diff options
Diffstat (limited to 'block/blk-core.c')
| -rw-r--r-- | block/blk-core.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/block/blk-core.c b/block/blk-core.c index 991c1d6ef24..f2db628aa50 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -416,7 +416,8 @@ void blk_drain_queue(struct request_queue *q, bool drain_all) * In bypass mode, only the dispatch FIFO queue of @q is used. This * function makes @q enter bypass mode and drains all requests which were * throttled or issued before. On return, it's guaranteed that no request - * is being throttled or has ELVPRIV set. + * is being throttled or has ELVPRIV set and blk_queue_bypass() %true + * inside queue or RCU read lock. */ void blk_queue_bypass_start(struct request_queue *q) { @@ -426,6 +427,8 @@ void blk_queue_bypass_start(struct request_queue *q) spin_unlock_irq(q->queue_lock); blk_drain_queue(q, false); + /* ensure blk_queue_bypass() is %true inside RCU read lock */ + synchronize_rcu(); } EXPORT_SYMBOL_GPL(blk_queue_bypass_start); @@ -462,7 +465,15 @@ void blk_cleanup_queue(struct request_queue *q) spin_lock_irq(lock); - /* dead queue is permanently in bypass mode till released */ + /* + * Dead queue is permanently in bypass mode till released. Note + * that, unlike blk_queue_bypass_start(), we aren't performing + * synchronize_rcu() after entering bypass mode to avoid the delay + * as some drivers create and destroy a lot of queues while + * probing. This is still safe because blk_release_queue() will be + * called only after the queue refcnt drops to zero and nothing, + * RCU or not, would be traversing the queue by then. + */ q->bypass_depth++; queue_flag_set(QUEUE_FLAG_BYPASS, q); |