From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <00moses.alexander00@gmail.com> Return-Path: <00moses.alexander00@gmail.com> Date: Wed, 11 Apr 2018 12:12:56 +0200 From: Alexandru Moise <00moses.alexander00@gmail.com> To: Tejun Heo Cc: axboe@kernel.dk, shli@fb.com, nborisov@suse.com, arnd@arndb.de, gregkh@linuxfoundation.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Joseph Qi Subject: Re: [PATCH v2] blk-cgroup: remove entries in blkg_tree before queue release Message-ID: <20180411101242.GA2322@gmail.com> References: <20180407102148.GA9729@gmail.com> <20180409220938.GI3126663@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180409220938.GI3126663@devbig577.frc2.facebook.com> List-ID: 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@gmail.com> > > --- > > 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