[ Upstream commit 2de791ab4918969d8108f15238a701968375f235 ]
Changes from v1:
- update commit description with proper ref-accounting justification
commit db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree")
introduce leak forbfq_group and blkcg_gq objects because of get/put
imbalance.
In fact whole idea of original commit is wrong because bfq_group entity
can not dissapear under us because it is referenced by child bfq_queue's
entities from here:
-> bfq_init_entity()
->bfqg_and_blkg_get(bfqg);
->entity->parent = bfqg->my_entity
-> bfq_put_queue(bfqq)
FINAL_PUT
->bfqg_and_blkg_put(bfqq_group(bfqq))
->kmem_cache_free(bfq_pool, bfqq);
So parent entity can not disappear while child entity is in tree,
and child entities already has proper protection.
This patch revert commit db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree")
bfq_group leak trace caused by bad commit:
-> blkg_alloc
-> bfq_pq_alloc
-> bfqg_get (+1)
->bfq_activate_bfqq
->bfq_activate_requeue_entity
-> __bfq_activate_entity
->bfq_get_entity
->bfqg_and_blkg_get (+1) <==== : Note1
->bfq_del_bfqq_busy
->bfq_deactivate_entity+0x53/0xc0 [bfq]
->__bfq_deactivate_entity+0x1b8/0x210 [bfq]
-> bfq_forget_entity(is_in_service = true)
entity->on_st_or_in_serv = false <=== :Note2
if (is_in_service)
return; ==> do not touch reference
-> blkcg_css_offline
-> blkcg_destroy_blkgs
-> blkg_destroy
-> bfq_pd_offline
-> __bfq_deactivate_entity
if (!entity->on_st_or_in_serv) /* true, because (Note2)
return false;
-> bfq_pd_free
-> bfqg_put() (-1, byt bfqg->ref == 2) because of (Note2)
So bfq_group and blkcg_gq will leak forever, see test-case below.
##TESTCASE_BEGIN:
#!/bin/bash
max_iters=${1:-100}
#prep cgroup mounts
mount -t tmpfs cgroup_root /sys/fs/cgroup
mkdir /sys/fs/cgroup/blkio
mount -t cgroup -o blkio none /sys/fs/cgroup/blkio
# Prepare blkdev
grep blkio /proc/cgroups
truncate -s 1M img
losetup /dev/loop0 img
echo bfq > /sys/block/loop0/queue/scheduler
grep blkio /proc/cgroups
for ((i=0;i<max_iters;i++))
do
mkdir -p /sys/fs/cgroup/blkio/a
echo 0 > /sys/fs/cgroup/blkio/a/cgroup.procs
dd if=/dev/loop0 bs=4k count=1 of=/dev/null iflag=direct 2> /dev/null
echo 0 > /sys/fs/cgroup/blkio/cgroup.procs
rmdir /sys/fs/cgroup/blkio/a
grep blkio /proc/cgroups
done
##TESTCASE_END:
Fixes: db37a34c563b ("block, bfq: get a ref to a group when adding it to a service tree")
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 4d38a87fbb77fb9ff2ff4e914162a8ae6453eff5 upstream.
In bfq_pd_offline(), the function bfq_flush_idle_tree() is invoked to
flush the rb tree that contains all idle entities belonging to the pd
(cgroup) being destroyed. In particular, bfq_flush_idle_tree() is
invoked before bfq_reparent_active_queues(). Yet the latter may happen
to add some entities to the idle tree. It happens if, in some of the
calls to bfq_bfqq_move() performed by bfq_reparent_active_queues(),
the queue to move is empty and gets expired.
This commit simply reverses the invocation order between
bfq_flush_idle_tree() and bfq_reparent_active_queues().
Tested-by: cki-project@redhat.com
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 576682fa52cbd95deb3773449566274f206acc58 upstream.
bfq_reparent_leaf_entity() reparents the input leaf entity (a leaf
entity represents just a bfq_queue in an entity tree). Yet, the input
entity is guaranteed to always be a leaf entity only in two-level
entity trees. In this respect, because of the error fixed by
commit 14afc5936197 ("block, bfq: fix overwrite of bfq_group pointer
in bfq_find_set_group()"), all (wrongly collapsed) entity trees happened
to actually have only two levels. After the latter commit, this does not
hold any longer.
This commit fixes this problem by modifying
bfq_reparent_leaf_entity(), so that it searches an active leaf entity
down the path that stems from the input entity. Such a leaf entity is
guaranteed to exist when bfq_reparent_leaf_entity() is invoked.
Tested-by: cki-project@redhat.com
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit c8997736650060594845e42c5d01d3118aec8d25 upstream.
A bfq_put_queue() may be invoked in __bfq_bic_change_cgroup(). The
goal of this put is to release a process reference to a bfq_queue. But
process-reference releases may trigger also some extra operation, and,
to this goal, are handled through bfq_release_process_ref(). So, turn
the invocation of bfq_put_queue() into an invocation of
bfq_release_process_ref().
Tested-by: cki-project@redhat.com
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit fd1bb3ae54a9a2e0c42709de861c69aa146b8955 ]
Commit ecedd3d7e199 ("block, bfq: get extra ref to prevent a queue
from being freed during a group move") gets an extra reference to a
bfq_queue before possibly deactivating it (temporarily), in
bfq_bfqq_move(). This prevents the bfq_queue from disappearing before
being reactivated in its new group.
Yet, the bfq_queue may also be expired (i.e., its service may be
stopped) before the bfq_queue is deactivated. And also an expiration
may lead to a premature freeing. This commit fixes this issue by
simply moving forward the getting of the extra reference already
introduced by commit ecedd3d7e199 ("block, bfq: get extra ref to
prevent a queue from being freed during a group move").
Reported-by: cki-project@redhat.com
Tested-by: cki-project@redhat.com
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Dmitry Monakhov