block: implement blk_queue_bypass_start/end()

Rename and extend elv_queisce_start/end() to
blk_queue_bypass_start/end() which are exported and supports nesting
via @q->bypass_depth.  Also add blk_queue_bypass() to test bypass
state.

This will be further extended and used for blkio_group management.

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, 4 insertions, 1 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 606cf339bb56..315db1d91bc4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -389,6 +389,8 @@ struct request_queue {
 
         struct mutex            sysfs_lock;
 
+        int                     bypass_depth;
+
 #if defined(CONFIG_BLK_DEV_BSG)
         bsg_job_fn              *bsg_job_fn;
         int                     bsg_job_size;
@@ -406,7 +408,7 @@ struct request_queue {
 #define QUEUE_FLAG_SYNCFULL     3       /* read queue has been filled */
 #define QUEUE_FLAG_ASYNCFULL    4       /* write queue has been filled */
 #define QUEUE_FLAG_DEAD         5       /* queue being torn down */
-#define QUEUE_FLAG_ELVSWITCH    6       /* don't use elevator, just do FIFO */
+#define QUEUE_FLAG_BYPASS       6       /* act as dumb FIFO queue */
 #define QUEUE_FLAG_BIDI         7       /* queue supports bidi requests */
 #define QUEUE_FLAG_NOMERGES     8       /* disable merge attempts */
 #define QUEUE_FLAG_SAME_COMP    9       /* complete on same CPU-group */
@@ -494,6 +496,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
 #define blk_queue_tagged(q)     test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
 #define blk_queue_stopped(q)    test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
 #define blk_queue_dead(q)       test_bit(QUEUE_FLAG_DEAD, &(q)->queue_flags)
+#define blk_queue_bypass(q)     test_bit(QUEUE_FLAG_BYPASS, &(q)->queue_flags)
 #define blk_queue_nomerges(q)   test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
 #define blk_queue_noxmerges(q)  \
         test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags)