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>
diff --git a/block/blk-core.c b/block/blk-core.c
index e447799..d2f23ec 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -198,7 +198,8 @@
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 @@
{
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 @@
{
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 @@
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 @@
* 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 @@
* 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_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)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index b5c5c4a..73b2356 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -55,7 +55,7 @@
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 @@
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 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
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 77b51dc..6089384 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -287,7 +287,7 @@
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);
diff --git a/block/blk-tag.c b/block/blk-tag.c
index 4780a46..e176ddb 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -70,7 +70,7 @@
__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 @@
**/
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 @@
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 @@
* 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:
diff --git a/block/elevator.c b/block/elevator.c
index 88318c3..e8a90fe 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -1070,7 +1070,7 @@
*/
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 @@
* 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 @@
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;
}
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index f7f1635..d3a25b0 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -546,7 +546,7 @@
{
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);
}
diff --git a/drivers/block/ub.c b/drivers/block/ub.c
index 27bfe72..e322cce 100644
--- a/drivers/block/ub.c
+++ b/drivers/block/ub.c
@@ -2399,7 +2399,7 @@
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.
*/
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 51be533..73326e7 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -873,10 +873,13 @@
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);
}
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 87620b7..acd716b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -282,7 +282,8 @@
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);
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 07103c3..f6600bf 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -1773,7 +1773,7 @@
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;
}
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 67f412b..d545ad1 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -536,6 +536,9 @@
!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 @@
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 @@
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
diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
index 7899e3d..f4461d3 100644
--- a/drivers/scsi/scsi_transport_sas.c
+++ b/drivers/scsi/scsi_transport_sas.c
@@ -248,8 +248,7 @@
else
q->queuedata = shost;
- set_bit(QUEUE_FLAG_BIDI, &q->queue_flags);
-
+ queue_flag_set_unlocked(QUEUE_FLAG_BIDI, q);
return 0;
}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c5065e3..8ca481c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -408,6 +408,30 @@
#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 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_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);