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authorMike Snitzer <snitzer@redhat.com>2018-01-11 20:11:01 +0100
committerJens Axboe <axboe@kernel.dk>2018-01-15 16:41:38 +0100
commit667257e8b2988c0183ba23e2bcd6900e87961606 (patch)
treeae0ec92e1fe69f71788169e07789096357f0c4ba /block/bio-integrity.c
parentblock: only bdi_unregister() in del_gendisk() if !GENHD_FL_HIDDEN (diff)
downloadlinux-667257e8b2988c0183ba23e2bcd6900e87961606.tar.xz
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block: properly protect the 'queue' kobj in blk_unregister_queue
The original commit e9a823fb34a8b (block: fix warning when I/O elevator is changed as request_queue is being removed) is pretty conflated. "conflated" because the resource being protected by q->sysfs_lock isn't the queue_flags (it is the 'queue' kobj). q->sysfs_lock serializes __elevator_change() (via elv_iosched_store) from racing with blk_unregister_queue(): 1) By holding q->sysfs_lock first, __elevator_change() can complete before a racing blk_unregister_queue(). 2) Conversely, __elevator_change() is testing for QUEUE_FLAG_REGISTERED in case elv_iosched_store() loses the race with blk_unregister_queue(), it needs a way to know the 'queue' kobj isn't there. Expand the scope of blk_unregister_queue()'s q->sysfs_lock use so it is held until after the 'queue' kobj is removed. To do so blk_mq_unregister_dev() must not also take q->sysfs_lock. So rename __blk_mq_unregister_dev() to blk_mq_unregister_dev(). Also, blk_unregister_queue() should use q->queue_lock to protect against any concurrent writes to q->queue_flags -- even though chances are the queue is being cleaned up so no concurrent writes are likely. Fixes: e9a823fb34a8b ("block: fix warning when I/O elevator is changed as request_queue is being removed") Signed-off-by: Mike Snitzer <snitzer@redhat.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bio-integrity.c')
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