Hi James, On 08/11/11 04:52, James Bottomley wrote: > On Wed, 2011-08-10 at 13:29 +0900, Jun'ichi Nomura wrote: >> 2 patches have been proposed but neither of them included: >> 1) Add QUEUE_FLAG_DEAD check in blk_insert_cloned_request() >> https://lkml.org/lkml/2011/7/8/457 >> 2) SCSI to call blk_cleanup_queue() from device's ->release() callback >> (before 2.6.39, it used to work like this) >> https://lkml.org/lkml/2011/7/2/106 > > Well, they both have documented objections. I asked why we destroy the > elevator in the del case and didn't get any traction, so let me show the > actual patch which should fix all of these issues. > > Is there a good reason for not doing this as a bug fix now? > > James > > --- > diff --git a/block/blk-core.c b/block/blk-core.c > index b627558..cc72b7d 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -367,11 +367,6 @@ void blk_cleanup_queue(struct request_queue *q) > queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q); > mutex_unlock(&q->sysfs_lock); > > - if (q->elevator) > - elevator_exit(q->elevator); > - > - blk_throtl_exit(q); > - > blk_put_queue(q); > } > EXPORT_SYMBOL(blk_cleanup_queue); > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index 0ee17b5..a5a756b 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -477,6 +477,11 @@ static void blk_release_queue(struct kobject *kobj) > > blk_sync_queue(q); > > + if (q->elevator) > + elevator_exit(q->elevator); > + > + blk_throtl_exit(q); > + > if (rl->rq_pool) > mempool_destroy(rl->rq_pool); I think it doesn't work because elevator_exit() and blk_throtl_exit() take &q->queue_lock, which may be freed by LLD after blk_cleanup_queue, before blk_release_queue. Vivek's comment here describes it in detail: https://lkml.org/lkml/2011/7/12/279 Vivek Goyal wrote: > I thought a driver could either rely on spin lock provided by request > queue or override that by providing its own spinlock. > > blk_init_allocated_queue_node() > /* Override internal queue lock with supplied lock pointer */ > if (lock) > q->queue_lock = lock; > So if driver calls blk_cleanup_queue() and drops its reference on queue, then > it should be free to release any memory it has allocated for spinlock. > So though queue is around there are no gurantees that q->queue_lock is > still around. That memory might have been freed by driver and reused. > > I see many drivers are providing their own locks. Some samples from > drivers/block. > > /virtio_blk.c: q = vblk->disk->queue = blk_init_queue(do_virtblk_request, > &vblk->lock); > ./xd.c: xd_queue = blk_init_queue(do_xd_request, &xd_lock); > ./cpqarray.c: q = blk_init_queue(do_ida_request, &hba[i]->lock); > ./sx8.c: q = blk_init_queue(carm_rq_fn, &host->lock); > ./sx8.c: q = blk_init_queue(carm_oob_rq_fn, &host->lock); > ./floppy.c: disks[dr]->queue = blk_init_queue(do_fd_request, &floppy_lock); > ./viodasd.c: q = blk_init_queue(do_viodasd_request, &d->q_lock); > ./cciss.c: disk->queue = blk_init_queue(do_cciss_request, &h->lock); > ./hd.c: hd_queue = blk_init_queue(do_hd_request, &hd_lock); > ./DAC960.c: RequestQueue = blk_init_queue(DAC960_RequestFunction,&Controller->queue_lock); > ./z2ram.c: z2_queue = blk_init_queue(do_z2_request, &z2ram_lock); > ./amiflop.c: disk->queue = blk_init_queue(do_fd_request, &amiflop_lock); > ./xen-blkfront.c: rq = blk_init_queue(do_blkif_request, &blkif_io_lock); > ./paride/pd.c: pd_queue = blk_init_queue(do_pd_request, &pd_lock); > ./paride/pf.c: pf_queue = blk_init_queue(do_pf_request, &pf_spin_lock); > ./paride/pcd.c: pcd_queue = blk_init_queue(do_pcd_request, &pcd_lock); > ./mg_disk.c: host->breq = blk_init_queue(mg_request_poll, &host->lock); > ./mg_disk.c: host->breq = blk_init_queue(mg_request, &host->lock); > ./rbd.c: q = blk_init_queue(rbd_rq_fn, &rbd_dev->lock); > ./sunvdc.c: q = blk_init_queue(do_vdc_request, &port->vio.lock); > ./swim.c: swd->queue = blk_init_queue(do_fd_request, &swd->lock); > ./xsysace.c: ace->queue = blk_init_queue(ace_request, &ace->lock); > ./osdblk.c: q = blk_init_queue(osdblk_rq_fn, &osdev->lock); > ./ps3disk.c: queue = blk_init_queue(ps3disk_request, &priv->lock); > ./swim3.c: swim3_queue = blk_init_queue(do_fd_request, &swim3_lock); > ./ub.c: if ((q = blk_init_queue(ub_request_fn, sc->lock)) == NULL) > ./nbd.c: disk->queue = blk_init_queue(do_nbd_request, &nbd_lock); # SCSI doesn't hit this problem because it uses # queue_lock embedded in struct request_queue. Thanks, -- Jun'ichi Nomura, NEC Corporation -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
