dm: add full blk-mq support to request-based DM
Commit e5863d9ad ("dm: allocate requests in target when stacking on
blk-mq devices") served as the first step toward fully utilizing blk-mq
in request-based DM -- it enabled stacking an old-style (request_fn)
request_queue ontop of the underlying blk-mq device(s). That first step
didn't improve performance of DM multipath ontop of fast blk-mq devices
(e.g. NVMe) because the top-level old-style request_queue was severely
limited by the queue_lock.
The second step offered here enables stacking a blk-mq request_queue
ontop of the underlying blk-mq device(s). This unlocks significant
performance gains on fast blk-mq devices, Keith Busch tested on his NVMe
testbed and offered this really positive news:
"Just providing a performance update. All my fio tests are getting
roughly equal performance whether accessed through the raw block
device or the multipath device mapper (~470k IOPS). I could only push
~20% of the raw iops through dm before this conversion, so this latest
tree is looking really solid from a performance standpoint."
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Tested-by: Keith Busch <keith.busch@intel.com>
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index add6391..c8f07e5 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1703,7 +1703,7 @@
*---------------------------------------------------------------*/
static struct target_type multipath_target = {
.name = "multipath",
- .version = {1, 8, 0},
+ .version = {1, 9, 0},
.module = THIS_MODULE,
.ctr = multipath_ctr,
.dtr = multipath_dtr,
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 0573120..66600ca 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -18,6 +18,7 @@
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/atomic.h>
+#include <linux/blk-mq.h>
#define DM_MSG_PREFIX "table"
@@ -1695,9 +1696,13 @@
md = dm_table_get_md(t);
queue = dm_get_md_queue(md);
if (queue) {
- spin_lock_irqsave(queue->queue_lock, flags);
- blk_run_queue_async(queue);
- spin_unlock_irqrestore(queue->queue_lock, flags);
+ if (queue->mq_ops)
+ blk_mq_run_hw_queues(queue, true);
+ else {
+ spin_lock_irqsave(queue->queue_lock, flags);
+ blk_run_queue_async(queue);
+ spin_unlock_irqrestore(queue->queue_lock, flags);
+ }
}
}
EXPORT_SYMBOL(dm_table_run_md_queue_async);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 5294e01..3a66baa 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -23,6 +23,7 @@
#include <linux/kthread.h>
#include <linux/ktime.h>
#include <linux/elevator.h> /* for rq_end_sector() */
+#include <linux/blk-mq.h>
#include <trace/events/block.h>
@@ -224,6 +225,9 @@
int last_rq_rw;
sector_t last_rq_pos;
ktime_t last_rq_start_time;
+
+ /* for blk-mq request-based DM support */
+ struct blk_mq_tag_set tag_set;
};
/*
@@ -1025,6 +1029,11 @@
blk_update_request(tio->orig, 0, nr_bytes);
}
+static struct dm_rq_target_io *tio_from_request(struct request *rq)
+{
+ return (rq->q->mq_ops ? blk_mq_rq_to_pdu(rq) : rq->special);
+}
+
/*
* Don't touch any member of the md after calling this function because
* the md may be freed in dm_put() at the end of this function.
@@ -1048,8 +1057,10 @@
* queue lock again.
*/
if (run_queue) {
- if (!nr_requests_pending ||
- (nr_requests_pending >= md->queue->nr_congestion_on))
+ if (md->queue->mq_ops)
+ blk_mq_run_hw_queues(md->queue, true);
+ else if (!nr_requests_pending ||
+ (nr_requests_pending >= md->queue->nr_congestion_on))
blk_run_queue_async(md->queue);
}
@@ -1062,13 +1073,17 @@
static void free_rq_clone(struct request *clone)
{
struct dm_rq_target_io *tio = clone->end_io_data;
+ struct mapped_device *md = tio->md;
blk_rq_unprep_clone(clone);
+
if (clone->q && clone->q->mq_ops)
tio->ti->type->release_clone_rq(clone);
else
- free_clone_request(tio->md, clone);
- free_rq_tio(tio);
+ free_clone_request(md, clone);
+
+ if (!md->queue->mq_ops)
+ free_rq_tio(tio);
}
/*
@@ -1097,17 +1112,22 @@
}
free_rq_clone(clone);
- blk_end_request_all(rq, error);
+ if (!rq->q->mq_ops)
+ blk_end_request_all(rq, error);
+ else
+ blk_mq_end_request(rq, error);
rq_completed(md, rw, true);
}
static void dm_unprep_request(struct request *rq)
{
- struct dm_rq_target_io *tio = rq->special;
+ struct dm_rq_target_io *tio = tio_from_request(rq);
struct request *clone = tio->clone;
- rq->special = NULL;
- rq->cmd_flags &= ~REQ_DONTPREP;
+ if (!rq->q->mq_ops) {
+ rq->special = NULL;
+ rq->cmd_flags &= ~REQ_DONTPREP;
+ }
if (clone)
free_rq_clone(clone);
@@ -1116,18 +1136,29 @@
/*
* Requeue the original request of a clone.
*/
-static void dm_requeue_unmapped_original_request(struct mapped_device *md,
- struct request *rq)
+static void old_requeue_request(struct request *rq)
{
- int rw = rq_data_dir(rq);
struct request_queue *q = rq->q;
unsigned long flags;
- dm_unprep_request(rq);
-
spin_lock_irqsave(q->queue_lock, flags);
blk_requeue_request(q, rq);
spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+static void dm_requeue_unmapped_original_request(struct mapped_device *md,
+ struct request *rq)
+{
+ int rw = rq_data_dir(rq);
+
+ dm_unprep_request(rq);
+
+ if (!rq->q->mq_ops)
+ old_requeue_request(rq);
+ else {
+ blk_mq_requeue_request(rq);
+ blk_mq_kick_requeue_list(rq->q);
+ }
rq_completed(md, rw, false);
}
@@ -1139,33 +1170,42 @@
dm_requeue_unmapped_original_request(tio->md, tio->orig);
}
-static void __stop_queue(struct request_queue *q)
+static void old_stop_queue(struct request_queue *q)
{
+ unsigned long flags;
+
+ if (blk_queue_stopped(q))
+ return;
+
+ spin_lock_irqsave(q->queue_lock, flags);
blk_stop_queue(q);
+ spin_unlock_irqrestore(q->queue_lock, flags);
}
static void stop_queue(struct request_queue *q)
{
+ if (!q->mq_ops)
+ old_stop_queue(q);
+ else
+ blk_mq_stop_hw_queues(q);
+}
+
+static void old_start_queue(struct request_queue *q)
+{
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
- __stop_queue(q);
- spin_unlock_irqrestore(q->queue_lock, flags);
-}
-
-static void __start_queue(struct request_queue *q)
-{
if (blk_queue_stopped(q))
blk_start_queue(q);
+ spin_unlock_irqrestore(q->queue_lock, flags);
}
static void start_queue(struct request_queue *q)
{
- unsigned long flags;
-
- spin_lock_irqsave(q->queue_lock, flags);
- __start_queue(q);
- spin_unlock_irqrestore(q->queue_lock, flags);
+ if (!q->mq_ops)
+ old_start_queue(q);
+ else
+ blk_mq_start_stopped_hw_queues(q, true);
}
static void dm_done(struct request *clone, int error, bool mapped)
@@ -1206,13 +1246,20 @@
static void dm_softirq_done(struct request *rq)
{
bool mapped = true;
- struct dm_rq_target_io *tio = rq->special;
+ struct dm_rq_target_io *tio = tio_from_request(rq);
struct request *clone = tio->clone;
+ int rw;
if (!clone) {
- blk_end_request_all(rq, tio->error);
- rq_completed(tio->md, rq_data_dir(rq), false);
- free_rq_tio(tio);
+ rw = rq_data_dir(rq);
+ if (!rq->q->mq_ops) {
+ blk_end_request_all(rq, tio->error);
+ rq_completed(tio->md, rw, false);
+ free_rq_tio(tio);
+ } else {
+ blk_mq_end_request(rq, tio->error);
+ rq_completed(tio->md, rw, false);
+ }
return;
}
@@ -1228,7 +1275,7 @@
*/
static void dm_complete_request(struct request *rq, int error)
{
- struct dm_rq_target_io *tio = rq->special;
+ struct dm_rq_target_io *tio = tio_from_request(rq);
tio->error = error;
blk_complete_request(rq);
@@ -1247,7 +1294,7 @@
}
/*
- * Called with the clone's queue lock held
+ * Called with the clone's queue lock held (for non-blk-mq)
*/
static void end_clone_request(struct request *clone, int error)
{
@@ -1808,6 +1855,18 @@
static void map_tio_request(struct kthread_work *work);
+static void init_tio(struct dm_rq_target_io *tio, struct request *rq,
+ struct mapped_device *md)
+{
+ tio->md = md;
+ tio->ti = NULL;
+ tio->clone = NULL;
+ tio->orig = rq;
+ tio->error = 0;
+ memset(&tio->info, 0, sizeof(tio->info));
+ init_kthread_work(&tio->work, map_tio_request);
+}
+
static struct dm_rq_target_io *prep_tio(struct request *rq,
struct mapped_device *md, gfp_t gfp_mask)
{
@@ -1819,13 +1878,7 @@
if (!tio)
return NULL;
- tio->md = md;
- tio->ti = NULL;
- tio->clone = NULL;
- tio->orig = rq;
- tio->error = 0;
- memset(&tio->info, 0, sizeof(tio->info));
- init_kthread_work(&tio->work, map_tio_request);
+ init_tio(tio, rq, md);
table = dm_get_live_table(md, &srcu_idx);
if (!dm_table_mq_request_based(table)) {
@@ -1869,11 +1922,11 @@
* DM_MAPIO_REQUEUE : the original request needs to be requeued
* < 0 : the request was completed due to failure
*/
-static int map_request(struct dm_target *ti, struct request *rq,
+static int map_request(struct dm_rq_target_io *tio, struct request *rq,
struct mapped_device *md)
{
int r;
- struct dm_rq_target_io *tio = rq->special;
+ struct dm_target *ti = tio->ti;
struct request *clone = NULL;
if (tio->clone) {
@@ -1888,7 +1941,7 @@
}
if (IS_ERR(clone))
return DM_MAPIO_REQUEUE;
- if (setup_clone(clone, rq, tio, GFP_KERNEL)) {
+ if (setup_clone(clone, rq, tio, GFP_NOIO)) {
/* -ENOMEM */
ti->type->release_clone_rq(clone);
return DM_MAPIO_REQUEUE;
@@ -1929,13 +1982,16 @@
struct request *rq = tio->orig;
struct mapped_device *md = tio->md;
- if (map_request(tio->ti, rq, md) == DM_MAPIO_REQUEUE)
+ if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE)
dm_requeue_unmapped_original_request(md, rq);
}
static void dm_start_request(struct mapped_device *md, struct request *orig)
{
- blk_start_request(orig);
+ if (!orig->q->mq_ops)
+ blk_start_request(orig);
+ else
+ blk_mq_start_request(orig);
atomic_inc(&md->pending[rq_data_dir(orig)]);
if (md->seq_rq_merge_deadline_usecs) {
@@ -2045,7 +2101,7 @@
dm_start_request(md, rq);
- tio = rq->special;
+ tio = tio_from_request(rq);
/* Establish tio->ti before queuing work (map_tio_request) */
tio->ti = ti;
queue_kthread_work(&md->kworker, &tio->work);
@@ -2142,7 +2198,7 @@
{
/*
* Request-based dm devices cannot be stacked on top of bio-based dm
- * devices. The type of this dm device has not been decided yet.
+ * devices. The type of this dm device may not have been decided yet.
* The type is decided at the first table loading time.
* To prevent problematic device stacking, clear the queue flag
* for request stacking support until then.
@@ -2150,7 +2206,15 @@
* This queue is new, so no concurrency on the queue_flags.
*/
queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, md->queue);
+}
+static void dm_init_old_md_queue(struct mapped_device *md)
+{
+ dm_init_md_queue(md);
+
+ /*
+ * Initialize aspects of queue that aren't relevant for blk-mq
+ */
md->queue->queuedata = md;
md->queue->backing_dev_info.congested_fn = dm_any_congested;
md->queue->backing_dev_info.congested_data = md;
@@ -2273,6 +2337,7 @@
static void free_dev(struct mapped_device *md)
{
int minor = MINOR(disk_devt(md->disk));
+ bool using_blk_mq = !!md->queue->mq_ops;
unlock_fs(md);
destroy_workqueue(md->wq);
@@ -2298,6 +2363,8 @@
del_gendisk(md->disk);
put_disk(md->disk);
blk_cleanup_queue(md->queue);
+ if (using_blk_mq)
+ blk_mq_free_tag_set(&md->tag_set);
bdput(md->bdev);
free_minor(minor);
@@ -2457,7 +2524,7 @@
* This must be done before setting the queue restrictions,
* because request-based dm may be run just after the setting.
*/
- if (dm_table_request_based(t) && !blk_queue_stopped(q))
+ if (dm_table_request_based(t))
stop_queue(q);
__bind_mempools(md, t);
@@ -2539,14 +2606,6 @@
return md->type;
}
-static bool dm_md_type_request_based(struct mapped_device *md)
-{
- unsigned table_type = dm_get_md_type(md);
-
- return (table_type == DM_TYPE_REQUEST_BASED ||
- table_type == DM_TYPE_MQ_REQUEST_BASED);
-}
-
struct target_type *dm_get_immutable_target_type(struct mapped_device *md)
{
return md->immutable_target_type;
@@ -2563,6 +2622,14 @@
}
EXPORT_SYMBOL_GPL(dm_get_queue_limits);
+static void init_rq_based_worker_thread(struct mapped_device *md)
+{
+ /* Initialize the request-based DM worker thread */
+ init_kthread_worker(&md->kworker);
+ md->kworker_task = kthread_run(kthread_worker_fn, &md->kworker,
+ "kdmwork-%s", dm_device_name(md));
+}
+
/*
* Fully initialize a request-based queue (->elevator, ->request_fn, etc).
*/
@@ -2571,29 +2638,131 @@
struct request_queue *q = NULL;
if (md->queue->elevator)
- return 1;
+ return 0;
/* Fully initialize the queue */
q = blk_init_allocated_queue(md->queue, dm_request_fn, NULL);
if (!q)
- return 0;
+ return -EINVAL;
/* disable dm_request_fn's merge heuristic by default */
md->seq_rq_merge_deadline_usecs = 0;
md->queue = q;
- dm_init_md_queue(md);
+ dm_init_old_md_queue(md);
blk_queue_softirq_done(md->queue, dm_softirq_done);
blk_queue_prep_rq(md->queue, dm_prep_fn);
- /* Also initialize the request-based DM worker thread */
- init_kthread_worker(&md->kworker);
- md->kworker_task = kthread_run(kthread_worker_fn, &md->kworker,
- "kdmwork-%s", dm_device_name(md));
+ init_rq_based_worker_thread(md);
elv_register_queue(md->queue);
- return 1;
+ return 0;
+}
+
+static int dm_mq_init_request(void *data, struct request *rq,
+ unsigned int hctx_idx, unsigned int request_idx,
+ unsigned int numa_node)
+{
+ struct mapped_device *md = data;
+ struct dm_rq_target_io *tio = blk_mq_rq_to_pdu(rq);
+
+ /*
+ * Must initialize md member of tio, otherwise it won't
+ * be available in dm_mq_queue_rq.
+ */
+ tio->md = md;
+
+ return 0;
+}
+
+static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
+ const struct blk_mq_queue_data *bd)
+{
+ struct request *rq = bd->rq;
+ struct dm_rq_target_io *tio = blk_mq_rq_to_pdu(rq);
+ struct mapped_device *md = tio->md;
+ int srcu_idx;
+ struct dm_table *map = dm_get_live_table(md, &srcu_idx);
+ struct dm_target *ti;
+ sector_t pos;
+
+ /* always use block 0 to find the target for flushes for now */
+ pos = 0;
+ if (!(rq->cmd_flags & REQ_FLUSH))
+ pos = blk_rq_pos(rq);
+
+ ti = dm_table_find_target(map, pos);
+ if (!dm_target_is_valid(ti)) {
+ dm_put_live_table(md, srcu_idx);
+ DMERR_LIMIT("request attempted access beyond the end of device");
+ /*
+ * Must perform setup, that rq_completed() requires,
+ * before returning BLK_MQ_RQ_QUEUE_ERROR
+ */
+ dm_start_request(md, rq);
+ return BLK_MQ_RQ_QUEUE_ERROR;
+ }
+ dm_put_live_table(md, srcu_idx);
+
+ if (ti->type->busy && ti->type->busy(ti))
+ return BLK_MQ_RQ_QUEUE_BUSY;
+
+ dm_start_request(md, rq);
+
+ /* Init tio using md established in .init_request */
+ init_tio(tio, rq, md);
+
+ /* Establish tio->ti before queuing work (map_tio_request) */
+ tio->ti = ti;
+ queue_kthread_work(&md->kworker, &tio->work);
+
+ return BLK_MQ_RQ_QUEUE_OK;
+}
+
+static struct blk_mq_ops dm_mq_ops = {
+ .queue_rq = dm_mq_queue_rq,
+ .map_queue = blk_mq_map_queue,
+ .complete = dm_softirq_done,
+ .init_request = dm_mq_init_request,
+};
+
+static int dm_init_request_based_blk_mq_queue(struct mapped_device *md)
+{
+ struct request_queue *q;
+ int err;
+
+ memset(&md->tag_set, 0, sizeof(md->tag_set));
+ md->tag_set.ops = &dm_mq_ops;
+ md->tag_set.queue_depth = BLKDEV_MAX_RQ;
+ md->tag_set.numa_node = NUMA_NO_NODE;
+ md->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
+ md->tag_set.nr_hw_queues = 1;
+ md->tag_set.cmd_size = sizeof(struct dm_rq_target_io);
+ md->tag_set.driver_data = md;
+
+ err = blk_mq_alloc_tag_set(&md->tag_set);
+ if (err)
+ return err;
+
+ q = blk_mq_init_allocated_queue(&md->tag_set, md->queue);
+ if (IS_ERR(q)) {
+ err = PTR_ERR(q);
+ goto out_tag_set;
+ }
+ md->queue = q;
+ dm_init_md_queue(md);
+
+ /* backfill 'mq' sysfs registration normally done in blk_register_queue */
+ blk_mq_register_disk(md->disk);
+
+ init_rq_based_worker_thread(md);
+
+ return 0;
+
+out_tag_set:
+ blk_mq_free_tag_set(&md->tag_set);
+ return err;
}
/*
@@ -2601,15 +2770,29 @@
*/
int dm_setup_md_queue(struct mapped_device *md)
{
- if (dm_md_type_request_based(md)) {
- if (!dm_init_request_based_queue(md)) {
+ int r;
+ unsigned md_type = dm_get_md_type(md);
+
+ switch (md_type) {
+ case DM_TYPE_REQUEST_BASED:
+ r = dm_init_request_based_queue(md);
+ if (r) {
DMWARN("Cannot initialize queue for request-based mapped device");
- return -EINVAL;
+ return r;
}
- } else {
- /* bio-based specific initialization */
+ break;
+ case DM_TYPE_MQ_REQUEST_BASED:
+ r = dm_init_request_based_blk_mq_queue(md);
+ if (r) {
+ DMWARN("Cannot initialize queue for request-based blk-mq mapped device");
+ return r;
+ }
+ break;
+ case DM_TYPE_BIO_BASED:
+ dm_init_old_md_queue(md);
blk_queue_make_request(md->queue, dm_make_request);
blk_queue_merge_bvec(md->queue, dm_merge_bvec);
+ break;
}
return 0;
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 889f3a5..eac8c36 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -267,9 +267,9 @@
#define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
#define DM_VERSION_MAJOR 4
-#define DM_VERSION_MINOR 30
+#define DM_VERSION_MINOR 31
#define DM_VERSION_PATCHLEVEL 0
-#define DM_VERSION_EXTRA "-ioctl (2014-12-22)"
+#define DM_VERSION_EXTRA "-ioctl (2015-3-12)"
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */
