On Tue, 2018-04-10 at 20:10 -0600, Jens Axboe wrote: > On 4/10/18 8:05 PM, Ming Lei wrote: > > 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 <[email protected]> > > > Fixes: a063057d7c73 ("block: Fix a race between request queue removal and > > > the block cgroup controller") > > > Signed-off-by: Bart Van Assche <[email protected]> > > > Cc: Ming Lei <[email protected]> > > > Cc: Joseph Qi <[email protected]> > > > --- > > > 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'. > > That's a good point, the NULL check needs to be included first. Bart, > do you want to send an update? I can just rebase the for-linus branch.
But how could the request pointer be NULL? Which code clears that pointer? Thanks, Bart.
