Re: [PATCH V3 0/2] block: fix race between adding wbt and normal IO

[Ming Lei <ming.lei@redhat.com>]

On Tue, Jun 15, 2021 at 05:55:20AM +0800, Ming Lei wrote:
> On Wed, Jun 09, 2021 at 09:58:20AM +0800, Ming Lei wrote:
> > Hello,
> > 
> > Yi reported several kernel panics on:
> > 
> > [16687.001777] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
> > ...
> > [16687.163549] pc : __rq_qos_track+0x38/0x60
> > 
> > or
> > 
> > [  997.690455] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
> > ...
> > [  997.850347] pc : __rq_qos_done+0x2c/0x50
> > 
> > Turns out it is caused by race between adding wbt and normal IO.
> > 
> > Fix the issue by freezing request queue when adding/deleting rq qos.
> > 
> > V3:
> > 	- use ->queue_lock for protecting concurrent adding/deleting rqos on
> > 	  same queue
> > 
> > V2:
> > 	- switch to the approach of freezing queue, which is more generic
> > 	  than V1.
> > 
> > 
> > 
> > Ming Lei (2):
> >   block: fix race between adding/removing rq qos and normal IO
> >   block: mark queue init done at the end of blk_register_queue
> > 
> >  block/blk-rq-qos.h | 24 ++++++++++++++++++++++++
> >  block/blk-sysfs.c  | 29 +++++++++++++++--------------
> >  2 files changed, 39 insertions(+), 14 deletions(-)
> > 
> > Cc: Yi Zhang <yi.zhang@redhat.com>
> > Cc: Bart Van Assche <bvanassche@acm.org>
> 
> Hello Jens,
> 
> Any chance to merge the fixes if you are fine?

Hi Jens,

Yi finds that the issue can be triggered in his more tests, and
has escalate it in RH BZ, can we fix the issue?


Thanks,
Ming