diff --git a/drivers/block/loop.c b/drivers/block/loop.c index b1b05c45c07c..93137858b00c 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1006,10 +1006,10 @@ static int loop_configure(struct loop_device *lo, fmode_t mode, !file->f_op->write_iter) lo->lo_flags |= LO_FLAGS_READ_ONLY; - lo->workqueue = alloc_workqueue("loop%d", - WQ_UNBOUND | WQ_FREEZABLE, - 0, - lo->lo_number); + if (!lo->workqueue) + lo->workqueue = alloc_workqueue("loop%d", + WQ_UNBOUND | WQ_FREEZABLE, + 0, lo->lo_number); if (!lo->workqueue) { error = -ENOMEM; goto out_unlock; @@ -1082,7 +1082,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode, return error; } -static void __loop_clr_fd(struct loop_device *lo) +static void __loop_clr_fd(struct loop_device *lo, bool release) { struct file *filp; gfp_t gfp = lo->old_gfp_mask; @@ -1115,7 +1115,6 @@ static void __loop_clr_fd(struct loop_device *lo) /* freeze request queue during the transition */ blk_mq_freeze_queue(lo->lo_queue); - destroy_workqueue(lo->workqueue); spin_lock_irq(&lo->lo_work_lock); list_for_each_entry_safe(worker, pos, &lo->idle_worker_list, idle_list) { @@ -1144,6 +1143,8 @@ static void __loop_clr_fd(struct loop_device *lo) /* let user-space know about this change */ kobject_uevent(&disk_to_dev(lo->lo_disk)->kobj, KOBJ_CHANGE); mapping_set_gfp_mask(filp->f_mapping, gfp); + /* This is safe: open() is still holding a reference. */ + module_put(THIS_MODULE); blk_mq_unfreeze_queue(lo->lo_queue); disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE); @@ -1151,52 +1152,44 @@ static void __loop_clr_fd(struct loop_device *lo) if (lo->lo_flags & LO_FLAGS_PARTSCAN) { int err; - mutex_lock(&lo->lo_disk->open_mutex); + /* + * open_mutex has been held already in release path, so don't + * acquire it if this function is called in such case. + * + * If the reread partition isn't from release path, lo_refcnt + * must be at least one and it can only become zero when the + * current holder is released. + */ + if (!release) + mutex_lock(&lo->lo_disk->open_mutex); err = bdev_disk_changed(lo->lo_disk, false); - mutex_unlock(&lo->lo_disk->open_mutex); + if (!release) + mutex_unlock(&lo->lo_disk->open_mutex); if (err) pr_warn("%s: partition scan of loop%d failed (rc=%d)\n", __func__, lo->lo_number, err); /* Device is gone, no point in returning error */ } + /* + * lo->lo_state is set to Lo_unbound here after above partscan has + * finished. There cannot be anybody else entering __loop_clr_fd() as + * Lo_rundown state protects us from all the other places trying to + * change the 'lo' device. + */ lo->lo_flags = 0; if (!part_shift) lo->lo_disk->flags |= GENHD_FL_NO_PART; - - fput(filp); -} - -static void loop_rundown_completed(struct loop_device *lo) -{ mutex_lock(&lo->lo_mutex); lo->lo_state = Lo_unbound; mutex_unlock(&lo->lo_mutex); - module_put(THIS_MODULE); -} - -static void loop_rundown_workfn(struct work_struct *work) -{ - struct loop_device *lo = container_of(work, struct loop_device, - rundown_work); - struct block_device *bdev = lo->lo_device; - struct gendisk *disk = lo->lo_disk; - - __loop_clr_fd(lo); - kobject_put(&bdev->bd_device.kobj); - module_put(disk->fops->owner); - loop_rundown_completed(lo); -} -static void loop_schedule_rundown(struct loop_device *lo) -{ - struct block_device *bdev = lo->lo_device; - struct gendisk *disk = lo->lo_disk; - - __module_get(disk->fops->owner); - kobject_get(&bdev->bd_device.kobj); - INIT_WORK(&lo->rundown_work, loop_rundown_workfn); - queue_work(system_long_wq, &lo->rundown_work); + /* + * Need not hold lo_mutex to fput backing file. Calling fput holding + * lo_mutex triggers a circular lock dependency possibility warning as + * fput can take open_mutex which is usually taken before lo_mutex. + */ + fput(filp); } static int loop_clr_fd(struct loop_device *lo) @@ -1228,8 +1221,7 @@ static int loop_clr_fd(struct loop_device *lo) lo->lo_state = Lo_rundown; mutex_unlock(&lo->lo_mutex); - __loop_clr_fd(lo); - loop_rundown_completed(lo); + __loop_clr_fd(lo, false); return 0; } @@ -1754,7 +1746,7 @@ static void lo_release(struct gendisk *disk, fmode_t mode) * In autoclear mode, stop the loop thread * and remove configuration after last close. */ - loop_schedule_rundown(lo); + __loop_clr_fd(lo, true); return; } else if (lo->lo_state == Lo_bound) { /* @@ -2080,6 +2072,8 @@ static void loop_remove(struct loop_device *lo) mutex_unlock(&loop_ctl_mutex); /* There is no route which can find this loop device. */ mutex_destroy(&lo->lo_mutex); + if (lo->workqueue) + destroy_workqueue(lo->workqueue); kfree(lo); } diff --git a/drivers/block/loop.h b/drivers/block/loop.h index 918a7a2dc025..082d4b6bfc6a 100644 --- a/drivers/block/loop.h +++ b/drivers/block/loop.h @@ -56,7 +56,6 @@ struct loop_device { struct gendisk *lo_disk; struct mutex lo_mutex; bool idr_visible; - struct work_struct rundown_work; }; struct loop_cmd {