On Mon, Apr 09, 2018 at 03:09:38PM -0700, Tejun Heo wrote:
> (cc'ing Joseph as he worked on the area recently, hi!)
>
> Hello,
>
> On Sat, Apr 07, 2018 at 12:21:48PM +0200, Alexandru Moise wrote:
> > The q->id is used as an index within the blkg_tree radix tree.
> >
> > If the entry is not released before reclaiming the blk_queue_ida's id
> > blkcg_init_queue() within a different driver from which this id
> > was originally for can fail due to the entry at that index within
> > the radix tree already existing.
> >
> > Signed-off-by: Alexandru Moise <00moses.alexander00@xxxxxxxxx>
> > ---
> > v2: Added no-op for !CONFIG_BLK_CGROUP
> >
> > block/blk-cgroup.c | 2 +-
> > block/blk-sysfs.c | 4 ++++
> > include/linux/blk-cgroup.h | 3 +++
> > 3 files changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> > index 1c16694ae145..224e937dbb59 100644
> > --- a/block/blk-cgroup.c
> > +++ b/block/blk-cgroup.c
> > @@ -369,7 +369,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
> > *
> > * Destroy all blkgs associated with @q.
> > */
> > -static void blkg_destroy_all(struct request_queue *q)
> > +void blkg_destroy_all(struct request_queue *q)
> > {
> > struct blkcg_gq *blkg, *n;
> >
> > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> > index d00d1b0ec109..a72866458f22 100644
> > --- a/block/blk-sysfs.c
> > +++ b/block/blk-sysfs.c
> > @@ -816,6 +816,10 @@ static void __blk_release_queue(struct work_struct *work)
> > if (q->bio_split)
> > bioset_free(q->bio_split);
> >
> > + spin_lock_irq(q->queue_lock);
> > + blkg_destroy_all(q);
> > + spin_unlock_irq(q->queue_lock);
> > +
> > ida_simple_remove(&blk_queue_ida, q->id);
> > call_rcu(&q->rcu_head, blk_free_queue_rcu);
>
> But we already do this through calling blkcg_exit_queue() from
> __blk_release_queue(). What's missing?
Hi,
It might be the jetlag but I can't see how you end up calling
blkcg_exit_queue() from __blk_release_queue().
As I see it the only way to reach blkcg_exit_queue() is from
blk_cleanup_queue(), which I don't see anywhere in __blk_release_queue().
I suspect that I'm just fixing a corner case though and
the general case is what you describe or similar.
../Alex
>
> Thanks.
>
> --
> tejun
