block: reorganize throtl_get_tg() and blk_throtl_bio()

blk_throtl_bio() and throtl_get_tg() have rather unusual interface.

* throtl_get_tg() returns pointer to a valid tg or ERR_PTR(-ENODEV),
  and drops queue_lock in the latter case.  Different locking context
  depending on return value is error-prone and DEAD state is scheduled
  to be protected by queue_lock anyway.  Move DEAD check inside
  queue_lock and return valid tg or NULL.

* blk_throtl_bio() indicates return status both with its return value
  and in/out param **@bio.  The former is used to indicate whether
  queue is found to be dead during throtl processing.  The latter
  whether the bio is throttled.

  There's no point in returning DEAD check result from
  blk_throtl_bio().  The queue can die after blk_throtl_bio() is
  finished but before make_request_fn() grabs queue lock.

  Make it take *@bio instead and return boolean result indicating
  whether the request is throttled or not.

This patch doesn't cause any visible functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 3 insertions, 3 deletions

diff --git a/block/blk.h b/block/blk.h
index 2b66dc21a493..c018dba4e335 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -190,13 +190,13 @@ static inline int blk_do_io_stat(struct request *rq)
 }
 
 #ifdef CONFIG_BLK_DEV_THROTTLING
-extern int blk_throtl_bio(struct request_queue *q, struct bio **bio);
+extern bool blk_throtl_bio(struct request_queue *q, struct bio *bio);
 extern int blk_throtl_init(struct request_queue *q);
 extern void blk_throtl_exit(struct request_queue *q);
 #else /* CONFIG_BLK_DEV_THROTTLING */
-static inline int blk_throtl_bio(struct request_queue *q, struct bio **bio)
+static inline bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
 {
-        return 0;
+        return false;
 }
 static inline int blk_throtl_init(struct request_queue *q) { return 0; }
 static inline void blk_throtl_exit(struct request_queue *q) { }