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author | Mike Snitzer <snitzer@redhat.com> | 2018-01-09 06:01:13 +0300 |
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committer | Jens Axboe <axboe@kernel.dk> | 2018-01-15 18:41:38 +0300 |
commit | fa70d2e2c4a0a54ced98260c6a176cc94c876d27 (patch) | |
tree | 76c502acc8e87e03abc499aedd78150ce8703641 /block/blk-sysfs.c | |
parent | 667257e8b2988c0183ba23e2bcd6900e87961606 (diff) | |
download | linux-fa70d2e2c4a0a54ced98260c6a176cc94c876d27.tar.xz |
block: allow gendisk's request_queue registration to be deferred
Since I can remember DM has forced the block layer to allow the
allocation and initialization of the request_queue to be distinct
operations. Reason for this is block/genhd.c:add_disk() has requires
that the request_queue (and associated bdi) be tied to the gendisk
before add_disk() is called -- because add_disk() also deals with
exposing the request_queue via blk_register_queue().
DM's dynamic creation of arbitrary device types (and associated
request_queue types) requires the DM device's gendisk be available so
that DM table loads can establish a master/slave relationship with
subordinate devices that are referenced by loaded DM tables -- using
bd_link_disk_holder(). But until these DM tables, and their associated
subordinate devices, are known DM cannot know what type of request_queue
it needs -- nor what its queue_limits should be.
This chicken and egg scenario has created all manner of problems for DM
and, at times, the block layer.
Summary of changes:
- Add device_add_disk_no_queue_reg() and add_disk_no_queue_reg() variant
that drivers may use to add a disk without also calling
blk_register_queue(). Driver must call blk_register_queue() once its
request_queue is fully initialized.
- Return early from blk_unregister_queue() if QUEUE_FLAG_REGISTERED
is not set. It won't be set if driver used add_disk_no_queue_reg()
but driver encounters an error and must del_gendisk() before calling
blk_register_queue().
- Export blk_register_queue().
These changes allow DM to use add_disk_no_queue_reg() to anchor its
gendisk as the "master" for master/slave relationships DM must establish
with subordinate devices referenced in DM tables that get loaded. Once
all "slave" devices for a DM device are known its request_queue can be
properly initialized and then advertised via sysfs -- important
improvement being that no request_queue resource initialization
performed by blk_register_queue() is missed for DM devices anymore.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-sysfs.c')
-rw-r--r-- | block/blk-sysfs.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 9272452ff456..4a6a40ffd78e 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -921,6 +921,7 @@ unlock: mutex_unlock(&q->sysfs_lock); return ret; } +EXPORT_SYMBOL_GPL(blk_register_queue); void blk_unregister_queue(struct gendisk *disk) { @@ -929,6 +930,10 @@ void blk_unregister_queue(struct gendisk *disk) if (WARN_ON(!q)) return; + /* Return early if disk->queue was never registered. */ + if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags)) + return; + /* * Protect against the 'queue' kobj being accessed * while/after it is removed. |