linux-stable.git/include/linux/blk-cgroup.h, branch v5.13.2

block: simplify bdev/disk lookup in blkdev_get

2020-12-01T21:53:39+00:00

To simplify block device lookup and a few other upcoming areas, make sure
that we always have a struct block_device available for each disk and
each partition, and only find existing block devices in bdget.  The only
downside of this is that each device and partition uses a little more
memory.  The upside will be that a lot of code can be simplified.

With that all we need to look up the block device is to lookup the inode
and do a few sanity checks on the gendisk, instead of the separate lookup
for the gendisk.  For blk-cgroup which wants to access a gendisk without
opening it, a new blkdev_{get,put}_no_open low-level interface is added
to replace the previous get_gendisk use.

Note that the change to look up block device directly instead of the two
step lookup using struct gendisk causes a subtile change in behavior:
accessing a non-existing partition on an existing block device can now
cause a call to request_module.  That call is harmless, and in practice
no recent system will access these nodes as they aren't created by udev
and static /dev/ setups are unusual.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Reviewed-by: Hannes Reinecke 
Signed-off-by: Jens Axboe

writeback: remove struct bdi_writeback_congested

2020-07-08T23:05:53+00:00

We never set any congested bits in the group writeback instances of it.
And for the simpler bdi-wide case a simple scalar field is all that
that is needed.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

blk-cgroup: remove blkcg_bio_issue_check

2020-06-29T15:09:08+00:00

blkcg_bio_issue_check is a giant inline function that does three entirely
different things.  Factor out the blk-cgroup related bio initalization
into a new helper, and the open code the sequence in the only caller,
relying on the fact that all the actual functionality is stubbed out for
non-cgroup builds.

Acked-by: Tejun Heo 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

blk-cgroup: move rcu locking from blkcg_bio_issue_check to blk_throtl_bio

2020-06-29T15:09:08+00:00

The only thing in blkcg_bio_issue_check that needs to be under
rcu_read_lock is blk_throtl_bio, so move the locking there.

Acked-by: Tejun Heo 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

blk-cgroup: remove the !bio->bi_blkg check in blkcg_bio_issue_check

2020-06-29T15:09:08+00:00

This is purely a sanity check for grave programming errors.  Remove it
to simplify further work in this area.

Acked-by: Tejun Heo 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

block: move the bio cgroup associatation helpers to blk-cgroup.c

2020-06-29T15:09:08+00:00

Keep the cgroup code together.

Acked-by: Tejun Heo 
Reviewed-by: Johannes Thumshirn 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

blk-iocost: switch to fixed non-auto-decaying use_delay

2020-04-30T21:54:45+00:00

The use_delay mechanism was introduced by blk-iolatency to hold memory
allocators accountable for the reclaim and other shared IOs they cause. The
duration of the delay is dynamically balanced between iolatency increasing the
value on each target miss and it auto-decaying as time passes and threads get
delayed on it.

While this works well for iolatency, iocost's control model isn't compatible
with it. There is no repeated "violation" events which can be balanced against
auto-decaying. iocost instead knows how much a given cgroup is over budget and
wants to prevent that cgroup from issuing IOs while over budget. Until now,
iocost has been adding the cost of force-issued IOs. However, this doesn't
reflect the amount which is already over budget and is simply not enough to
counter the auto-decaying allowing anon-memory leaking low priority cgroup to
go over its alloted share of IOs.

As auto-decaying doesn't make much sense for iocost, this patch introduces a
different mode of operation for use_delay - when blkcg_set_delay() are used
insted of blkcg_add/use_delay(), the delay duration is not auto-decayed until it
is explicitly cleared with blkcg_clear_delay(). iocost is updated to keep the
delay duration synchronized to the budget overage amount.

With this change, iocost can effectively police cgroups which generate
significant amount of force-issued IOs.

Signed-off-by: Tejun Heo 
Cc: Josef Bacik 
Signed-off-by: Jens Axboe

block: replace BIO_QUEUE_ENTERED with BIO_CGROUP_ACCT

2020-04-29T15:33:26+00:00

BIO_QUEUE_ENTERED is only used for cgroup accounting now, so rename
the flag and move setting it into the cgroup code.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

blkcg: don't offline parent blkcg first

2020-04-01T20:56:44+00:00

blkcg->cgwb_refcnt is used to delay blkcg offlining so that blkgs
don't get offlined while there are active cgwbs on them.  However, it
ends up making offlining unordered sometimes causing parents to be
offlined before children.

Let's fix this by making child blkcgs pin the parents' online states.

Note that pin/unpin names are chosen over get/put intentionally
because css uses get/put online for something different.

Signed-off-by: Tejun Heo 
Signed-off-by: Jens Axboe

blkcg: rename blkcg->cgwb_refcnt to ->online_pin and always use it

2020-04-01T20:56:42+00:00

blkcg->cgwb_refcnt is used to delay blkcg offlining so that blkgs
don't get offlined while there are active cgwbs on them.  However, it
ends up making offlining unordered sometimes causing parents to be
offlined before children.

To fix it, we want child blkcgs to pin the parents' online states
turning the refcnt into a more generic online pinning mechanism.

In prepartion,

* blkcg->cgwb_refcnt -> blkcg->online_pin
* blkcg_cgwb_get/put() -> blkcg_pin/unpin_online()
* Take them out of CONFIG_CGROUP_WRITEBACK

Signed-off-by: Tejun Heo 
Signed-off-by: Jens Axboe