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>
(cherry picked from commit fa70d2e2c4
)
pull/10/head
parent
f00fb650dc
commit
a3edeedd61
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@ -924,6 +924,7 @@ unlock:
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mutex_unlock(&q->sysfs_lock);
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return ret;
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}
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EXPORT_SYMBOL_GPL(blk_register_queue);
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void blk_unregister_queue(struct gendisk *disk)
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{
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@ -932,6 +933,10 @@ void blk_unregister_queue(struct gendisk *disk)
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if (WARN_ON(!q))
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return;
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/* Return early if disk->queue was never registered. */
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if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
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return;
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/*
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* Protect against the 'queue' kobj being accessed
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* while/after it is removed.
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@ -641,16 +641,18 @@ exit:
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}
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/**
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* device_add_disk - add partitioning information to kernel list
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* __device_add_disk - add disk information to kernel list
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* @parent: parent device for the disk
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* @disk: per-device partitioning information
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* @register_queue: register the queue if set to true
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*
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* This function registers the partitioning information in @disk
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* with the kernel.
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*
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* FIXME: error handling
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*/
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void device_add_disk(struct device *parent, struct gendisk *disk)
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static void __device_add_disk(struct device *parent, struct gendisk *disk,
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bool register_queue)
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{
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dev_t devt;
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int retval;
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@ -691,7 +693,8 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
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exact_match, exact_lock, disk);
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}
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register_disk(parent, disk);
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blk_register_queue(disk);
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if (register_queue)
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blk_register_queue(disk);
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/*
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* Take an extra ref on queue which will be put on disk_release()
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@ -702,8 +705,19 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
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disk_add_events(disk);
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blk_integrity_add(disk);
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}
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void device_add_disk(struct device *parent, struct gendisk *disk)
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{
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__device_add_disk(parent, disk, true);
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}
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EXPORT_SYMBOL(device_add_disk);
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void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk)
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{
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__device_add_disk(parent, disk, false);
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}
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EXPORT_SYMBOL(device_add_disk_no_queue_reg);
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void del_gendisk(struct gendisk *disk)
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{
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struct disk_part_iter piter;
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@ -396,6 +396,11 @@ static inline void add_disk(struct gendisk *disk)
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{
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device_add_disk(NULL, disk);
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}
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extern void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk);
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static inline void add_disk_no_queue_reg(struct gendisk *disk)
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{
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device_add_disk_no_queue_reg(NULL, disk);
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}
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extern void del_gendisk(struct gendisk *gp);
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extern struct gendisk *get_gendisk(dev_t dev, int *partno);
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Loading…
Reference in New Issue