Commit c100ec49 authored by Mike Snitzer's avatar Mike Snitzer Committed by Jens Axboe

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: default avatarMike Snitzer <snitzer@redhat.com>
Tested-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 69e0927b
......@@ -713,8 +713,6 @@ int dm_old_init_request_queue(struct mapped_device *md, struct dm_table *t)
return error;
}
elv_register_queue(md->queue);
return 0;
}
......@@ -812,15 +810,8 @@ int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t)
}
dm_init_md_queue(md);
/* backfill 'mq' sysfs registration normally done in blk_register_queue */
err = blk_mq_register_dev(disk_to_dev(md->disk), q);
if (err)
goto out_cleanup_queue;
return 0;
out_cleanup_queue:
blk_cleanup_queue(q);
out_tag_set:
blk_mq_free_tag_set(md->tag_set);
out_kfree_tag_set:
......
......@@ -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;
}
......
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