diff options
| author | Ming Lei <ming.lei@redhat.com> | 2019-09-12 06:02:24 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-09-12 15:13:22 +0200 |
| commit | 0a67b5a926e63ff5492c3c675eab5900580d056d (patch) | |
| tree | 46b1761c8dc89e466d14e20abd659a3e76a1ca24 | |
| parent | scsi: core: remove dummy q->dev check (diff) | |
| download | linux-0a67b5a926e63ff5492c3c675eab5900580d056d.tar.xz linux-0a67b5a926e63ff5492c3c675eab5900580d056d.zip | |
block: fix race between switching elevator and removing queues
cecf5d87ff20 ("block: split .sysfs_lock into two locks") starts to
release & actuire sysfs_lock again during switching elevator. So it
isn't enough to prevent switching elevator from happening by simply
clearing QUEUE_FLAG_REGISTERED with holding sysfs_lock, because
in-progress switch still can move on after re-acquiring the lock,
meantime the flag of QUEUE_FLAG_REGISTERED won't get checked.
Fixes this issue by checking 'q->elevator' directly & locklessly after
q->kobj is removed in blk_unregister_queue(), this way is safe because
q->elevator can't be changed at that time.
Fixes: cecf5d87ff20 ("block: split .sysfs_lock into two locks")
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-sysfs.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 107513495220..3af79831e717 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -1030,7 +1030,6 @@ EXPORT_SYMBOL_GPL(blk_register_queue); void blk_unregister_queue(struct gendisk *disk) { struct request_queue *q = disk->queue; - bool has_elevator; if (WARN_ON(!q)) return; @@ -1046,7 +1045,6 @@ void blk_unregister_queue(struct gendisk *disk) */ mutex_lock(&q->sysfs_lock); blk_queue_flag_clear(QUEUE_FLAG_REGISTERED, q); - has_elevator = !!q->elevator; mutex_unlock(&q->sysfs_lock); mutex_lock(&q->sysfs_dir_lock); @@ -1061,7 +1059,11 @@ void blk_unregister_queue(struct gendisk *disk) kobject_del(&q->kobj); blk_trace_remove_sysfs(disk_to_dev(disk)); - if (has_elevator) + /* + * q->kobj has been removed, so it is safe to check if elevator + * exists without holding q->sysfs_lock. + */ + if (q->elevator) elv_unregister_queue(q); mutex_unlock(&q->sysfs_dir_lock); |