Commit 16f12266 authored by Mike Snitzer's avatar Mike Snitzer

dm: optimize dm_mq_queue_rq()

DM multipath is the only dm-mq target.  But that aside, request-based DM
only supports tables with a single target that is immutable.  Leverage
this fact in dm_mq_queue_rq() by using the 'immutable_target' stored in
the mapped_device when the table was made active.  This saves the need
to even take the read-side of the SRCU via dm_{get,put}_live_table.

If the active DM table does not have an immutable target (e.g. "error"
target was swapped in) then fallback to the slow-path where the target
is looked up from the live table.
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent f083b09b
......@@ -1684,7 +1684,8 @@ static int multipath_busy(struct dm_target *ti)
*---------------------------------------------------------------*/
static struct target_type multipath_target = {
.name = "multipath",
.version = {1, 10, 0},
.version = {1, 11, 0},
.features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
.module = THIS_MODULE,
.ctr = multipath_ctr,
.dtr = multipath_dtr,
......
......@@ -920,6 +920,16 @@ struct target_type *dm_table_get_immutable_target_type(struct dm_table *t)
return t->immutable_target_type;
}
struct dm_target *dm_table_get_immutable_target(struct dm_table *t)
{
/* Immutable target is implicitly a singleton */
if (t->num_targets > 1 ||
!dm_target_is_immutable(t->targets[0].type))
return NULL;
return t->targets;
}
struct dm_target *dm_table_get_wildcard_target(struct dm_table *t)
{
struct dm_target *uninitialized_var(ti);
......
......@@ -154,6 +154,7 @@ struct mapped_device {
/* Protect queue and type against concurrent access. */
struct mutex type_lock;
struct dm_target *immutable_target;
struct target_type *immutable_target_type;
struct gendisk *disk;
......@@ -2492,8 +2493,15 @@ 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))
if (dm_table_request_based(t)) {
stop_queue(q);
/*
* Leverage the fact that request-based DM targets are
* immutable singletons and establish md->immutable_target
* - used to optimize both dm_request_fn and dm_mq_queue_rq
*/
md->immutable_target = dm_table_get_immutable_target(t);
}
__bind_mempools(md, t);
......@@ -2564,7 +2572,6 @@ void dm_set_md_type(struct mapped_device *md, unsigned type)
unsigned dm_get_md_type(struct mapped_device *md)
{
BUG_ON(!mutex_is_locked(&md->type_lock));
return md->type;
}
......@@ -2641,28 +2648,15 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
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;
struct dm_target *ti = md->immutable_target;
/* 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);
if (unlikely(!ti)) {
int srcu_idx;
struct dm_table *map = dm_get_live_table(md, &srcu_idx);
ti = dm_table_find_target(map, pos);
if (!dm_target_is_valid(ti)) {
ti = dm_table_find_target(map, 0);
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;
......@@ -2678,8 +2672,10 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
*/
tio->ti = ti;
/* Clone the request if underlying devices aren't blk-mq */
if (dm_table_get_type(map) == DM_TYPE_REQUEST_BASED) {
/*
* Both the table and md type cannot change after initial table load
*/
if (dm_get_md_type(md) == DM_TYPE_REQUEST_BASED) {
/* clone request is allocated at the end of the pdu */
tio->clone = (void *)blk_mq_rq_to_pdu(rq) + sizeof(struct dm_rq_target_io);
(void) clone_rq(rq, md, tio, GFP_ATOMIC);
......
......@@ -73,6 +73,7 @@ int dm_table_resume_targets(struct dm_table *t);
int dm_table_any_congested(struct dm_table *t, int bdi_bits);
unsigned dm_table_get_type(struct dm_table *t);
struct target_type *dm_table_get_immutable_target_type(struct dm_table *t);
struct dm_target *dm_table_get_immutable_target(struct dm_table *t);
struct dm_target *dm_table_get_wildcard_target(struct dm_table *t);
bool dm_table_request_based(struct dm_table *t);
bool dm_table_mq_request_based(struct dm_table *t);
......
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