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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>
This commit is contained in:
Nick Piggin 2008-04-29 14:48:33 +02:00 committed by Jens Axboe
parent 68154e90c9
commit 75ad23bc0f
13 changed files with 101 additions and 48 deletions
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39
block/blk-core.c
View File

@ -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)

6
block/blk-merge.c
View File

@ -55,7 +55,7 @@ void blk_recalc_rq_segments(struct request *rq)
if (!rq->bio)
return;
cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
hw_seg_size = seg_size = 0;
phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
rq_for_each_segment(bv, rq, iter) {
@ -128,7 +128,7 @@ EXPORT_SYMBOL(blk_recount_segments);
static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
struct bio *nxt)
{
if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
return 0;
if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
@ -175,7 +175,7 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
int nsegs, cluster;
nsegs = 0;
cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
/*
* for each bio in rq

2
block/blk-settings.c
View File

@ -287,7 +287,7 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
t->max_segment_size = min(t->max_segment_size, b->max_segment_size);
t->hardsect_size = max(t->hardsect_size, b->hardsect_size);
if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
clear_bit(QUEUE_FLAG_CLUSTER, &t->queue_flags);
queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
}
EXPORT_SYMBOL(blk_queue_stack_limits);

8
block/blk-tag.c
View File

@ -70,7 +70,7 @@ void __blk_queue_free_tags(struct request_queue *q)
__blk_free_tags(bqt);
q->queue_tags = NULL;
q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
queue_flag_clear(QUEUE_FLAG_QUEUED, q);
}
/**
@ -98,7 +98,7 @@ EXPORT_SYMBOL(blk_free_tags);
**/
void blk_queue_free_tags(struct request_queue *q)
{
clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
queue_flag_clear(QUEUE_FLAG_QUEUED, q);
}
EXPORT_SYMBOL(blk_queue_free_tags);
@ -188,7 +188,7 @@ int blk_queue_init_tags(struct request_queue *q, int depth,
rc = blk_queue_resize_tags(q, depth);
if (rc)
return rc;
set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
queue_flag_set(QUEUE_FLAG_QUEUED, q);
return 0;
} else
atomic_inc(&tags->refcnt);
@ -197,7 +197,7 @@ int blk_queue_init_tags(struct request_queue *q, int depth,
* assign it, all done
*/
q->queue_tags = tags;
q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
queue_flag_set(QUEUE_FLAG_QUEUED, q);
INIT_LIST_HEAD(&q->tag_busy_list);
return 0;
fail:

13
block/elevator.c
View File

@ -1070,7 +1070,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
*/
spin_lock_irq(q->queue_lock);
set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
elv_drain_elevator(q);
@ -1104,7 +1104,10 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
* finally exit old elevator and turn off BYPASS.
*/
elevator_exit(old_elevator);
clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
spin_lock_irq(q->queue_lock);
queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
return 1;
fail_register:
@ -1115,7 +1118,11 @@ fail_register:
elevator_exit(e);
q->elevator = old_elevator;
elv_register_queue(q);
clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
spin_lock_irq(q->queue_lock);
queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
return 0;
}

2
drivers/block/loop.c
View File

@ -546,7 +546,7 @@ static void loop_unplug(struct request_queue *q)
{
struct loop_device *lo = q->queuedata;
clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);
queue_flag_clear_unlocked(QUEUE_FLAG_PLUGGED, q);
blk_run_address_space(lo->lo_backing_file->f_mapping);
}

2
drivers/block/ub.c
View File

@ -2399,7 +2399,7 @@ static void ub_disconnect(struct usb_interface *intf)
del_gendisk(lun->disk);
/*
* I wish I could do:
* set_bit(QUEUE_FLAG_DEAD, &q->queue_flags);
* queue_flag_set(QUEUE_FLAG_DEAD, q);
* As it is, we rely on our internal poisoning and let
* the upper levels to spin furiously failing all the I/O.
*/

7
drivers/md/dm-table.c
View File

@ -873,10 +873,13 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q)
q->max_hw_sectors = t->limits.max_hw_sectors;
q->seg_boundary_mask = t->limits.seg_boundary_mask;
q->bounce_pfn = t->limits.bounce_pfn;
/* XXX: the below will probably go bug. must ensure there can be no
* concurrency on queue_flags, and use the unlocked versions...
*/
if (t->limits.no_cluster)
q->queue_flags &= ~(1 << QUEUE_FLAG_CLUSTER);
queue_flag_clear(QUEUE_FLAG_CLUSTER, q);
else
q->queue_flags |= (1 << QUEUE_FLAG_CLUSTER);
queue_flag_set(QUEUE_FLAG_CLUSTER, q);
}

3
drivers/md/md.c
View File

@ -282,7 +282,8 @@ static mddev_t * mddev_find(dev_t unit)
kfree(new);
return NULL;
}
set_bit(QUEUE_FLAG_CLUSTER, &new->queue->queue_flags);
/* Can be unlocked because the queue is new: no concurrency */
queue_flag_set_unlocked(QUEUE_FLAG_CLUSTER, new->queue);
blk_queue_make_request(new->queue, md_fail_request);

2
drivers/scsi/scsi_debug.c
View File

@ -1773,7 +1773,7 @@ static int scsi_debug_slave_alloc(struct scsi_device *sdp)
if (SCSI_DEBUG_OPT_NOISE & scsi_debug_opts)
printk(KERN_INFO "scsi_debug: slave_alloc <%u %u %u %u>\n",
sdp->host->host_no, sdp->channel, sdp->id, sdp->lun);
set_bit(QUEUE_FLAG_BIDI, &sdp->request_queue->queue_flags);
queue_flag_set_unlocked(QUEUE_FLAG_BIDI, sdp->request_queue);
return 0;
}

29
drivers/scsi/scsi_lib.c
View File

@ -536,6 +536,9 @@ static void scsi_run_queue(struct request_queue *q)
!shost->host_blocked && !shost->host_self_blocked &&
!((shost->can_queue > 0) &&
(shost->host_busy >= shost->can_queue))) {
int flagset;
/*
* As long as shost is accepting commands and we have
* starved queues, call blk_run_queue. scsi_request_fn
@ -549,19 +552,20 @@ static void scsi_run_queue(struct request_queue *q)
sdev = list_entry(shost->starved_list.next,
struct scsi_device, starved_entry);
list_del_init(&sdev->starved_entry);
spin_unlock_irqrestore(shost->host_lock, flags);
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
flagset = test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
!test_bit(QUEUE_FLAG_REENTER,
&sdev->request_queue->queue_flags);
if (flagset)
queue_flag_set(QUEUE_FLAG_REENTER, sdev->request_queue);
__blk_run_queue(sdev->request_queue);
if (flagset)
queue_flag_clear(QUEUE_FLAG_REENTER, sdev->request_queue);
spin_unlock(sdev->request_queue->queue_lock);
if (test_bit(QUEUE_FLAG_REENTER, &q->queue_flags) &&
!test_and_set_bit(QUEUE_FLAG_REENTER,
&sdev->request_queue->queue_flags)) {
blk_run_queue(sdev->request_queue);
clear_bit(QUEUE_FLAG_REENTER,
&sdev->request_queue->queue_flags);
} else
blk_run_queue(sdev->request_queue);
spin_lock_irqsave(shost->host_lock, flags);
spin_lock(shost->host_lock);
if (unlikely(!list_empty(&sdev->starved_entry)))
/*
* sdev lost a race, and was put back on the
@ -1585,8 +1589,9 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
/* New queue, no concurrency on queue_flags */
if (!shost->use_clustering)
clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
queue_flag_clear_unlocked(QUEUE_FLAG_CLUSTER, q);
/*
* set a reasonable default alignment on word boundaries: the

3
drivers/scsi/scsi_transport_sas.c
View File

@ -248,8 +248,7 @@ static int sas_bsg_initialize(struct Scsi_Host *shost, struct sas_rphy *rphy)
else
q->queuedata = shost;
set_bit(QUEUE_FLAG_BIDI, &q->queue_flags);
queue_flag_set_unlocked(QUEUE_FLAG_BIDI, q);
return 0;
}

33
include/linux/blkdev.h
View File

@ -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);