From e9a823fb34a8b0fcba6e112aa1003258a1a5af50 Mon Sep 17 00:00:00 2001 From: David Jeffery Date: Mon, 28 Aug 2017 10:52:44 -0600 Subject: block: fix warning when I/O elevator is changed as request_queue is being removed There is a race between changing I/O elevator and request_queue removal which can trigger the warning in kobject_add_internal. A program can use sysfs to request a change of elevator at the same time another task is unregistering the request_queue the elevator would be attached to. The elevator's kobject will then attempt to be connected to the request_queue in the object tree when the request_queue has just been removed from sysfs. This triggers the warning in kobject_add_internal as the request_queue no longer has a sysfs directory: kobject_add_internal failed for iosched (error: -2 parent: queue) ------------[ cut here ]------------ WARNING: CPU: 3 PID: 14075 at lib/kobject.c:244 kobject_add_internal+0x103/0x2d0 To fix this warning, we can check the QUEUE_FLAG_REGISTERED flag when changing the elevator and use the request_queue's sysfs_lock to serialize between clearing the flag and the elevator testing the flag. Signed-off-by: David Jeffery Tested-by: Ming Lei Reviewed-by: Ming Lei Signed-off-by: Jens Axboe --- block/blk-sysfs.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'block/blk-sysfs.c') diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 27aceab1cc314..b8362c0df51d5 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -931,7 +931,9 @@ void blk_unregister_queue(struct gendisk *disk) if (WARN_ON(!q)) return; + mutex_lock(&q->sysfs_lock); queue_flag_clear_unlocked(QUEUE_FLAG_REGISTERED, q); + mutex_unlock(&q->sysfs_lock); wbt_exit(q); -- cgit v1.2.3