[PATCH v2 0/3] block, bfq: minor cleanup and fix

[PATCH v2 0/3] block, bfq: minor cleanup and fix

[Yu Kuai]

Chagnes in v2:
 - add comment in patch 2
 - remove patch 4, since the problem do not exist.

Yu Kuai (3):
  block, bfq: cleanup bfq_bfqq_to_bfqg()
  block, bfq: avoid moving bfqq to it's parent bfqg
  block, bfq: don't move oom_bfqq

 block/bfq-cgroup.c  | 16 +++++++++++++++-
 block/bfq-iosched.c |  4 ++--
 block/bfq-iosched.h |  1 -
 block/bfq-wf2q.c    | 15 ---------------
 4 files changed, 17 insertions(+), 19 deletions(-)

-- 
2.31.1

[PATCH v2 1/3] block, bfq: cleanup bfq_bfqq_to_bfqg()

[Yu Kuai]

Use bfq_group() instead, which do the same thing.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 block/bfq-iosched.c |  4 ++--
 block/bfq-iosched.h |  1 -
 block/bfq-wf2q.c    | 15 ---------------
 3 files changed, 2 insertions(+), 18 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 4f671e3d2f2d..e2c49131559f 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -774,7 +774,7 @@ bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
 	if (!bfqq->next_rq)
 		return;
 
-	bfqq->pos_root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree;
+	bfqq->pos_root = &bfqq_group(bfqq)->rq_pos_tree;
 	__bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root,
 			blk_rq_pos(bfqq->next_rq), &parent, &p);
 	if (!__bfqq) {
@@ -2669,7 +2669,7 @@ static struct bfq_queue *bfqq_find_close(struct bfq_data *bfqd,
 					 struct bfq_queue *bfqq,
 					 sector_t sector)
 {
-	struct rb_root *root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree;
+	struct rb_root *root = &bfqq_group(bfqq)->rq_pos_tree;
 	struct rb_node *parent, *node;
 	struct bfq_queue *__bfqq;
 
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index cc08940c87e3..6bb59ce86a86 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -1063,7 +1063,6 @@ extern struct blkcg_policy blkcg_policy_bfq;
 	for (parent = NULL; entity ; entity = parent)
 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
 
-struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq);
 struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
 unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd);
 struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity);
diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index 69d169d39578..7ade26ac9cba 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -142,16 +142,6 @@ static bool bfq_update_next_in_service(struct bfq_sched_data *sd,
 
 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 
-struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
-{
-	struct bfq_entity *group_entity = bfqq->entity.parent;
-
-	if (!group_entity)
-		group_entity = &bfqq->bfqd->root_group->entity;
-
-	return container_of(group_entity, struct bfq_group, entity);
-}
-
 /*
  * Returns true if this budget changes may let next_in_service->parent
  * become the next_in_service entity for its parent entity.
@@ -244,11 +234,6 @@ static void bfq_update_groups_with_pending_reqs(struct bfq_entity *entity)
 
 #else /* CONFIG_BFQ_GROUP_IOSCHED */
 
-struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
-{
-	return bfqq->bfqd->root_group;
-}
-
 static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)
 {
 	return false;
-- 
2.31.1

[PATCH v2 2/3] block, bfq: avoid moving bfqq to it's parent bfqg

[Yu Kuai]

Moving bfqq to it's parent bfqg is pointless.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 block/bfq-cgroup.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 09ff0bb1042c..5e65b0407e85 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -645,6 +645,14 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 		   struct bfq_group *bfqg)
 {
 	struct bfq_entity *entity = &bfqq->entity;
+	struct bfq_group *old_parent = bfq_group(bfqq);
+
+	/*
+	 * No point to move bfqq to the same group, which can happen when
+	 * root group is offlined
+	 */
+	if (old_parent == bfqg)
+		return;
 
 	/*
 	 * Get extra reference to prevent bfqq from being freed in
@@ -666,7 +674,7 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 		bfq_deactivate_bfqq(bfqd, bfqq, false, false);
 	else if (entity->on_st_or_in_serv)
 		bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
-	bfqg_and_blkg_put(bfqq_group(bfqq));
+	bfqg_and_blkg_put(old_parent);
 
 	if (entity->parent &&
 	    entity->parent->last_bfqq_created == bfqq)
-- 
2.31.1

[PATCH v2 3/3] block, bfq: don't move oom_bfqq

[Yu Kuai]

Our test report a UAF:

[ 2073.019181] ==================================================================
[ 2073.019188] BUG: KASAN: use-after-free in __bfq_put_async_bfqq+0xa0/0x168
[ 2073.019191] Write of size 8 at addr ffff8000ccf64128 by task rmmod/72584
[ 2073.019192]
[ 2073.019196] CPU: 0 PID: 72584 Comm: rmmod Kdump: loaded Not tainted 4.19.90-yk #5
[ 2073.019198] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
[ 2073.019200] Call trace:
[ 2073.019203]  dump_backtrace+0x0/0x310
[ 2073.019206]  show_stack+0x28/0x38
[ 2073.019210]  dump_stack+0xec/0x15c
[ 2073.019216]  print_address_description+0x68/0x2d0
[ 2073.019220]  kasan_report+0x238/0x2f0
[ 2073.019224]  __asan_store8+0x88/0xb0
[ 2073.019229]  __bfq_put_async_bfqq+0xa0/0x168
[ 2073.019233]  bfq_put_async_queues+0xbc/0x208
[ 2073.019236]  bfq_pd_offline+0x178/0x238
[ 2073.019240]  blkcg_deactivate_policy+0x1f0/0x420
[ 2073.019244]  bfq_exit_queue+0x128/0x178
[ 2073.019249]  blk_mq_exit_sched+0x12c/0x160
[ 2073.019252]  elevator_exit+0xc8/0xd0
[ 2073.019256]  blk_exit_queue+0x50/0x88
[ 2073.019259]  blk_cleanup_queue+0x228/0x3d8
[ 2073.019267]  null_del_dev+0xfc/0x1e0 [null_blk]
[ 2073.019274]  null_exit+0x90/0x114 [null_blk]
[ 2073.019278]  __arm64_sys_delete_module+0x358/0x5a0
[ 2073.019282]  el0_svc_common+0xc8/0x320
[ 2073.019287]  el0_svc_handler+0xf8/0x160
[ 2073.019290]  el0_svc+0x10/0x218
[ 2073.019291]
[ 2073.019294] Allocated by task 14163:
[ 2073.019301]  kasan_kmalloc+0xe0/0x190
[ 2073.019305]  kmem_cache_alloc_node_trace+0x1cc/0x418
[ 2073.019308]  bfq_pd_alloc+0x54/0x118
[ 2073.019313]  blkcg_activate_policy+0x250/0x460
[ 2073.019317]  bfq_create_group_hierarchy+0x38/0x110
[ 2073.019321]  bfq_init_queue+0x6d0/0x948
[ 2073.019325]  blk_mq_init_sched+0x1d8/0x390
[ 2073.019330]  elevator_switch_mq+0x88/0x170
[ 2073.019334]  elevator_switch+0x140/0x270
[ 2073.019338]  elv_iosched_store+0x1a4/0x2a0
[ 2073.019342]  queue_attr_store+0x90/0xe0
[ 2073.019348]  sysfs_kf_write+0xa8/0xe8
[ 2073.019351]  kernfs_fop_write+0x1f8/0x378
[ 2073.019359]  __vfs_write+0xe0/0x360
[ 2073.019363]  vfs_write+0xf0/0x270
[ 2073.019367]  ksys_write+0xdc/0x1b8
[ 2073.019371]  __arm64_sys_write+0x50/0x60
[ 2073.019375]  el0_svc_common+0xc8/0x320
[ 2073.019380]  el0_svc_handler+0xf8/0x160
[ 2073.019383]  el0_svc+0x10/0x218
[ 2073.019385]
[ 2073.019387] Freed by task 72584:
[ 2073.019391]  __kasan_slab_free+0x120/0x228
[ 2073.019394]  kasan_slab_free+0x10/0x18
[ 2073.019397]  kfree+0x94/0x368
[ 2073.019400]  bfqg_put+0x64/0xb0
[ 2073.019404]  bfqg_and_blkg_put+0x90/0xb0
[ 2073.019408]  bfq_put_queue+0x220/0x228
[ 2073.019413]  __bfq_put_async_bfqq+0x98/0x168
[ 2073.019416]  bfq_put_async_queues+0xbc/0x208
[ 2073.019420]  bfq_pd_offline+0x178/0x238
[ 2073.019424]  blkcg_deactivate_policy+0x1f0/0x420
[ 2073.019429]  bfq_exit_queue+0x128/0x178
[ 2073.019433]  blk_mq_exit_sched+0x12c/0x160
[ 2073.019437]  elevator_exit+0xc8/0xd0
[ 2073.019440]  blk_exit_queue+0x50/0x88
[ 2073.019443]  blk_cleanup_queue+0x228/0x3d8
[ 2073.019451]  null_del_dev+0xfc/0x1e0 [null_blk]
[ 2073.019459]  null_exit+0x90/0x114 [null_blk]
[ 2073.019462]  __arm64_sys_delete_module+0x358/0x5a0
[ 2073.019467]  el0_svc_common+0xc8/0x320
[ 2073.019471]  el0_svc_handler+0xf8/0x160
[ 2073.019474]  el0_svc+0x10/0x218
[ 2073.019475]
[ 2073.019479] The buggy address belongs to the object at ffff8000ccf63f00
 which belongs to the cache kmalloc-1024 of size 1024
[ 2073.019484] The buggy address is located 552 bytes inside of
 1024-byte region [ffff8000ccf63f00, ffff8000ccf64300)
[ 2073.019486] The buggy address belongs to the page:
[ 2073.019492] page:ffff7e000333d800 count:1 mapcount:0 mapping:ffff8000c0003a00 index:0x0 compound_mapcount: 0
[ 2073.020123] flags: 0x7ffff0000008100(slab|head)
[ 2073.020403] raw: 07ffff0000008100 ffff7e0003334c08 ffff7e00001f5a08 ffff8000c0003a00
[ 2073.020409] raw: 0000000000000000 00000000001c001c 00000001ffffffff 0000000000000000
[ 2073.020411] page dumped because: kasan: bad access detected
[ 2073.020412]
[ 2073.020414] Memory state around the buggy address:
[ 2073.020420]  ffff8000ccf64000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 2073.020424]  ffff8000ccf64080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 2073.020428] >ffff8000ccf64100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 2073.020430]                                   ^
[ 2073.020434]  ffff8000ccf64180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 2073.020438]  ffff8000ccf64200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 2073.020439] ==================================================================

The same problem exist in mainline as well.

This is because oom_bfqq is moved to a non-root group, thus root_group
is freed earlier.

Thus fix the problem by don't move oom_bfqq.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 block/bfq-cgroup.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 5e65b0407e85..22dd5b7229ae 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -654,6 +654,12 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 	if (old_parent == bfqg)
 		return;
 
+	/*
+	 * oom_bfqq is not allowed to move, oom_bfqq will hold ref to root_group
+	 * until elevator exit.
+	 */
+	if (bfqq == &bfqd->oom_bfqq)
+		return;
 	/*
 	 * Get extra reference to prevent bfqq from being freed in
 	 * next possible expire or deactivate.
-- 
2.31.1

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[yukuai (C)]

在 2021/12/31 11:23, Yu Kuai 写道:
> Chagnes in v2:
>   - add comment in patch 2
>   - remove patch 4, since the problem do not exist.
> 
friendly ping ...
> Yu Kuai (3):
>    block, bfq: cleanup bfq_bfqq_to_bfqg()
>    block, bfq: avoid moving bfqq to it's parent bfqg
>    block, bfq: don't move oom_bfqq
> 
>   block/bfq-cgroup.c  | 16 +++++++++++++++-
>   block/bfq-iosched.c |  4 ++--
>   block/bfq-iosched.h |  1 -
>   block/bfq-wf2q.c    | 15 ---------------
>   4 files changed, 17 insertions(+), 19 deletions(-)
> 

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[yukuai (C)]

在 2022/01/11 9:40, yukuai (C) 写道:
> 在 2021/12/31 11:23, Yu Kuai 写道:
>> Chagnes in v2:
>>   - add comment in patch 2
>>   - remove patch 4, since the problem do not exist.
>>
> friendly ping ...

Hi, Jens

Can this patchset be applied?

Thanks
>> Yu Kuai (3):
>>    block, bfq: cleanup bfq_bfqq_to_bfqg()
>>    block, bfq: avoid moving bfqq to it's parent bfqg
>>    block, bfq: don't move oom_bfqq
>>
>>   block/bfq-cgroup.c  | 16 +++++++++++++++-
>>   block/bfq-iosched.c |  4 ++--
>>   block/bfq-iosched.h |  1 -
>>   block/bfq-wf2q.c    | 15 ---------------
>>   4 files changed, 17 insertions(+), 19 deletions(-)
>>

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[Jan Kara]

On Fri 14-01-22 16:23:36, yukuai (C) wrote:
> 在 2022/01/11 9:40, yukuai (C) 写道:
> > 在 2021/12/31 11:23, Yu Kuai 写道:
> > > Chagnes in v2:
> > >   - add comment in patch 2
> > >   - remove patch 4, since the problem do not exist.
> > > 
> > friendly ping ...
> 
> Hi, Jens
> 
> Can this patchset be applied?

Maybe Jens is waiting for Paolo's ack as a BFQ maintainer. Paolo, what do
you think about the cleanups? They seem mostly obvious to me...

								Honza

> 
> Thanks
> > > Yu Kuai (3):
> > >    block, bfq: cleanup bfq_bfqq_to_bfqg()
> > >    block, bfq: avoid moving bfqq to it's parent bfqg
> > >    block, bfq: don't move oom_bfqq
> > > 
> > >   block/bfq-cgroup.c  | 16 +++++++++++++++-
> > >   block/bfq-iosched.c |  4 ++--
> > >   block/bfq-iosched.h |  1 -
> > >   block/bfq-wf2q.c    | 15 ---------------
> > >   4 files changed, 17 insertions(+), 19 deletions(-)
> > > 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[Paolo Valente]

> Il giorno 31 dic 2021, alle ore 04:23, Yu Kuai <yukuai3@huawei.com> ha scritto:
> 
> Chagnes in v2:
> - add comment in patch 2
> - remove patch 4, since the problem do not exist.
> 
> Yu Kuai (3):
>  block, bfq: cleanup bfq_bfqq_to_bfqg()
>  block, bfq: avoid moving bfqq to it's parent bfqg
>  block, bfq: don't move oom_bfqq
> 

All
Acked-by: Paolo Valente <paolo.valente@linaro.org>

Thanks,
Paolo


> block/bfq-cgroup.c  | 16 +++++++++++++++-
> block/bfq-iosched.c |  4 ++--
> block/bfq-iosched.h |  1 -
> block/bfq-wf2q.c    | 15 ---------------
> 4 files changed, 17 insertions(+), 19 deletions(-)
> 
> -- 
> 2.31.1
> 

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[yukuai (C)]

在 2021/12/31 11:23, Yu Kuai 写道:
> Chagnes in v2:
>   - add comment in patch 2
>   - remove patch 4, since the problem do not exist.
> 
> Yu Kuai (3):
>    block, bfq: cleanup bfq_bfqq_to_bfqg()
>    block, bfq: avoid moving bfqq to it's parent bfqg
>    block, bfq: don't move oom_bfqq
> 
>   block/bfq-cgroup.c  | 16 +++++++++++++++-
>   block/bfq-iosched.c |  4 ++--
>   block/bfq-iosched.h |  1 -
>   block/bfq-wf2q.c    | 15 ---------------
>   4 files changed, 17 insertions(+), 19 deletions(-)
> 
Hi, jens

Now that with acked-by Paolo, can you please applied this pathset?

Thanks,
Kuai

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[yukuai (C)]

在 2022/01/24 11:46, yukuai (C) 写道:
> 在 2021/12/31 11:23, Yu Kuai 写道:
>> Chagnes in v2:
>>   - add comment in patch 2
>>   - remove patch 4, since the problem do not exist.
>>
>> Yu Kuai (3):
>>    block, bfq: cleanup bfq_bfqq_to_bfqg()
>>    block, bfq: avoid moving bfqq to it's parent bfqg
>>    block, bfq: don't move oom_bfqq
>>
>>   block/bfq-cgroup.c  | 16 +++++++++++++++-
>>   block/bfq-iosched.c |  4 ++--
>>   block/bfq-iosched.h |  1 -
>>   block/bfq-wf2q.c    | 15 ---------------
>>   4 files changed, 17 insertions(+), 19 deletions(-)
>>
> Hi, jens
> 
> Now that with acked-by Paolo, can you please applied this pathset?
friendly ping ...
> 
> Thanks,
> Kuai

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[Jens Axboe]

On Fri, 31 Dec 2021 11:23:51 +0800, Yu Kuai wrote:
> Chagnes in v2:
>  - add comment in patch 2
>  - remove patch 4, since the problem do not exist.
> 
> Yu Kuai (3):
>   block, bfq: cleanup bfq_bfqq_to_bfqg()
>   block, bfq: avoid moving bfqq to it's parent bfqg
>   block, bfq: don't move oom_bfqq
> 
> [...]

Applied, thanks!

[1/3] block, bfq: cleanup bfq_bfqq_to_bfqg()
      commit: a9c77f6ec0b566439182a10b64dd3e60a0408849
[2/3] block, bfq: avoid moving bfqq to it's parent bfqg
      commit: 36ad7fe0ec7485ee435f7a40452c7a58598779d4
[3/3] block, bfq: don't move oom_bfqq
      commit: a0b98e6fba18a40aa9672cc3e0abf980456f3ae6

Best regards,
-- 
Jens Axboe

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[Jens Axboe]

On 1/28/22 7:45 AM, Jens Axboe wrote:
> On Fri, 31 Dec 2021 11:23:51 +0800, Yu Kuai wrote:
>> Chagnes in v2:
>>  - add comment in patch 2
>>  - remove patch 4, since the problem do not exist.
>>
>> Yu Kuai (3):
>>   block, bfq: cleanup bfq_bfqq_to_bfqg()
>>   block, bfq: avoid moving bfqq to it's parent bfqg
>>   block, bfq: don't move oom_bfqq
>>
>> [...]
> 
> Applied, thanks!
> 
> [1/3] block, bfq: cleanup bfq_bfqq_to_bfqg()
>       commit: a9c77f6ec0b566439182a10b64dd3e60a0408849
> [2/3] block, bfq: avoid moving bfqq to it's parent bfqg
>       commit: 36ad7fe0ec7485ee435f7a40452c7a58598779d4
> [3/3] block, bfq: don't move oom_bfqq
>       commit: a0b98e6fba18a40aa9672cc3e0abf980456f3ae6

For all those pings, this patchset sure didn't see a lot of compiles:

block/bfq-cgroup.c: In function ‘bfq_bfqq_move’:
block/bfq-cgroup.c:648:40: error: implicit declaration of function ‘bfq_group’; did you mean ‘bfqq_group’? [-Werror=implicit-function-declaration]
  648 |         struct bfq_group *old_parent = bfq_group(bfqq);
      |                                        ^~~~~~~~~
      |                                        bfqq_group
block/bfq-cgroup.c:648:40: error: initialization of ‘struct bfq_group *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
cc1: all warnings being treated as errors
make[1]: *** [scripts/Makefile.build:288: block/bfq-cgroup.o] Error 1
make: *** [Makefile:1831: block] Error 2

Dropped.

-- 
Jens Axboe

Re: [PATCH v2 0/3] block, bfq: minor cleanup and fix

[yukuai (C)]

在 2022/01/29 3:27, Jens Axboe 写道:
> On 1/28/22 7:45 AM, Jens Axboe wrote:
>> On Fri, 31 Dec 2021 11:23:51 +0800, Yu Kuai wrote:
>>> Chagnes in v2:
>>>   - add comment in patch 2
>>>   - remove patch 4, since the problem do not exist.
>>>
>>> Yu Kuai (3):
>>>    block, bfq: cleanup bfq_bfqq_to_bfqg()
>>>    block, bfq: avoid moving bfqq to it's parent bfqg
>>>    block, bfq: don't move oom_bfqq
>>>
>>> [...]
>>
>> Applied, thanks!
>>
>> [1/3] block, bfq: cleanup bfq_bfqq_to_bfqg()
>>        commit: a9c77f6ec0b566439182a10b64dd3e60a0408849
>> [2/3] block, bfq: avoid moving bfqq to it's parent bfqg
>>        commit: 36ad7fe0ec7485ee435f7a40452c7a58598779d4
>> [3/3] block, bfq: don't move oom_bfqq
>>        commit: a0b98e6fba18a40aa9672cc3e0abf980456f3ae6
> 
> For all those pings, this patchset sure didn't see a lot of compiles:
> 
> block/bfq-cgroup.c: In function ‘bfq_bfqq_move’:
> block/bfq-cgroup.c:648:40: error: implicit declaration of function ‘bfq_group’; did you mean ‘bfqq_group’? [-Werror=implicit-function-declaration]
>    648 |         struct bfq_group *old_parent = bfq_group(bfqq);
>        |                                        ^~~~~~~~~
>        |                                        bfqq_group
> block/bfq-cgroup.c:648:40: error: initialization of ‘struct bfq_group *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
> cc1: all warnings being treated as errors
> make[1]: *** [scripts/Makefile.build:288: block/bfq-cgroup.o] Error 1
> make: *** [Makefile:1831: block] Error 2
> 
> Dropped.
> 

Hi,

I'm sincerely sorry for this, I do forget to compiles this patchset,
and let this stupid clerical error exposure to you...

I'll send anothor version of patch 2.

Thanks,
Kuai