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dm: add full blk-mq support to request-based DM

Browse source 
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>
This commit is contained in:
Mike Snitzer 2015-03-08 00:51:47 -05:00
parent 0ce65797a7
commit bfebd1cdb4
4 changed files with 261 additions and 73 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
drivers/md/dm-mpath.c
View file

@ -1703,7 +1703,7 @@ out:
*---------------------------------------------------------------*/
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,

11
drivers/md/dm-table.c
View file

@ -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 @@ void dm_table_run_md_queue_async(struct dm_table *t)
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);

317
drivers/md/dm.c
View file

@ -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 @@ struct mapped_device {
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 @@ static void end_clone_bio(struct bio *clone, int error)
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 @@ static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
* 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 rq_completed(struct mapped_device *md, int rw, bool run_queue)
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 @@ static void dm_end_request(struct request *clone, int error)
}
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 @@ static void dm_unprep_request(struct request *rq)
/*
* 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 @@ static void dm_requeue_unmapped_request(struct request *clone)
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_done(struct request *clone, int error, bool mapped)
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_softirq_done(struct request *rq)
*/
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 @@ static void dm_kill_unmapped_request(struct request *rq, int error)
}
/*
* 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 struct request *clone_rq(struct request *rq, struct mapped_device *md,
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 @@ static struct dm_rq_target_io *prep_tio(struct request *rq,
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 @@ static int dm_prep_fn(struct request_queue *q, struct request *rq)
* 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 @@ static int map_request(struct dm_target *ti, struct request *rq,
}
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 @@ static void map_tio_request(struct kthread_work *work)
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 @@ static void dm_request_fn(struct request_queue *q)
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 @@ static void dm_init_md_queue(struct mapped_device *md)
{
/*
* 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 @@ static void dm_init_md_queue(struct mapped_device *md)
* 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 unlock_fs(struct mapped_device *md);
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 @@ static void free_dev(struct mapped_device *md)
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 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
* 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 @@ unsigned dm_get_md_type(struct mapped_device *md)
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 @@ struct queue_limits *dm_get_queue_limits(struct mapped_device *md)
}
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 @@ static int dm_init_request_based_queue(struct mapped_device *md)
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 @@ static int dm_init_request_based_queue(struct mapped_device *md)
*/
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;

4
include/uapi/linux/dm-ioctl.h
View file

@ -267,9 +267,9 @@ enum {
#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 */