Hello, Tejun. 在 2026/9/29 08:42, Tejun Heo 写道: > Hello, Tao. > > On Thu, 24 Sep 2026 13:45:46 +0800, Tao Cui wrote: > >> - /* if user is overriding anything, maintain what was there */ >> - if (ioc->user_qos_params || ioc->user_cost_model) >> + /* if user is overriding anything, maintain what was there; the >> + * same while a BPF model is attached: the builtin coefficients >> + * are inert then, so stepping the profile is pointless >> + */ >> + if (ioc->user_qos_params || ioc->user_cost_model >> +#ifdef CONFIG_BLK_CGROUP_IOCOST_BPF >> + || rcu_dereference_protected(ioc->model, >> + lockdep_is_held(&ioc->lock)) >> +#endif >> + ) > > Can you add a helper which returns the model in use with a stub returning > NULL for !CONFIG_BLK_CGROUP_IOCOST_BPF? That'd remove most of the #ifdefs > including the one in this condition and the duplicated seq_printf() in > ioc_cost_model_prfill(). Done. ioc_model_in_use() and a locked variant return the model in use, with NULL stubs for !CONFIG_BLK_CGROUP_IOCOST_BPF; the autop condition, both calc paths, the pd callbacks and the prfill now call the helpers, and the duplicated seq_printf() is unified.
> >> + /* sub-page IO: nothing to transfer-price */ >> + if (!pages) >> + return 0; >> + /* zero transfer cost is a legal model; guard the division */ >> + if (!coeff) >> + return 0; >> + /* pages * coeff can wrap and dodge the clamp below */ >> + if (coeff > VTIME_PER_SEC || pages > VTIME_PER_SEC / coeff) >> + return VTIME_PER_SEC; >> + return min(pages * coeff, VTIME_PER_SEC); > > This can just be pages * coeff like the builtin. An overflow only skews > the met/missed accounting, same as a user-set linear coefficient, and it > also gets rid of the 64-bit division. > Done; the guards and the division are gone and the completion-time sizing is back to a plain pages * coeff, like the builtin. >> + bdevf = bdev_file_open_by_dev(new_decode_dev(ops->dev), >> + BLK_OPEN_READ, NULL, NULL); > > When the disk goes away, the model should be ejected completely. > ioc_rqos_exit() unbinds it but the open bdev file keeps the dead disk and > the driver module pinned until the link is destroyed. Can you drop all > device references on removal like hid_bpf_destroy_device() does and look > up the device like blkg_conf_open_bdev() does, with blkdev_get_no_open() > and disk_live() checked under rq_qos_mutex? The two attach issues bpf-ci > reported, the missing re-attach check in .reg and the missing disk_live() > check, are real. > Done. The struct file is gone: the attach looks the device up with blkdev_get_no_open() and checks disk_live() under rq_qos_mutex like blkg_conf_open_bdev(), .reg rejects re-attach via ops->q, and ioc_rqos_exit() ejects the model completely on removal, clearing the queue pointer. To keep the queue alive across detach, the attach now holds a no_open bdev reference, similar to hid_bpf's per-ops device reference but without a struct file or driver-module pin; the reference is dropped by whichever path detaches the model first, either ioc_rqos_exit() during removal or .unreg, and .unreg re-checks ops->q under rq_qos_mutex. That leaves one race: .unreg may observe a non-NULL ops->q before ioc_rqos_exit() clears it, then block on rq_qos_mutex while the ejection drops the last bdev reference. This looks analogous to hid_bpf's .unreg vs. destroy_device synchronization. Does that seem acceptable here too, or would you rather have .unreg own the final reference unconditionally? Thanks. Tao > Thanks. > > -- > tejun
