From fa70d2e2c4a0a54ced98260c6a176cc94c876d27 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Mon, 8 Jan 2018 22:01:13 -0500 Subject: [PATCH] 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 Reviewed-by: Ming Lei Signed-off-by: Jens Axboe --- block/blk-sysfs.c | 5 +++++ block/genhd.c | 20 +++++++++++++++++--- include/linux/genhd.h | 5 +++++ 3 files changed, 27 insertions(+), 3 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 @@ int blk_register_queue(struct gendisk *disk) 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. diff --git a/block/genhd.c b/block/genhd.c index 00620e01e043..88a53c188cb7 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -629,16 +629,18 @@ static void register_disk(struct device *parent, struct gendisk *disk) } /** - * device_add_disk - add partitioning information to kernel list + * __device_add_disk - add disk information to kernel list * @parent: parent device for the disk * @disk: per-device partitioning information + * @register_queue: register the queue if set to true * * This function registers the partitioning information in @disk * with the kernel. * * FIXME: error handling */ -void device_add_disk(struct device *parent, struct gendisk *disk) +static void __device_add_disk(struct device *parent, struct gendisk *disk, + bool register_queue) { dev_t devt; int retval; @@ -682,7 +684,8 @@ void device_add_disk(struct device *parent, struct gendisk *disk) exact_match, exact_lock, disk); } register_disk(parent, disk); - blk_register_queue(disk); + if (register_queue) + blk_register_queue(disk); /* * Take an extra ref on queue which will be put on disk_release() @@ -693,8 +696,19 @@ void device_add_disk(struct device *parent, struct gendisk *disk) disk_add_events(disk); blk_integrity_add(disk); } + +void device_add_disk(struct device *parent, struct gendisk *disk) +{ + __device_add_disk(parent, disk, true); +} EXPORT_SYMBOL(device_add_disk); +void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk) +{ + __device_add_disk(parent, disk, false); +} +EXPORT_SYMBOL(device_add_disk_no_queue_reg); + void del_gendisk(struct gendisk *disk) { struct disk_part_iter piter; 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);