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| author | David Jeffery <djeffery@redhat.com> | 2017-08-28 18:52:44 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-08-28 18:52:44 +0200 |
| commit | e9a823fb34a8b0fcba6e112aa1003258a1a5af50 (patch) | |
| tree | dd6507e25c254a6aa569b0f5c5451bba04b415d4 | |
| parent | block, scheduler: convert xxx_var_store to void (diff) | |
| download | linux-e9a823fb34a8b0fcba6e112aa1003258a1a5af50.tar.xz linux-e9a823fb34a8b0fcba6e112aa1003258a1a5af50.zip | |
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 <djeffery@redhat.com>
Tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-sysfs.c | 2 | ||||
| -rw-r--r-- | block/elevator.c | 4 |
2 files changed, 6 insertions, 0 deletions
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 27aceab1cc31..b8362c0df51d 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); diff --git a/block/elevator.c b/block/elevator.c index 4bb2f0c93fa6..153926a90901 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -1055,6 +1055,10 @@ static int __elevator_change(struct request_queue *q, const char *name) char elevator_name[ELV_NAME_MAX]; struct elevator_type *e; + /* Make sure queue is not in the middle of being removed */ + if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags)) + return -ENOENT; + /* * Special case for mq, turn off scheduling */ |