dm: remove support for stacking dm-mq on .request_fn device(s)
Remove all fiddley code that propped up this support for a blk-mq
request-queue ontop of all .request_fn devices.
Testing has proven this niche request-based dm-mq mode to be buggy, when
testing fault tolerance with DM multipath, and there is no point trying
to preserve it.
Should help improve efficiency of pure dm-mq code and make code
maintenance less delicate.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 8a62e43..26fedd9 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1141,11 +1141,6 @@
else if (!md->queue->mq_ops)
/* request_fn queue stacked on request_fn queue(s) */
free_clone_request(md, clone);
- /*
- * NOTE: for the blk-mq queue stacked on request_fn queue(s) case:
- * no need to call free_clone_request() because we leverage blk-mq by
- * allocating the clone at the end of the blk-mq pdu (see: clone_rq)
- */
if (!md->queue->mq_ops)
free_rq_tio(tio);
@@ -1866,24 +1861,18 @@
struct dm_rq_target_io *tio, gfp_t gfp_mask)
{
/*
- * Do not allocate a clone if tio->clone was already set
- * (see: dm_mq_queue_rq).
+ * Create clone for use with .request_fn request_queue
*/
- bool alloc_clone = !tio->clone;
struct request *clone;
- if (alloc_clone) {
- clone = alloc_clone_request(md, gfp_mask);
- if (!clone)
- return NULL;
- } else
- clone = tio->clone;
+ clone = alloc_clone_request(md, gfp_mask);
+ if (!clone)
+ return NULL;
blk_rq_init(NULL, clone);
if (setup_clone(clone, rq, tio, gfp_mask)) {
/* -ENOMEM */
- if (alloc_clone)
- free_clone_request(md, clone);
+ free_clone_request(md, clone);
return NULL;
}
@@ -2692,22 +2681,12 @@
*/
tio->ti = ti;
- /*
- * 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);
- queue_kthread_work(&md->kworker, &tio->work);
- } else {
- /* Direct call is fine since .queue_rq allows allocations */
- if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE) {
- /* Undo dm_start_request() before requeuing */
- rq_end_stats(md, rq);
- rq_completed(md, rq_data_dir(rq), false);
- return BLK_MQ_RQ_QUEUE_BUSY;
- }
+ /* Direct call is fine since .queue_rq allows allocations */
+ if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE) {
+ /* Undo dm_start_request() before requeuing */
+ rq_end_stats(md, rq);
+ rq_completed(md, rq_data_dir(rq), false);
+ return BLK_MQ_RQ_QUEUE_BUSY;
}
return BLK_MQ_RQ_QUEUE_OK;
@@ -2726,6 +2705,11 @@
struct request_queue *q;
int err;
+ if (dm_get_md_type(md) == DM_TYPE_REQUEST_BASED) {
+ DMERR("request-based dm-mq may only be stacked on blk-mq device(s)");
+ return -EINVAL;
+ }
+
md->tag_set = kzalloc(sizeof(struct blk_mq_tag_set), GFP_KERNEL);
if (!md->tag_set)
return -ENOMEM;
@@ -2738,10 +2722,6 @@
md->tag_set->driver_data = md;
md->tag_set->cmd_size = sizeof(struct dm_rq_target_io);
- if (md_type == DM_TYPE_REQUEST_BASED) {
- /* put the memory for non-blk-mq clone at the end of the pdu */
- md->tag_set->cmd_size += sizeof(struct request);
- }
err = blk_mq_alloc_tag_set(md->tag_set);
if (err)
@@ -2758,9 +2738,6 @@
/* backfill 'mq' sysfs registration normally done in blk_register_queue */
blk_mq_register_disk(md->disk);
- if (md_type == DM_TYPE_REQUEST_BASED)
- init_rq_based_worker_thread(md);
-
return 0;
out_tag_set: