On Tue, Apr 10, 2018 at 02:30:35PM -0600, Bart Van Assche wrote: > Because blkcg_exit_queue() is now called from inside blk_cleanup_queue() > it is no longer safe to access cgroup information during or after the > blk_cleanup_queue() call. Hence protect the generic_make_request_checks() > call with blk_queue_enter() / blk_queue_exit(). > > Reported-by: Ming Lei <ming.lei@xxxxxxxxxx> > Fixes: a063057d7c73 ("block: Fix a race between request queue removal and the block cgroup controller") > Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxx> > Cc: Ming Lei <ming.lei@xxxxxxxxxx> > Cc: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx> > --- > block/blk-core.c | 32 ++++++++++++++++++++++++++------ > 1 file changed, 26 insertions(+), 6 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index 34e2f2227fd9..a330cd2829e1 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -2386,8 +2386,19 @@ blk_qc_t generic_make_request(struct bio *bio) > * yet. > */ > struct bio_list bio_list_on_stack[2]; > + blk_mq_req_flags_t flags = bio->bi_opf & REQ_NOWAIT ? > + BLK_MQ_REQ_NOWAIT : 0; > + struct request_queue *q = bio->bi_disk->queue; > blk_qc_t ret = BLK_QC_T_NONE; > > + if (blk_queue_enter(q, flags) < 0) { As I mentioned last time, the queue pointer has to be checked before calling blk_queue_enter(), since it isn't difficult to trigger the failure log of 'generic_make_request: Trying to access nonexistent block-device'. -- Ming