alloc / destroy paths are updated accordingly.
* cfq_link_cfqq_cfqg() no longer overrides @cfqg to root for async
queues.
* check_blkcg_changed() now also invalidates async queues as they no
longer stay the same across cgroups.
After this patch, cfq's proportional IO control through blkio.weight
works correctly when cgroup writeback is in use.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
cfq_find_alloc_queue() checks whether a queue actually needs to be
allocated, which is unnecessary as its sole caller, cfq_get_queue(),
only calls it if so. Also, the oom queue fallback logic is scattered
between cfq_get_queue() and cfq_find_alloc_queue(). There really
isn't much going on in the latter and things can be made simpler by
folding it into cfq_get_queue().
This patch collapses cfq_find_alloc_queue() into cfq_get_queue(). The
change is fairly straight-forward with one exception - async_cfqq is
now initialized to NULL and the "!is_sync" test in the last if
conditional is replaced with "async_cfqq" test. This is because gcc
(5.1.1) gets confused for some reason and warns that async_cfqq may be
used uninitialized otherwise. Oh well, the code isn't necessarily
worse this way.
This patch doesn't cause any functional difference.
v2: Updated to reflect GFP_ATOMIC -> GPF_NOWAIT.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This is necessary for making async cfq_cgroups per-cfq_group instead
of per-cfq_data. While this change makes cfq_get_queue() perform RCU
locking and look up cfq_group even when it reuses async queue, the
extra overhead is extremely unlikely to be noticeable given that this
is already sitting behind cic->cfqq[] cache and the overall cost of
cfq operation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Even when allocations fail, cfq_find_alloc_queue() always returns a
valid cfq_queue by falling back to the oom cfq_queue. As such, there
isn't much point in taking @gfp_mask and trying "harder" if __GFP_WAIT
is set. GFP_NOWAIT allocations don't fail often and even when they do
the degraded behavior is acceptable and temporary.
After all, the only reason get_request(), which ultimately determines
the gfp_mask, cares about __GFP_WAIT is to guarantee request
allocation, assuming IO forward progress, for callers which are
willing to wait. There's no reason for cfq_find_alloc_queue() to
behave differently on __GFP_WAIT when it already has a fallback
mechanism.
Remove @gfp_mask from cfq_find_alloc_queue() and propagate the changes
to its callers. This simplifies the function quite a bit and will
help making async queues per-cfq_group.
v2: Updated to reflect GFP_ATOMIC -> GPF_NOWAIT.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
blkcg performs several allocations to track IOs per cgroup and enforce
resource control. Most of these allocations are performed lazily on
demand in the IO path and thus can't involve reclaim path. Currently,
these allocations use GFP_ATOMIC; however, blkcg can gracefully deal
with occassional failures of these allocations by punting IOs to the
root cgroup and there's no reason to reach into the emergency reserve.
This patch replaces GFP_ATOMIC with GFP_NOWAIT for the following
allocations.
* bdi_writeback_congested and blkcg_gq allocations in blkg_create().
* radix tree node allocations for blkcg->blkg_tree.
* cfq_queue allocation on ioprio changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-and-Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Suggested-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
* Some were accessing cic->cfqq[] directly. Always use cic_to_cfqq()
and cic_set_cfqq().
* check_ioprio_changed() doesn't need to verify cfq_get_queue()'s
return for NULL. It's always non-NULL. Simplify accordingly.
This patch doesn't cause any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
If the cfq_queue cached in cfq_io_cq is the oom one, cfq_set_request()
replaces it by invoking cfq_get_queue() again without putting the oom
queue leaking the reference it was holding. While oom queues are not
released through reference counting, they're still reference counted
and this can theoretically lead to the reference count overflowing and
incorrectly invoke the usual release path on it.
Fix it by making cfq_set_request() put the ref it was holding.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Async cfqq's (cfq_queue's) are shared across cfq_data. When
cfq_get_queue() obtains a new queue from cfq_find_alloc_queue(), it
stashes the pointer in cfq_data and reuses it from then on; however,
the function doesn't consider that cfq_find_alloc_queue() may return
the oom_cfqq under memory pressure and installs the returned queue
unconditionally.
If the oom_cfqq is installed as an async cfqq, cfq_set_request() will
continue calling cfq_get_queue() hoping to replace it with a proper
queue; however, cfq_get_queue() will keep returning the cached queue
for the slot - the oom_cfqq.
Fix it by skipping caching if the queue is the oom one.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
cfq_get_queue()'s control flow looks like the following.
async_cfqq = NULL;
cfqq = NULL;
if (!is_sync) {
...
async_cfqq = ...;
cfqq = *async_cfqq;
}
if (!cfqq)
cfqq = ...;
if (!is_sync && !(*async_cfqq))
...;
The only thing the local variable init, the second if, and the
async_cfqq test in the third if achieves is to skip cfqq creation and
installation if *async_cfqq was already non-NULL. This is needlessly
complicated with different tests examining the same condition.
Simplify it to the following.
if (!is_sync) {
...
async_cfqq = ...;
cfqq = *async_cfqq;
if (cfqq)
goto out;
}
cfqq = ...;
if (!is_sync)
...;
out:
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Pull cgroup writeback support from Jens Axboe:
"This is the big pull request for adding cgroup writeback support.
This code has been in development for a long time, and it has been
simmering in for-next for a good chunk of this cycle too. This is one
of those problems that has been talked about for at least half a
decade, finally there's a solution and code to go with it.
Also see last weeks writeup on LWN:
http://lwn.net/Articles/648292/"
* 'for-4.2/writeback' of git://git.kernel.dk/linux-block: (85 commits)
writeback, blkio: add documentation for cgroup writeback support
vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB
writeback: do foreign inode detection iff cgroup writeback is enabled
v9fs: fix error handling in v9fs_session_init()
bdi: fix wrong error return value in cgwb_create()
buffer: remove unusued 'ret' variable
writeback: disassociate inodes from dying bdi_writebacks
writeback: implement foreign cgroup inode bdi_writeback switching
writeback: add lockdep annotation to inode_to_wb()
writeback: use unlocked_inode_to_wb transaction in inode_congested()
writeback: implement unlocked_inode_to_wb transaction and use it for stat updates
writeback: implement [locked_]inode_to_wb_and_lock_list()
writeback: implement foreign cgroup inode detection
writeback: make writeback_control track the inode being written back
writeback: relocate wb[_try]_get(), wb_put(), inode_{attach|detach}_wb()
mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use
writeback: implement memcg writeback domain based throttling
writeback: reset wb_domain->dirty_limit[_tstmp] when memcg domain size changes
writeback: implement memcg wb_domain
writeback: update wb_over_bg_thresh() to use wb_domain aware operations
...
Commit 9470e4a693 only covered the initial bug report, there are
other spots in CFQ where we need to check that we actually have
a valid cfq_group_data structure.
Fixes: e48453c3 ("block, cgroup: implement policy-specific per-blkcg data")
Signed-off-by: Jens Axboe <axboe@fb.com>
If none of the devices in the system are using CFQ, then attempting to
read:
/sys/fs/cgroup/blkio/blkio.leaf_weight
will results in a NULL dereference. Check for a valid cfq_group_data
struct before attempting to dereference it.
Reported-by: Andrey Wagin <avagin@gmail.com>
Fixes: e48453c3 ("block, cgroup: implement policy-specific per-blkcg data")
Signed-off-by: Jens Axboe <axboe@fb.com>
If CFQ_GROUP_IOSCHED is not set, the compiler produces the
following warning:
CC block/cfq-iosched.o
linux/block/cfq-iosched.c:469:2:
warning: 'cpd_to_cfqgd' defined but not used [-Wunused-function]
*cpd_to_cfqgd(struct blkcg_policy_data *cpd)
^
In reality, two other lookup functions aren't used either if
CFQ_GROUP_IOSCHED isn't set. Move all three under one of the
CFQ_GROUP_IOSCHED sections in the code.
Reported-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
A previous commit wanted to make CFQ default to IOPS mode on
non-rotational storage, however it did so when the queue was
initialized and the non-rotational flag is only set later on
in the probe.
Add an elevator hook that gets called off the add_disk() path,
at that point we know that feature probing has finished, and
we can reliably check for the various flags that drivers can
set.
Fixes: 41c0126b ("block: Make CFQ default to IOPS mode on SSDs")
Tested-by: Romain Francoise <romain@orebokech.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The block IO (blkio) controller enables the block layer to provide service
guarantees in a hierarchical fashion. Specifically, service guarantees
are provided by registered request-accounting policies. As of now, a
proportional-share and a throttling policy are available. They are
implemented, respectively, by the CFQ I/O scheduler and the blk-throttle
subsystem. Unfortunately, as for adding new policies, the current
implementation of the block IO controller is only halfway ready to allow
new policies to be plugged in. This commit provides a solution to make
the block IO controller fully ready to handle new policies.
In what follows, we first describe briefly the current state, and then
list the changes made by this commit.
The throttling policy does not need any per-cgroup information to perform
its task. In contrast, the proportional share policy uses, for each cgroup,
both the weight assigned by the user to the cgroup, and a set of dynamically-
computed weights, one for each device.
The first, user-defined weight is stored in the blkcg data structure: the
block IO controller allocates a private blkcg data structure for each
cgroup in the blkio cgroups hierarchy (regardless of which policy is active).
In other words, the block IO controller internally mirrors the blkio cgroups
with private blkcg data structures.
On the other hand, for each cgroup and device, the corresponding dynamically-
computed weight is maintained in the following, different way. For each device,
the block IO controller keeps a private blkcg_gq structure for each cgroup in
blkio. In other words, block IO also keeps one private mirror copy of the blkio
cgroups hierarchy for each device, made of blkcg_gq structures.
Each blkcg_gq structure keeps per-policy information in a generic array of
dynamically-allocated 'dedicated' data structures, one for each registered
policy (so currently the array contains two elements). To be inserted into the
generic array, each dedicated data structure embeds a generic blkg_policy_data
structure. Consider now the array contained in the blkcg_gq structure
corresponding to a given pair of cgroup and device: one of the elements
of the array contains the dedicated data structure for the proportional-share
policy, and this dedicated data structure contains the dynamically-computed
weight for that pair of cgroup and device.
The generic strategy adopted for storing per-policy data in blkcg_gq structures
is already capable of handling new policies, whereas the one adopted with blkcg
structures is not, because per-policy data are hard-coded in the blkcg
structures themselves (currently only data related to the proportional-
share policy).
This commit addresses the above issues through the following changes:
. It generalizes blkcg structures so that per-policy data are stored in the same
way as in blkcg_gq structures.
Specifically, it lets also the blkcg structure store per-policy data in a
generic array of dynamically-allocated dedicated data structures. We will
refer to these data structures as blkcg dedicated data structures, to
distinguish them from the dedicated data structures inserted in the generic
arrays kept by blkcg_gq structures.
To allow blkcg dedicated data structures to be inserted in the generic array
inside a blkcg structure, this commit also introduces a new blkcg_policy_data
structure, which is the equivalent of blkg_policy_data for blkcg dedicated
data structures.
. It adds to the blkcg_policy structure, i.e., to the descriptor of a policy, a
cpd_size field and a cpd_init field, to be initialized by the policy with,
respectively, the size of the blkcg dedicated data structures, and the
address of a constructor function for blkcg dedicated data structures.
. It moves the CFQ-specific fields embedded in the blkcg data structure (i.e.,
the fields related to the proportional-share policy), into a new blkcg
dedicated data structure called cfq_group_data.
Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
CFQ idling causes reduced IOPS throughput on non-rotational disks.
Since disk head seeking is not applicable to SSDs, it doesn't really
help performance by anticipating future near-by IO requests.
By turning off idling (and switching to IOPS mode), we allow other
processes to dispatch IO requests down to the driver and so increase IO
throughput.
Following FIO benchmark results were taken on a cloud SSD offering with
idling on and off:
Idling iops avg-lat(ms) stddev bw
------------------------------------------------------
On 7054 90.107 38.697 28217KB/s
Off 29255 21.836 11.730 117022KB/s
fio --name=temp --size=100G --time_based --ioengine=libaio \
--randrepeat=0 --direct=1 --invalidate=1 --verify=0 \
--verify_fatal=0 --rw=randread --blocksize=4k --group_reporting=1 \
--filename=/dev/sdb --runtime=10 --iodepth=64 --numjobs=10
And the following is from a local SSD run:
Idling iops avg-lat(ms) stddev bw
------------------------------------------------------
On 19320 33.043 14.068 77281KB/s
Off 21626 29.465 12.662 86507KB/s
fio --name=temp --size=5G --time_based --ioengine=libaio \
--randrepeat=0 --direct=1 --invalidate=1 --verify=0 \
--verify_fatal=0 --rw=randread --blocksize=4k --group_reporting=1 \
--filename=/fio_data --runtime=10 --iodepth=64 --numjobs=10
Reviewed-by: Nauman Rafique <nauman@google.com>
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
cgroup aware writeback support will require exposing some of blkcg
details. In preprataion, move block/blk-cgroup.h to
include/linux/blk-cgroup.h. This patch is pure file move.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Cfq_lookup_create_cfqg() allocates struct blkcg_gq using GFP_ATOMIC.
In cfq_find_alloc_queue() possible allocation failure is not handled.
As a result kernel oopses on NULL pointer dereference when
cfq_link_cfqq_cfqg() calls cfqg_get() for NULL pointer.
Bug was introduced in v3.5 in commit cd1604fab4 ("blkcg: factor
out blkio_group creation"). Prior to that commit cfq group lookup
had returned pointer to root group as fallback.
This patch handles this error using existing fallback oom_cfqq.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Fixes: cd1604fab4 ("blkcg: factor out blkio_group creation")
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>
Hi,
If you can manage to submit an async write as the first async I/O from
the context of a process with realtime scheduling priority, then a
cfq_queue is allocated, but filed into the wrong async_cfqq bucket. It
ends up in the best effort array, but actually has realtime I/O
scheduling priority set in cfqq->ioprio.
The reason is that cfq_get_queue assumes the default scheduling class and
priority when there is no information present (i.e. when the async cfqq
is created):
static struct cfq_queue *
cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
struct bio *bio, gfp_t gfp_mask)
{
const int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
const int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
cic->ioprio starts out as 0, which is "invalid". So, class of 0
(IOPRIO_CLASS_NONE) is passed to cfq_async_queue_prio like so:
async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
static struct cfq_queue **
cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
{
switch (ioprio_class) {
case IOPRIO_CLASS_RT:
return &cfqd->async_cfqq[0][ioprio];
case IOPRIO_CLASS_NONE:
ioprio = IOPRIO_NORM;
/* fall through */
case IOPRIO_CLASS_BE:
return &cfqd->async_cfqq[1][ioprio];
case IOPRIO_CLASS_IDLE:
return &cfqd->async_idle_cfqq;
default:
BUG();
}
}
Here, instead of returning a class mapped from the process' scheduling
priority, we get back the bucket associated with IOPRIO_CLASS_BE.
Now, there is no queue allocated there yet, so we create it:
cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic, bio, gfp_mask);
That function ends up doing this:
cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
cfq_init_prio_data(cfqq, cic);
cfq_init_cfqq marks the priority as having changed. Then, cfq_init_prio
data does this:
ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
switch (ioprio_class) {
default:
printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
case IOPRIO_CLASS_NONE:
/*
* no prio set, inherit CPU scheduling settings
*/
cfqq->ioprio = task_nice_ioprio(tsk);
cfqq->ioprio_class = task_nice_ioclass(tsk);
break;
So we basically have two code paths that treat IOPRIO_CLASS_NONE
differently, which results in an RT async cfqq filed into a best effort
bucket.
Attached is a patch which fixes the problem. I'm not sure how to make
it cleaner. Suggestions would be welcome.
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Tested-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>
A bit of churn on the for-linus side that would be nice to have
in the core bits for 3.18, so pull it in to catch us up and make
forward progress easier.
Signed-off-by: Jens Axboe <axboe@fb.com>
Conflicts:
block/scsi_ioctl.c
blkcg->id is a unique id given to each blkcg; however, the
cgroup_subsys_state which each blkcg embeds already has ->serial_nr
which can be used for the same purpose. Drop blkcg->id and replace
its uses with blkcg->css.serial_nr. Rename cfq_cgroup->blkcg_id to
->blkcg_serial_nr and @id in check_blkcg_changed() to @serial_nr for
consistency.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Explain that weight has to be updated on activation.
This complements previous fix e15693ef18 ("cfq-iosched: Fix wrong
children_weight calculation").
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <axboe@fb.com>
cfq_group_service_tree_add() is applying new_weight at the beginning of
the function via cfq_update_group_weight().
This actually allows weight to change between adding it to and subtracting
it from children_weight, and triggers WARN_ON_ONCE() in
cfq_group_service_tree_del(), or even causes oops by divide error during
vfr calculation in cfq_group_service_tree_add().
The detailed scenario is as follows:
1. Create blkio cgroups X and Y as a child of X.
Set X's weight to 500 and perform some I/O to apply new_weight.
This X's I/O completes before starting Y's I/O.
2. Y starts I/O and cfq_group_service_tree_add() is called with Y.
3. cfq_group_service_tree_add() walks up the tree during children_weight
calculation and adds parent X's weight (500) to children_weight of root.
children_weight becomes 500.
4. Set X's weight to 1000.
5. X starts I/O and cfq_group_service_tree_add() is called with X.
6. cfq_group_service_tree_add() applies its new_weight (1000).
7. I/O of Y completes and cfq_group_service_tree_del() is called with Y.
8. I/O of X completes and cfq_group_service_tree_del() is called with X.
9. cfq_group_service_tree_del() subtracts X's weight (1000) from
children_weight of root. children_weight becomes -500.
This triggers WARN_ON_ONCE().
10. Set X's weight to 500.
11. X starts I/O and cfq_group_service_tree_add() is called with X.
12. cfq_group_service_tree_add() applies its new_weight (500) and adds it
to children_weight of root. children_weight becomes 0. Calcularion of
vfr triggers oops by divide error.
weight should be updated right before adding it to children_weight.
Reported-by: Ruki Sekiya <sekiya.ruki@lab.ntt.co.jp>
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>
Pull cgroup updates from Tejun Heo:
"A lot of activities on cgroup side. Heavy restructuring including
locking simplification took place to improve the code base and enable
implementation of the unified hierarchy, which currently exists behind
a __DEVEL__ mount option. The core support is mostly complete but
individual controllers need further work. To explain the design and
rationales of the the unified hierarchy
Documentation/cgroups/unified-hierarchy.txt
is added.
Another notable change is css (cgroup_subsys_state - what each
controller uses to identify and interact with a cgroup) iteration
update. This is part of continuing updates on css object lifetime and
visibility. cgroup started with reference count draining on removal
way back and is now reaching a point where csses behave and are
iterated like normal refcnted objects albeit with some complexities to
allow distinguishing the state where they're being deleted. The css
iteration update isn't taken advantage of yet but is planned to be
used to simplify memcg significantly"
* 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (77 commits)
cgroup: disallow disabled controllers on the default hierarchy
cgroup: don't destroy the default root
cgroup: disallow debug controller on the default hierarchy
cgroup: clean up MAINTAINERS entries
cgroup: implement css_tryget()
device_cgroup: use css_has_online_children() instead of has_children()
cgroup: convert cgroup_has_live_children() into css_has_online_children()
cgroup: use CSS_ONLINE instead of CGRP_DEAD
cgroup: iterate cgroup_subsys_states directly
cgroup: introduce CSS_RELEASED and reduce css iteration fallback window
cgroup: move cgroup->serial_nr into cgroup_subsys_state
cgroup: link all cgroup_subsys_states in their sibling lists
cgroup: move cgroup->sibling and ->children into cgroup_subsys_state
cgroup: remove cgroup->parent
device_cgroup: remove direct access to cgroup->children
memcg: update memcg_has_children() to use css_next_child()
memcg: remove tasks/children test from mem_cgroup_force_empty()
cgroup: remove css_parent()
cgroup: skip refcnting on normal root csses and cgrp_dfl_root self css
cgroup: use cgroup->self.refcnt for cgroup refcnting
...
Convert all cftype->write_string() users to the new cftype->write()
which maps directly to kernfs write operation and has full access to
kernfs and cgroup contexts. The conversions are mostly mechanical.
* @css and @cft are accessed using of_css() and of_cft() accessors
respectively instead of being specified as arguments.
* Should return @nbytes on success instead of 0.
* @buf is not trimmed automatically. Trim if necessary. Note that
blkcg and netprio don't need this as the parsers already handle
whitespaces.
cftype->write_string() has no user left after the conversions and
removed.
While at it, remove unnecessary local variable @p in
cgroup_subtree_control_write() and stale comment about
CGROUP_LOCAL_BUFFER_SIZE in cgroup_freezer.c.
This patch doesn't introduce any visible behavior changes.
v2: netprio was missing from conversion. Converted.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: "David S. Miller" <davem@davemloft.net>
Pull cgroup updates from Tejun Heo:
"A lot updates for cgroup:
- The biggest one is cgroup's conversion to kernfs. cgroup took
after the long abandoned vfs-entangled sysfs implementation and
made it even more convoluted over time. cgroup's internal objects
were fused with vfs objects which also brought in vfs locking and
object lifetime rules. Naturally, there are places where vfs rules
don't fit and nasty hacks, such as credential switching or lock
dance interleaving inode mutex and cgroup_mutex with object serial
number comparison thrown in to decide whether the operation is
actually necessary, needed to be employed.
After conversion to kernfs, internal object lifetime and locking
rules are mostly isolated from vfs interactions allowing shedding
of several nasty hacks and overall simplification. This will also
allow implmentation of operations which may affect multiple cgroups
which weren't possible before as it would have required nesting
i_mutexes.
- Various simplifications including dropping of module support,
easier cgroup name/path handling, simplified cgroup file type
handling and task_cg_lists optimization.
- Prepatory changes for the planned unified hierarchy, which is still
a patchset away from being actually operational. The dummy
hierarchy is updated to serve as the default unified hierarchy.
Controllers which aren't claimed by other hierarchies are
associated with it, which BTW was what the dummy hierarchy was for
anyway.
- Various fixes from Li and others. This pull request includes some
patches to add missing slab.h to various subsystems. This was
triggered xattr.h include removal from cgroup.h. cgroup.h
indirectly got included a lot of files which brought in xattr.h
which brought in slab.h.
There are several merge commits - one to pull in kernfs updates
necessary for converting cgroup (already in upstream through
driver-core), others for interfering changes in the fixes branch"
* 'for-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (74 commits)
cgroup: remove useless argument from cgroup_exit()
cgroup: fix spurious lockdep warning in cgroup_exit()
cgroup: Use RCU_INIT_POINTER(x, NULL) in cgroup.c
cgroup: break kernfs active_ref protection in cgroup directory operations
cgroup: fix cgroup_taskset walking order
cgroup: implement CFTYPE_ONLY_ON_DFL
cgroup: make cgrp_dfl_root mountable
cgroup: drop const from @buffer of cftype->write_string()
cgroup: rename cgroup_dummy_root and related names
cgroup: move ->subsys_mask from cgroupfs_root to cgroup
cgroup: treat cgroup_dummy_root as an equivalent hierarchy during rebinding
cgroup: remove NULL checks from [pr_cont_]cgroup_{name|path}()
cgroup: use cgroup_setup_root() to initialize cgroup_dummy_root
cgroup: reorganize cgroup bootstrapping
cgroup: relocate setting of CGRP_DEAD
cpuset: use rcu_read_lock() to protect task_cs()
cgroup_freezer: document freezer_fork() subtleties
cgroup: update cgroup_transfer_tasks() to either succeed or fail
cgroup: drop task_lock() protection around task->cgroups
cgroup: update how a newly forked task gets associated with css_set
...
cftype->write_string() just passes on the writeable buffer from kernfs
and there's no reason to add const restriction on the buffer. The
only thing const achieves is unnecessarily complicating parsing of the
buffer. Drop const from @buffer.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Block layer currently abuses rq->csd.list.next for storing fifo_time.
That is a terrible hack and completely unnecessary as well. Union
achieves the same space saving in a cleaner way.
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
cftype->max_write_len is used to extend the maximum size of writes.
It's interpreted in such a way that the actual maximum size is one
less than the specified value. The default size is defined by
CGROUP_LOCAL_BUFFER_SIZE. Its interpretation is quite confusing - its
value is decremented by 1 and then compared for equality with max
size, which means that the actual default size is
CGROUP_LOCAL_BUFFER_SIZE - 2, which is 62 chars.
There's no point in having a limit that low. Update its definition so
that it means the actual string length sans termination and anything
below PAGE_SIZE-1 is treated as PAGE_SIZE-1.
.max_write_len for "release_agent" is updated to PATH_MAX-1 and
cgroup_release_agent_write() is updated so that the redundant strlen()
check is removed and it uses strlcpy() instead of strcpy().
.max_write_len initializations in blk-throttle.c and cfq-iosched.c are
no longer necessary and removed. The one in cpuset is kept unchanged
as it's an approximated value to begin with.
This will also make transition to kernfs smoother.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. This patch
replaces cftype->read_seq_string() with cftype->seq_show() which is
not limited to single_open() operation and will map directcly to
kernfs seq_file interface.
The conversions are mechanical. As ->seq_show() doesn't have @css and
@cft, the functions which make use of them are converted to use
seq_css() and seq_cft() respectively. In several occassions, e.f. if
it has seq_string in its name, the function name is updated to fit the
new method better.
This patch does not introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Now that seqcounts are lockdep enabled objects, we need to explicitly
initialize runtime allocated seqcounts so that lockdep can track them.
Without this patch, Fengguang was seeing:
[ 4.127282] INFO: trying to register non-static key.
[ 4.128027] the code is fine but needs lockdep annotation.
[ 4.128027] turning off the locking correctness validator.
[ 4.128027] CPU: 0 PID: 96 Comm: kworker/u4:1 Not tainted 3.12.0-next-20131108-10601-gbad570d #2
[ 4.128027] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ ... ]
[ 4.128027] Call Trace:
[ 4.128027] [<7908e744>] ? console_unlock+0x353/0x380
[ 4.128027] [<79dc7cf2>] dump_stack+0x48/0x60
[ 4.128027] [<7908953e>] __lock_acquire.isra.26+0x7e3/0xceb
[ 4.128027] [<7908a1c5>] lock_acquire+0x71/0x9a
[ 4.128027] [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
[ 4.128027] [<7940658b>] throtl_update_dispatch_stats+0x7c/0x153
[ 4.128027] [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
[ 4.128027] [<794079aa>] blk_throtl_bio+0x1c3/0x485
...
Use u64_stats_init() for all affected data structures, which initializes
the seqcount.
Reported-and-Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
[ Folded in another fix from the mailing list as well as a fix to that fix. Tweaked commit message. ]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1384314134-6895-1-git-send-email-john.stultz@linaro.org
[ So I actually think that the two SOBs from PeterZ are the right depiction of the patch route. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull block IO fixes from Jens Axboe:
"After merge window, no new stuff this time only a collection of neatly
confined and simple fixes"
* 'for-3.12/core' of git://git.kernel.dk/linux-block:
cfq: explicitly use 64bit divide operation for 64bit arguments
block: Add nr_bios to block_rq_remap tracepoint
If the queue is dying then we only call the rq->end_io callout. This leaves bios setup on the request, because the caller assumes when the blk_execute_rq_nowait/blk_execute_rq call has completed that the rq->bios have been cleaned up.
bio-integrity: Fix use of bs->bio_integrity_pool after free
blkcg: relocate root_blkg setting and clearing
block: Convert kmalloc_node(...GFP_ZERO...) to kzalloc_node(...)
block: trace all devices plug operation
'samples' is 64bit operant, but do_div() second parameter is 32.
do_div silently truncates high 32 bits and calculated result
is invalid.
In case if low 32bit of 'samples' are zeros then do_div() produces
kernel crash.
Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
cgroup is currently in the process of transitioning to using struct
cgroup_subsys_state * as the primary handle instead of struct cgroup.
Please see the previous commit which converts the subsystem methods
for rationale.
This patch converts all cftype file operations to take @css instead of
@cgroup. cftypes for the cgroup core files don't have their subsytem
pointer set. These will automatically use the dummy_css added by the
previous patch and can be converted the same way.
Most subsystem conversions are straight forwards but there are some
interesting ones.
* freezer: update_if_frozen() is also converted to take @css instead
of @cgroup for consistency. This will make the code look simpler
too once iterators are converted to use css.
* memory/vmpressure: mem_cgroup_from_css() needs to be exported to
vmpressure while mem_cgroup_from_cont() can be made static.
Updated accordingly.
* cpu: cgroup_tg() doesn't have any user left. Removed.
* cpuacct: cgroup_ca() doesn't have any user left. Removed.
* hugetlb: hugetlb_cgroup_form_cgroup() doesn't have any user left.
Removed.
* net_cls: cgrp_cls_state() doesn't have any user left. Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Steven Rostedt <rostedt@goodmis.org>
There's a race between elevator switching and normal io operation.
Because the allocation of struct elevator_queue and struct elevator_data
don't in a atomic operation.So there are have chance to use NULL
->elevator_data.
For example:
Thread A: Thread B
blk_queu_bio elevator_switch
spin_lock_irq(q->queue_block) elevator_alloc
elv_merge elevator_init_fn
Because call elevator_alloc, it can't hold queue_lock and the
->elevator_data is NULL.So at the same time, threadA call elv_merge and
nedd some info of elevator_data.So the crash happened.
Move the elevator_alloc into func elevator_init_fn, it make the
operations in a atomic operation.
Using the follow method can easy reproduce this bug
1:dd if=/dev/sdb of=/dev/null
2:while true;do echo noop > scheduler;echo deadline > scheduler;done
The test method also use this method.
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Just a little convenience macro - main reason to add it now is preparing
for immutable bio vecs, it'll reduce the size of the patch that puts
bi_sector/bi_size/bi_idx into a struct bvec_iter.
Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
CC: Lars Ellenberg <drbd-dev@lists.linbit.com>
CC: Jiri Kosina <jkosina@suse.cz>
CC: Alasdair Kergon <agk@redhat.com>
CC: dm-devel@redhat.com
CC: Neil Brown <neilb@suse.de>
CC: Martin Schwidefsky <schwidefsky@de.ibm.com>
CC: Heiko Carstens <heiko.carstens@de.ibm.com>
CC: linux-s390@vger.kernel.org
CC: Chris Mason <chris.mason@fusionio.com>
CC: Steven Whitehouse <swhiteho@redhat.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Pull block IO core bits from Jens Axboe:
"Below are the core block IO bits for 3.9. It was delayed a few days
since my workstation kept crashing every 2-8h after pulling it into
current -git, but turns out it is a bug in the new pstate code (divide
by zero, will report separately). In any case, it contains:
- The big cfq/blkcg update from Tejun and and Vivek.
- Additional block and writeback tracepoints from Tejun.
- Improvement of the should sort (based on queues) logic in the plug
flushing.
- _io() variants of the wait_for_completion() interface, using
io_schedule() instead of schedule() to contribute to io wait
properly.
- Various little fixes.
You'll get two trivial merge conflicts, which should be easy enough to
fix up"
Fix up the trivial conflicts due to hlist traversal cleanups (commit
b67bfe0d42ca: "hlist: drop the node parameter from iterators").
* 'for-3.9/core' of git://git.kernel.dk/linux-block: (39 commits)
block: remove redundant check to bd_openers()
block: use i_size_write() in bd_set_size()
cfq: fix lock imbalance with failed allocations
drivers/block/swim3.c: fix null pointer dereference
block: don't select PERCPU_RWSEM
block: account iowait time when waiting for completion of IO request
sched: add wait_for_completion_io[_timeout]
writeback: add more tracepoints
block: add block_{touch|dirty}_buffer tracepoint
buffer: make touch_buffer() an exported function
block: add @req to bio_{front|back}_merge tracepoints
block: add missing block_bio_complete() tracepoint
block: Remove should_sort judgement when flush blk_plug
block,elevator: use new hashtable implementation
cfq-iosched: add hierarchical cfq_group statistics
cfq-iosched: collect stats from dead cfqgs
cfq-iosched: separate out cfqg_stats_reset() from cfq_pd_reset_stats()
blkcg: make blkcg_print_blkgs() grab q locks instead of blkcg lock
block: RCU free request_queue
blkcg: implement blkg_[rw]stat_recursive_sum() and blkg_[rw]stat_merge()
...
I'm not sure why, but the hlist for each entry iterators were conceived
list_for_each_entry(pos, head, member)
The hlist ones were greedy and wanted an extra parameter:
hlist_for_each_entry(tpos, pos, head, member)
Why did they need an extra pos parameter? I'm not quite sure. Not only
they don't really need it, it also prevents the iterator from looking
exactly like the list iterator, which is unfortunate.
Besides the semantic patch, there was some manual work required:
- Fix up the actual hlist iterators in linux/list.h
- Fix up the declaration of other iterators based on the hlist ones.
- A very small amount of places were using the 'node' parameter, this
was modified to use 'obj->member' instead.
- Coccinelle didn't handle the hlist_for_each_entry_safe iterator
properly, so those had to be fixed up manually.
The semantic patch which is mostly the work of Peter Senna Tschudin is here:
@@
iterator name hlist_for_each_entry, hlist_for_each_entry_continue, hlist_for_each_entry_from, hlist_for_each_entry_rcu, hlist_for_each_entry_rcu_bh, hlist_for_each_entry_continue_rcu_bh, for_each_busy_worker, ax25_uid_for_each, ax25_for_each, inet_bind_bucket_for_each, sctp_for_each_hentry, sk_for_each, sk_for_each_rcu, sk_for_each_from, sk_for_each_safe, sk_for_each_bound, hlist_for_each_entry_safe, hlist_for_each_entry_continue_rcu, nr_neigh_for_each, nr_neigh_for_each_safe, nr_node_for_each, nr_node_for_each_safe, for_each_gfn_indirect_valid_sp, for_each_gfn_sp, for_each_host;
type T;
expression a,c,d,e;
identifier b;
statement S;
@@
-T b;
<+... when != b
(
hlist_for_each_entry(a,
- b,
c, d) S
|
hlist_for_each_entry_continue(a,
- b,
c) S
|
hlist_for_each_entry_from(a,
- b,
c) S
|
hlist_for_each_entry_rcu(a,
- b,
c, d) S
|
hlist_for_each_entry_rcu_bh(a,
- b,
c, d) S
|
hlist_for_each_entry_continue_rcu_bh(a,
- b,
c) S
|
for_each_busy_worker(a, c,
- b,
d) S
|
ax25_uid_for_each(a,
- b,
c) S
|
ax25_for_each(a,
- b,
c) S
|
inet_bind_bucket_for_each(a,
- b,
c) S
|
sctp_for_each_hentry(a,
- b,
c) S
|
sk_for_each(a,
- b,
c) S
|
sk_for_each_rcu(a,
- b,
c) S
|
sk_for_each_from
-(a, b)
+(a)
S
+ sk_for_each_from(a) S
|
sk_for_each_safe(a,
- b,
c, d) S
|
sk_for_each_bound(a,
- b,
c) S
|
hlist_for_each_entry_safe(a,
- b,
c, d, e) S
|
hlist_for_each_entry_continue_rcu(a,
- b,
c) S
|
nr_neigh_for_each(a,
- b,
c) S
|
nr_neigh_for_each_safe(a,
- b,
c, d) S
|
nr_node_for_each(a,
- b,
c) S
|
nr_node_for_each_safe(a,
- b,
c, d) S
|
- for_each_gfn_sp(a, c, d, b) S
+ for_each_gfn_sp(a, c, d) S
|
- for_each_gfn_indirect_valid_sp(a, c, d, b) S
+ for_each_gfn_indirect_valid_sp(a, c, d) S
|
for_each_host(a,
- b,
c) S
|
for_each_host_safe(a,
- b,
c, d) S
|
for_each_mesh_entry(a,
- b,
c, d) S
)
...+>
[akpm@linux-foundation.org: drop bogus change from net/ipv4/raw.c]
[akpm@linux-foundation.org: drop bogus hunk from net/ipv6/raw.c]
[akpm@linux-foundation.org: checkpatch fixes]
[akpm@linux-foundation.org: fix warnings]
[akpm@linux-foudnation.org: redo intrusive kvm changes]
Tested-by: Peter Senna Tschudin <peter.senna@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
While stress-running very-small container scenarios with the Kernel Memory
Controller, I've run into a lockdep-detected lock imbalance in
cfq-iosched.c.
I'll apologize beforehand for not posting a backlog: I didn't anticipate
it would be so hard to reproduce, so I didn't save my serial output and
went directly on debugging. Turns out that it did not happen again in
more than 20 runs, making it a quite rare pattern.
But here is my analysis:
When we are in very low-memory situations, we will arrive at
cfq_find_alloc_queue and may not find a queue, having to resort to the oom
queue, in an rcu-locked condition:
if (!cfqq || cfqq == &cfqd->oom_cfqq)
[ ... ]
Next, we will release the rcu lock, and try to allocate a queue, retrying
if we succeed:
rcu_read_unlock();
spin_unlock_irq(cfqd->queue->queue_lock);
new_cfqq = kmem_cache_alloc_node(cfq_pool,
gfp_mask | __GFP_ZERO,
cfqd->queue->node);
spin_lock_irq(cfqd->queue->queue_lock);
if (new_cfqq)
goto retry;
We are unlocked at this point, but it should be fine, since we will
reacquire the rcu_read_lock when we retry.
Except of course, that we may not retry: the allocation may very well fail
and we'll keep on going through the flow:
The next branch is:
if (cfqq) {
[ ... ]
} else
cfqq = &cfqd->oom_cfqq;
And right before exiting, we'll issue rcu_read_unlock().
Being already unlocked, this is the likely source of our imbalance. Since
cfqq is either already NULL or made NULL in the first statement of the
outter branch, the only viable alternative here seems to be to return the
oom queue right away in case of allocation failure.
Please review the following patch and apply if you agree with my analysis.
Signed-off-by: Glauber Costa <glommer@parallels.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Unfortunately, at this point, there's no way to make the existing
statistics hierarchical without creating nasty surprises for the
existing users. Just create recursive counterpart of the existing
stats.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
To support hierarchical stats, it's necessary to remember stats from
dead children. Add cfqg->dead_stats and make a dying cfqg transfer
its stats to the parent's dead-stats.
The transfer happens form ->pd_offline_fn() and it is possible that
there are some residual IOs completing afterwards. Currently, we lose
these stats. Given that cgroup removal isn't a very high frequency
operation and the amount of residual IOs on offline are likely to be
nil or small, this shouldn't be a big deal and the complexity needed
to handle residual IOs - another callback and rather elaborate
synchronization to reach and lock the matching q - doesn't seem
justified.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Separate out cfqg_stats_reset() which takes struct cfqg_stats * from
cfq_pd_reset_stats() and move the latter to where other pd methods are
defined. cfqg_stats_reset() will be used to implement hierarchical
stats.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Rename blkg_rwstat_sum() to blkg_rwstat_total(). sum will be used for
summing up stats from multiple blkgs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Tejun Heo
Linus Torvalds
Jens Axboe
Arianna Avanzini
Tahsin Erdogan
Konstantin Khlebnikov
Jeff Moyer
Toshiaki Makita
Masanari Iida
Jan Kara
Peter Zijlstra
Anatol Pomozov
Joe Perches
Jianpeng Ma
Kent Overstreet
Sasha Levin
Glauber Costa