@@ -196,6 +196,8 @@ struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
{
struct blkcg_gq *blkg;
+ WARN_ON_ONCE(!blk_entered_queue(q));
+
/*
* Hint didn't match. Look up from the radix tree. Note that the
* hint can only be updated under queue_lock as otherwise @blkg
@@ -389,6 +389,25 @@ struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
}
EXPORT_SYMBOL(blk_alloc_queue);
+#ifdef CONFIG_PROVE_LOCKING
+/**
+ * blk_entered_queue() - whether or not it is safe to access cgroup information
+ * @q: request queue pointer
+ *
+ * In order to avoid races between accessing cgroup information and the cgroup
+ * information removal from inside __blk_release_queue(), any code that accesses
+ * cgroup information must be protected by a blk_queue_enter()/blk_queue_exit()
+ * pair or must be called after queue cleanup progressed to a stage in which
+ * only the cleanup code accesses the queue.
+ */
+bool blk_entered_queue(struct request_queue *q)
+{
+ return percpu_ref_is_dying(&q->q_usage_counter) ||
+ !percpu_ref_is_zero(&q->q_usage_counter);
+}
+EXPORT_SYMBOL(blk_entered_queue);
+#endif
+
/**
* blk_queue_enter() - try to increase q->q_usage_counter
* @q: request queue pointer
@@ -878,6 +897,8 @@ generic_make_request_checks(struct bio *bio)
goto end_io;
}
+ WARN_ON_ONCE(!blk_entered_queue(q));
+
/*
* For a REQ_NOWAIT based request, return -EOPNOTSUPP
* if queue is not a request based queue.
@@ -358,6 +358,8 @@ static inline struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
{
struct blkcg_gq *blkg;
+ WARN_ON_ONCE(!blk_entered_queue(q));
+
if (blkcg == &blkcg_root)
return q->root_blkg;
@@ -856,6 +856,14 @@ extern int sg_scsi_ioctl(struct request_queue *, struct gendisk *, fmode_t,
extern int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags);
extern void blk_queue_exit(struct request_queue *q);
+#ifdef CONFIG_PROVE_LOCKING
+extern bool blk_entered_queue(struct request_queue *q);
+#else
+static inline bool blk_entered_queue(struct request_queue *q)
+{
+ return true;
+}
+#endif
extern void blk_sync_queue(struct request_queue *q);
extern int blk_rq_map_user(struct request_queue *, struct request *,
struct rq_map_data *, void __user *, unsigned long,
It is required to protect blkg_lookup() calls with a blk_queue_enter() / blk_queue_exit() pair. Since it is nontrivial to verify whether this is the case, verify this at runtime. Only perform this verification if CONFIG_LOCKDEP=y to avoid that unnecessary runtime overhead is added. Note: using lock_acquire()/lock_release() to verify whether blkg_lookup() is protected correctly is not possible since lock_acquire() and lock_release() must be called from the same task and since blk_queue_enter() and blk_queue_exit() can be called from different tasks. Suggested-by: Tejun Heo <tj@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> Cc: Alexandru Moise <00moses.alexander00@gmail.com> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> --- block/blk-cgroup.c | 2 ++ block/blk-core.c | 21 +++++++++++++++++++++ include/linux/blk-cgroup.h | 2 ++ include/linux/blkdev.h | 8 ++++++++ 4 files changed, 33 insertions(+)