blk_mq_quiesce_queue() can not block dispatch in the following
two cases:
- direct issue or BLK_MQ_S_START_ON_RUN
- in theory, new RCU read-side critical sections may begin while
synchronize_rcu() was waiting, and end after returning of
synchronize_rcu().
so a new flag of QUEUE_FLAG_QUIESCED is introduced and evaluated
inside RCU read-side critical sections for fixing the above issues.
This patch fixes request use-after-free during canceling requets
of NVMe in nvme_dev_disable().
Signed-off-by: Ming Lei <ming....@redhat.com>
---
block/blk-mq.c | 33 ++++++++++++++++++++++++++++-----
include/linux/blkdev.h | 2 ++
2 files changed, 30 insertions(+), 5 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index a26fee3fb389..864709453c90 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -170,6 +170,10 @@ void blk_mq_quiesce_queue(struct request_queue *q)
__blk_mq_stop_hw_queues(q, true);
+ spin_lock_irq(q->queue_lock);
+ queue_flag_set(QUEUE_FLAG_QUIESCED, q);
+ spin_unlock_irq(q->queue_lock);
+
queue_for_each_hw_ctx(q, hctx, i) {
if (hctx->flags & BLK_MQ_F_BLOCKING)
synchronize_srcu(&hctx->queue_rq_srcu);
@@ -190,6 +194,10 @@ EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
*/
void blk_mq_unquiesce_queue(struct request_queue *q)
{
+ spin_lock_irq(q->queue_lock);
+ queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
+ spin_unlock_irq(q->queue_lock);
+
blk_mq_start_stopped_hw_queues(q, true);
}
EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
@@ -209,6 +217,9 @@ void blk_mq_wake_waiters(struct request_queue *q)
* the queue are notified as well.
*/
wake_up_all(&q->mq_freeze_wq);
+
+ /* Forcibly unquiesce the queue to avoid having stuck requests */
+ blk_mq_unquiesce_queue(q);
}
bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)
@@ -1108,13 +1119,15 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx
*hctx)
if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
rcu_read_lock();
- blk_mq_sched_dispatch_requests(hctx);
+ if (!blk_queue_quiesced(hctx->queue))
+ blk_mq_sched_dispatch_requests(hctx);
rcu_read_unlock();
} else {
might_sleep();
srcu_idx = srcu_read_lock(&hctx->queue_rq_srcu);
- blk_mq_sched_dispatch_requests(hctx);
+ if (!blk_queue_quiesced(hctx->queue))
+ blk_mq_sched_dispatch_requests(hctx);
srcu_read_unlock(&hctx->queue_rq_srcu, srcu_idx);
}
}
@@ -1519,9 +1532,14 @@ static void __blk_mq_try_issue_directly(struct request
*rq, blk_qc_t *cookie,
static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
struct request *rq, blk_qc_t *cookie)
{
- if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
+ bool blocking = hctx->flags & BLK_MQ_F_BLOCKING;
+ bool quiesced;
+
+ if (!blocking) {
rcu_read_lock();
- __blk_mq_try_issue_directly(rq, cookie, false);
+ quiesced = blk_queue_quiesced(rq->q);
+ if (!quiesced)
+ __blk_mq_try_issue_directly(rq, cookie, false);
rcu_read_unlock();
} else {
unsigned int srcu_idx;
@@ -1529,9 +1547,14 @@ static void blk_mq_try_issue_directly(struct
blk_mq_hw_ctx *hctx,
might_sleep();
srcu_idx = srcu_read_lock(&hctx->queue_rq_srcu);
- __blk_mq_try_issue_directly(rq, cookie, true);
+ quiesced = blk_queue_quiesced(rq->q);
+ if (!quiesced)
+ __blk_mq_try_issue_directly(rq, cookie, true);
srcu_read_unlock(&hctx->queue_rq_srcu, srcu_idx);
}
+
+ if (quiesced)
+ blk_mq_sched_insert_request(rq, false, false, false, blocking);
}
static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 41291be82ac4..60967797f4f6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -618,6 +618,7 @@ struct request_queue {
#define QUEUE_FLAG_STATS 27 /* track rq completion times */
#define QUEUE_FLAG_POLL_STATS 28 /* collecting stats for hybrid polling
*/
#define QUEUE_FLAG_REGISTERED 29 /* queue has been registered to a disk
*/
+#define QUEUE_FLAG_QUIESCED 30 /* queue has been quiesced */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -712,6 +713,7 @@ static inline void queue_flag_clear(unsigned int flag,
struct request_queue *q)
#define blk_noretry_request(rq) \
((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \
REQ_FAILFAST_DRIVER))
+#define blk_queue_quiesced(q) test_bit(QUEUE_FLAG_QUIESCED, &(q)->queue_flags)
static inline bool blk_account_rq(struct request *rq)
{
--
2.9.4
