On Sat, Apr 12, 2025 at 12:50:10AM +0530, Nilay Shroff wrote:
>
>
> On 4/10/25 7:00 PM, Ming Lei wrote:
> > +int elevator_change_done(struct request_queue *q, struct elev_change_ctx *ctx)
> > +{
> > + int ret = 0;
> > +
> > + if (ctx->old) {
> > + elv_unregister_queue(q, ctx->old);
> > + kobject_put(&ctx->old->kobj);
> > + }
> > + if (ctx->new) {
> > + ret = elv_register_queue(q, ctx->new, ctx->uevent);
> > + if (ret) {
> > + unsigned memflags = blk_mq_freeze_queue(q);
> > +
> > + mutex_lock(&q->elevator_lock);
> > + elevator_exit(q);
> > + mutex_unlock(&q->elevator_lock);
> > + blk_mq_unfreeze_queue(q, memflags);
> > + }
> > + }
> > + return 0;
> > +}
> > +
> We could have sysf elevator attributes simultaneously accessed while this function
> adds/removes sysfs elevator attributes without any protection. In fact, the show/store
> methods of elevator attributes runs with e->sysfs_lock held. So it seems moving
> the above function out of lock protection might cause crash or other side effects?
sysfs/kobject provides such protection, and kobject_del() will drain any
in-flight attribute access.
Thanks,
Ming
