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authorMike Snitzer <snitzer@redhat.com>2018-01-09 06:01:13 +0300
committerJens Axboe <axboe@kernel.dk>2018-01-15 18:41:38 +0300
commitfa70d2e2c4a0a54ced98260c6a176cc94c876d27 (patch)
tree76c502acc8e87e03abc499aedd78150ce8703641 /include/linux/genhd.h
parent667257e8b2988c0183ba23e2bcd6900e87961606 (diff)
downloadlinux-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 'include/linux/genhd.h')
-rw-r--r--include/linux/genhd.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 5144ebe046c9..5e3531027b51 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -395,6 +395,11 @@ static inline void add_disk(struct gendisk *disk)
{
device_add_disk(NULL, disk);
}
+extern void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk);
+static inline void add_disk_no_queue_reg(struct gendisk *disk)
+{
+ device_add_disk_no_queue_reg(NULL, disk);
+}
extern void del_gendisk(struct gendisk *gp);
extern struct gendisk *get_gendisk(dev_t dev, int *partno);