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, 26 insertions, 13 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index e447799256d6..d2f23ec5ebfa 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -198,7 +198,8 @@ void blk_plug_device(struct request_queue *q)
         if (blk_queue_stopped(q))
                 return;
 
-        if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags)) {
+        if (!test_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags)) {
+                __set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);
                 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
                 blk_add_trace_generic(q, NULL, 0, BLK_TA_PLUG);
         }
@@ -213,9 +214,10 @@ int blk_remove_plug(struct request_queue *q)
 {
         WARN_ON(!irqs_disabled());
 
-        if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
+        if (!test_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
                 return 0;
 
+        queue_flag_clear(QUEUE_FLAG_PLUGGED, q);
         del_timer(&q->unplug_timer);
         return 1;
 }
@@ -311,15 +313,16 @@ void blk_start_queue(struct request_queue *q)
 {
         WARN_ON(!irqs_disabled());
 
-        clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
+        queue_flag_clear(QUEUE_FLAG_STOPPED, q);
 
         /*
          * one level of recursion is ok and is much faster than kicking
          * the unplug handling
          */
-        if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
+        if (!test_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
+                queue_flag_set(QUEUE_FLAG_REENTER, q);
                 q->request_fn(q);
-                clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
+                queue_flag_clear(QUEUE_FLAG_REENTER, q);
         } else {
                 blk_plug_device(q);
                 kblockd_schedule_work(&q->unplug_work);
@@ -344,7 +347,7 @@ EXPORT_SYMBOL(blk_start_queue);
 void blk_stop_queue(struct request_queue *q)
 {
         blk_remove_plug(q);
-        set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
+        queue_flag_set(QUEUE_FLAG_STOPPED, q);
 }
 EXPORT_SYMBOL(blk_stop_queue);
 
@@ -373,11 +376,8 @@ EXPORT_SYMBOL(blk_sync_queue);
  * blk_run_queue - run a single device queue
  * @q:  The queue to run
  */
-void blk_run_queue(struct request_queue *q)
+void __blk_run_queue(struct request_queue *q)
 {
-        unsigned long flags;
-
-        spin_lock_irqsave(q->queue_lock, flags);
         blk_remove_plug(q);
 
         /*
@@ -385,15 +385,28 @@ void blk_run_queue(struct request_queue *q)
          * handling reinvoke the handler shortly if we already got there.
          */
         if (!elv_queue_empty(q)) {
-                if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
+                if (!test_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
+                        queue_flag_set(QUEUE_FLAG_REENTER, q);
                         q->request_fn(q);
-                        clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
+                        queue_flag_clear(QUEUE_FLAG_REENTER, q);
                 } else {
                         blk_plug_device(q);
                         kblockd_schedule_work(&q->unplug_work);
                 }
         }
+}
+EXPORT_SYMBOL(__blk_run_queue);
 
+/**
+ * blk_run_queue - run a single device queue
+ * @q: The queue to run
+ */
+void blk_run_queue(struct request_queue *q)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(q->queue_lock, flags);
+        __blk_run_queue(q);
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
 EXPORT_SYMBOL(blk_run_queue);
@@ -406,7 +419,7 @@ void blk_put_queue(struct request_queue *q)
 void blk_cleanup_queue(struct request_queue *q)
 {
         mutex_lock(&q->sysfs_lock);
-        set_bit(QUEUE_FLAG_DEAD, &q->queue_flags);
+        queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
         mutex_unlock(&q->sysfs_lock);
 
         if (q->elevator)