block: make queue flags non-atomic

We can save some atomic ops in the IO path, if we clearly define
the rules of how to modify the queue flags.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 29 insertions, 4 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c5065e3d2ca9..8ca481cd7d73 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -408,6 +408,30 @@ struct request_queue
 #define QUEUE_FLAG_ELVSWITCH    8       /* don't use elevator, just do FIFO */
 #define QUEUE_FLAG_BIDI         9       /* queue supports bidi requests */
 
+static inline void queue_flag_set_unlocked(unsigned int flag,
+                                           struct request_queue *q)
+{
+        __set_bit(flag, &q->queue_flags);
+}
+
+static inline void queue_flag_set(unsigned int flag, struct request_queue *q)
+{
+        WARN_ON_ONCE(!spin_is_locked(q->queue_lock));
+        __set_bit(flag, &q->queue_flags);
+}
+
+static inline void queue_flag_clear_unlocked(unsigned int flag,
+                                             struct request_queue *q)
+{
+        __clear_bit(flag, &q->queue_flags);
+}
+
+static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
+{
+        WARN_ON_ONCE(!spin_is_locked(q->queue_lock));
+        __clear_bit(flag, &q->queue_flags);
+}
+
 enum {
         /*
          * Hardbarrier is supported with one of the following methods.
@@ -496,17 +520,17 @@ static inline int blk_queue_full(struct request_queue *q, int rw)
 static inline void blk_set_queue_full(struct request_queue *q, int rw)
 {
         if (rw == READ)
-                set_bit(QUEUE_FLAG_READFULL, &q->queue_flags);
+                queue_flag_set(QUEUE_FLAG_READFULL, q);
         else
-                set_bit(QUEUE_FLAG_WRITEFULL, &q->queue_flags);
+                queue_flag_set(QUEUE_FLAG_WRITEFULL, q);
 }
 
 static inline void blk_clear_queue_full(struct request_queue *q, int rw)
 {
         if (rw == READ)
-                clear_bit(QUEUE_FLAG_READFULL, &q->queue_flags);
+                queue_flag_clear(QUEUE_FLAG_READFULL, q);
         else
-                clear_bit(QUEUE_FLAG_WRITEFULL, &q->queue_flags);
+                queue_flag_clear(QUEUE_FLAG_WRITEFULL, q);
 }
 
 
@@ -626,6 +650,7 @@ extern void blk_start_queue(struct request_queue *q);
 extern void blk_stop_queue(struct request_queue *q);
 extern void blk_sync_queue(struct request_queue *q);
 extern void __blk_stop_queue(struct request_queue *q);
+extern void __blk_run_queue(struct request_queue *);
 extern void blk_run_queue(struct request_queue *);
 extern void blk_start_queueing(struct request_queue *);
 extern int blk_rq_map_user(struct request_queue *, struct request *, void __user *, unsigned long);