On Tue, Apr 18, 2017 at 04:29:42PM -0700, Bart Van Assche wrote: > A later patch in this series will modify blk_mq_debugfs_register() > such that it uses q->kobj.parent to determine the name of a > request queue. Hence make sure that that pointer is initialized > before blk_mq_debugfs_register() is called. To avoid lock inversion, > protect sysfs / debugfs registration with the queue sysfs_lock > instead of the global mutex all_q_mutex.
I think this is sane, I don't see why we would need all_q_mutex for this. One comment below, however. > Signed-off-by: Bart Van Assche <[email protected]> > Cc: Omar Sandoval <[email protected]> > Cc: Hannes Reinecke <[email protected]> > --- > block/blk-mq-sysfs.c | 43 +++++++++++++++++++++++++++++++++++-------- > block/blk-mq.h | 1 + > block/blk-sysfs.c | 6 +++--- > 3 files changed, 39 insertions(+), 11 deletions(-) > > diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c > index d745ab81033a..54ef9402914c 100644 > --- a/block/blk-mq-sysfs.c > +++ b/block/blk-mq-sysfs.c > @@ -253,6 +253,8 @@ static void __blk_mq_unregister_dev(struct device *dev, > struct request_queue *q) > struct blk_mq_hw_ctx *hctx; > int i; > > + lockdep_assert_held(&q->sysfs_lock); > + > queue_for_each_hw_ctx(q, hctx, i) > blk_mq_unregister_hctx(hctx); > > @@ -267,9 +269,9 @@ static void __blk_mq_unregister_dev(struct device *dev, > struct request_queue *q) > > void blk_mq_unregister_dev(struct device *dev, struct request_queue *q) > { > - blk_mq_disable_hotplug(); > + mutex_lock(&q->sysfs_lock); > __blk_mq_unregister_dev(dev, q); > - blk_mq_enable_hotplug(); > + mutex_unlock(&q->sysfs_lock); > } > > void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx) > @@ -302,12 +304,13 @@ void blk_mq_sysfs_init(struct request_queue *q) > } > } > > -int blk_mq_register_dev(struct device *dev, struct request_queue *q) > +int __blk_mq_register_dev(struct device *dev, struct request_queue *q) > { > struct blk_mq_hw_ctx *hctx; > int ret, i; > > - blk_mq_disable_hotplug(); > + WARN_ON_ONCE(!q->kobj.parent); > + lockdep_assert_held(&q->sysfs_lock); > > ret = kobject_add(&q->mq_kobj, kobject_get(&dev->kobj), "%s", "mq"); > if (ret < 0) > @@ -327,8 +330,20 @@ int blk_mq_register_dev(struct device *dev, struct > request_queue *q) > __blk_mq_unregister_dev(dev, q); > else > q->mq_sysfs_init_done = true; > + > out: > - blk_mq_enable_hotplug(); > + return ret; > +} > + > +int blk_mq_register_dev(struct device *dev, struct request_queue *q) > +{ > + int ret; > + > + ret = mutex_lock_interruptible(&q->sysfs_lock); Why did you make this interruptible? blk_mq_disable_hotplug() wasn't interruptible before, so now dm_mq_init_request_queue() can fail silently if it is interrupted.
