dm: fix incomplete request_queue initialization
DM is no longer prone to having its request_queue be improperly
initialized.
Summary of changes:
- defer DM's blk_register_queue() from add_disk()-time until
dm_setup_md_queue() by using add_disk_no_queue_reg() in alloc_dev().
- dm_setup_md_queue() is updated to fully initialize DM's request_queue
(_after_ all table loads have occurred and the request_queue's type,
features and limits are known).
A very welcome side-effect of these changes is DM no longer needs to:
1) backfill the "mq" sysfs entry (because historically DM didn't
initialize the request_queue to use blk-mq until _after_
blk_register_queue() was called via add_disk()).
2) call elv_register_queue() to get .request_fn request-based DM
device's "iosched" exposed in syfs.
In addition, blk-mq debugfs support is now made available because
request-based DM's blk-mq request_queue is now properly initialized
before dm_setup_md_queue() calls blk_register_queue().
These changes also stave off the need to introduce new DM-specific
workarounds in block core, e.g. this proposal:
https://patchwork.kernel.org/patch/10067961/
In the end DM devices should be less unicorn in nature (relative to
initialization and availability of block core infrastructure provided by
the request_queue).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Tested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7475739..8c26bfc 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1761,7 +1761,7 @@ static struct mapped_device *alloc_dev(int minor)
goto bad;
md->dax_dev = dax_dev;
- add_disk(md->disk);
+ add_disk_no_queue_reg(md->disk);
format_dev_t(md->name, MKDEV(_major, minor));
md->wq = alloc_workqueue("kdmflush", WQ_MEM_RECLAIM, 0);
@@ -2021,6 +2021,7 @@ EXPORT_SYMBOL_GPL(dm_get_queue_limits);
int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
{
int r;
+ struct queue_limits limits;
enum dm_queue_mode type = dm_get_md_type(md);
switch (type) {
@@ -2057,6 +2058,14 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
break;
}
+ r = dm_calculate_queue_limits(t, &limits);
+ if (r) {
+ DMERR("Cannot calculate initial queue limits");
+ return r;
+ }
+ dm_table_set_restrictions(t, md->queue, &limits);
+ blk_register_queue(md->disk);
+
return 0;
}