From 2995fa78e423d7193f3b57835f6c1c75006a0315 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Mon, 13 Jan 2014 19:37:54 -0500 Subject: dm sysfs: fix a module unload race This reverts commit be35f48610 ("dm: wait until embedded kobject is released before destroying a device") and provides an improved fix. The kobject release code that calls the completion must be placed in a non-module file, otherwise there is a module unload race (if the process calling dm_kobject_release is preempted and the DM module unloaded after the completion is triggered, but before dm_kobject_release returns). To fix this race, this patch moves the completion code to dm-builtin.c which is always compiled directly into the kernel if BLK_DEV_DM is selected. The patch introduces a new dm_kobject_holder structure, its purpose is to keep the completion and kobject in one place, so that it can be accessed from non-module code without the need to export the layout of struct mapped_device to that code. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- drivers/md/dm.c | 20 +++++--------------- 1 file changed, 5 insertions(+), 15 deletions(-) (limited to 'drivers/md/dm.c') diff --git a/drivers/md/dm.c b/drivers/md/dm.c index e290e72922a4..b49c76284241 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -200,11 +200,8 @@ struct mapped_device { /* forced geometry settings */ struct hd_geometry geometry; - /* sysfs handle */ - struct kobject kobj; - - /* wait until the kobject is released */ - struct completion kobj_completion; + /* kobject and completion */ + struct dm_kobject_holder kobj_holder; /* zero-length flush that will be cloned and submitted to targets */ struct bio flush_bio; @@ -2044,7 +2041,7 @@ static struct mapped_device *alloc_dev(int minor) init_waitqueue_head(&md->wait); INIT_WORK(&md->work, dm_wq_work); init_waitqueue_head(&md->eventq); - init_completion(&md->kobj_completion); + init_completion(&md->kobj_holder.completion); md->disk->major = _major; md->disk->first_minor = minor; @@ -2906,14 +2903,14 @@ struct gendisk *dm_disk(struct mapped_device *md) struct kobject *dm_kobject(struct mapped_device *md) { - return &md->kobj; + return &md->kobj_holder.kobj; } struct mapped_device *dm_get_from_kobject(struct kobject *kobj) { struct mapped_device *md; - md = container_of(kobj, struct mapped_device, kobj); + md = container_of(kobj, struct mapped_device, kobj_holder.kobj); if (test_bit(DMF_FREEING, &md->flags) || dm_deleting_md(md)) @@ -2923,13 +2920,6 @@ struct mapped_device *dm_get_from_kobject(struct kobject *kobj) return md; } -struct completion *dm_get_completion_from_kobject(struct kobject *kobj) -{ - struct mapped_device *md = container_of(kobj, struct mapped_device, kobj); - - return &md->kobj_completion; -} - int dm_suspended_md(struct mapped_device *md) { return test_bit(DMF_SUSPENDED, &md->flags); -- cgit v1.2.3