Currently if dm_mod.use_blk_mq=Y (or a DM-multipath table is loaded with
queue_mode=mq) and all underlying devices are not blk-mq, DM core will
fail with the error:
"table load rejected: all devices are not blk-mq request-stackable"
This all-blk-mq-or-nothing approach is too cut-throat because it
prevents access to data stored on what could have been a previously
working multipath setup (e.g. if user decides to try dm_mod.use_blk_mq=Y
or queue_mode=mq only to find their underlying devices aren't blk-mq).
This restriction, and others like not being able to stack a top-level
blk-mq request-queue ontop of old .request_fn device(s), can be removed
thanks to commit eb8db831be ("dm: always defer request allocation to the
owner of the request_queue").
Now that request-based DM will always rely on the target (multipath) to
call blk_get_request() to create a clone request it is possible to
support all 4 permutations of stacking old .request_fn and blk-mq
request_queues.
Depends-on: eb8db831be ("dm: always defer request allocation to the owner of
the request_queue")
Reported-by: Ewan Milne <emi...@redhat.com>
Signed-off-by: Mike Snitzer <snit...@redhat.com>
---
drivers/md/dm-rq.c | 5 -----
drivers/md/dm-table.c | 31 +++----------------------------
drivers/md/dm.h | 1 -
3 files changed, 3 insertions(+), 34 deletions(-)
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 95bb44c..d64677b 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -782,11 +782,6 @@ int dm_mq_init_request_queue(struct mapped_device *md,
struct dm_table *t)
struct dm_target *immutable_tgt;
int err;
- if (!dm_table_all_blk_mq_devices(t)) {
- DMERR("request-based dm-mq may only be stacked on blk-mq
device(s)");
- return -EINVAL;
- }
-
md->tag_set = kzalloc_node(sizeof(struct blk_mq_tag_set), GFP_KERNEL,
md->numa_node_id);
if (!md->tag_set)
return -ENOMEM;
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index a39bcd9..e630768 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -46,7 +46,6 @@ struct dm_table {
bool integrity_supported:1;
bool singleton:1;
- bool all_blk_mq:1;
unsigned integrity_added:1;
/*
@@ -910,7 +909,6 @@ static int dm_table_determine_type(struct dm_table *t)
{
unsigned i;
unsigned bio_based = 0, request_based = 0, hybrid = 0;
- unsigned sq_count = 0, mq_count = 0;
struct dm_target *tgt;
struct dm_dev_internal *dd;
struct list_head *devices = dm_table_get_devices(t);
@@ -985,11 +983,9 @@ static int dm_table_determine_type(struct dm_table *t)
int srcu_idx;
struct dm_table *live_table = dm_get_live_table(t->md,
&srcu_idx);
- /* inherit live table's type and all_blk_mq */
- if (live_table) {
+ /* inherit live table's type */
+ if (live_table)
t->type = live_table->type;
- t->all_blk_mq = live_table->all_blk_mq;
- }
dm_put_live_table(t->md, srcu_idx);
return 0;
}
@@ -999,25 +995,9 @@ static int dm_table_determine_type(struct dm_table *t)
struct request_queue *q = bdev_get_queue(dd->dm_dev->bdev);
if (!blk_queue_stackable(q)) {
- DMERR("table load rejected: including"
- " non-request-stackable devices");
+ DMERR("table load rejected: includes
non-request-stackable devices");
return -EINVAL;
}
-
- if (q->mq_ops)
- mq_count++;
- else
- sq_count++;
- }
- if (sq_count && mq_count) {
- DMERR("table load rejected: not all devices are blk-mq
request-stackable");
- return -EINVAL;
- }
- t->all_blk_mq = mq_count > 0;
-
- if (t->type == DM_TYPE_MQ_REQUEST_BASED && !t->all_blk_mq) {
- DMERR("table load rejected: all devices are not blk-mq
request-stackable");
- return -EINVAL;
}
return 0;
@@ -1067,11 +1047,6 @@ bool dm_table_request_based(struct dm_table *t)
return __table_type_request_based(dm_table_get_type(t));
}
-bool dm_table_all_blk_mq_devices(struct dm_table *t)
-{
- return t->all_blk_mq;
-}
-
static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device
*md)
{
enum dm_queue_mode type = dm_table_get_type(t);
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 38c84c0..c484c4d 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -70,7 +70,6 @@ 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_bio_based(struct dm_table *t);
bool dm_table_request_based(struct dm_table *t);
-bool dm_table_all_blk_mq_devices(struct dm_table *t);
void dm_table_free_md_mempools(struct dm_table *t);
struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
--
2.10.1
