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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>
This commit is contained in:
Tejun Heo 2012-03-05 13:14:58 -08:00 committed by Jens Axboe
parent b2fab5acd2
commit d732580b4e
4 changed files with 46 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
block/blk-core.c
View File

@ -409,6 +409,42 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
}
}
/**
* blk_queue_bypass_start - enter queue bypass mode
* @q: queue of interest
*
* In bypass mode, only the dispatch FIFO queue of @q is used. This
* function makes @q enter bypass mode and drains all requests which were
* issued before. On return, it's guaranteed that no request has ELVPRIV
* set.
*/
void blk_queue_bypass_start(struct request_queue *q)
{
spin_lock_irq(q->queue_lock);
q->bypass_depth++;
queue_flag_set(QUEUE_FLAG_BYPASS, q);
spin_unlock_irq(q->queue_lock);
blk_drain_queue(q, false);
}
EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
/**
* blk_queue_bypass_end - leave queue bypass mode
* @q: queue of interest
*
* Leave bypass mode and restore the normal queueing behavior.
*/
void blk_queue_bypass_end(struct request_queue *q)
{
spin_lock_irq(q->queue_lock);
if (!--q->bypass_depth)
queue_flag_clear(QUEUE_FLAG_BYPASS, q);
WARN_ON_ONCE(q->bypass_depth < 0);
spin_unlock_irq(q->queue_lock);
}
EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
/**
* blk_cleanup_queue - shutdown a request queue
* @q: request queue to shutdown
@ -862,8 +898,7 @@ retry:
* Also, lookup icq while holding queue_lock. If it doesn't exist,
* it will be created after releasing queue_lock.
*/
if (blk_rq_should_init_elevator(bio) &&
!test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags)) {
if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {
rw_flags |= REQ_ELVPRIV;
rl->elvpriv++;
if (et->icq_cache && ioc)

6
block/blk.h
View File

@ -23,7 +23,8 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
struct bio *bio);
int blk_rq_append_bio(struct request_queue *q, struct request *rq,
struct bio *bio);
void blk_drain_queue(struct request_queue *q, bool drain_all);
void blk_queue_bypass_start(struct request_queue *q);
void blk_queue_bypass_end(struct request_queue *q);
void blk_dequeue_request(struct request *rq);
void __blk_queue_free_tags(struct request_queue *q);
bool __blk_end_bidi_request(struct request *rq, int error,
@ -144,9 +145,6 @@ void blk_queue_congestion_threshold(struct request_queue *q);
int blk_dev_init(void);
void elv_quiesce_start(struct request_queue *q);
void elv_quiesce_end(struct request_queue *q);
/*
* Return the threshold (number of used requests) at which the queue is

25
block/elevator.c
View File

@ -553,25 +553,6 @@ void elv_drain_elevator(struct request_queue *q)
}
}
void elv_quiesce_start(struct request_queue *q)
{
if (!q->elevator)
return;
spin_lock_irq(q->queue_lock);
queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
blk_drain_queue(q, false);
}
void elv_quiesce_end(struct request_queue *q)
{
spin_lock_irq(q->queue_lock);
queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
}
void __elv_add_request(struct request_queue *q, struct request *rq, int where)
{
trace_block_rq_insert(q, rq);
@ -903,7 +884,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
* using INSERT_BACK. All requests have SOFTBARRIER set and no
* merge happens either.
*/
elv_quiesce_start(q);
blk_queue_bypass_start(q);
/* unregister and clear all auxiliary data of the old elevator */
if (registered)
@ -933,7 +914,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
/* done, kill the old one and finish */
elevator_exit(old);
elv_quiesce_end(q);
blk_queue_bypass_end(q);
blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
@ -945,7 +926,7 @@ fail_init:
/* switch failed, restore and re-register old elevator */
q->elevator = old;
elv_register_queue(q);
elv_quiesce_end(q);
blk_queue_bypass_end(q);
return err;
}

5
include/linux/blkdev.h
View File

@ -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)