Commit 304f6808 authored by Alex Elder's avatar Alex Elder
Browse files

rbd: defer registering snapshot devices 



When a new snapshot is found in an rbd device's updated snapshot
context, __rbd_add_snap_dev() is called to create and insert an
entry in the rbd devices list of snapshots.  In addition, a Linux
device is registered to represent the snapshot.

For version 2 rbd images, it will be undesirable to initialize the
device right away.  So in anticipation of that, this patch separates
the insertion of a snapshot entry in the snaps list from the
creation of devices for those snapshots.

To do this, create a new function rbd_dev_snaps_register() which
traverses the list of snapshots and calls rbd_register_snap_dev()
on any that have not yet been registered.

Rename rbd_dev_snap_devs_update() to be rbd_dev_snaps_update()
to better reflect that only the entry in the snaps list and not
the snapshot's device is affected by the function.

For now, call rbd_dev_snaps_register() immediately after each
call to rbd_dev_snaps_update().

Signed-off-by: default avatarAlex Elder <elder@inktank.com>
Reviewed-by: default avatarJosh Durgin <josh.durgin@inktank.com>
parent 3fcf2581

drivers/block/rbd.c

+50 −10
Original line number Diff line number Diff line
@@ -204,7 +204,9 @@ static DEFINE_SPINLOCK(rbd_dev_list_lock); 
static LIST_HEAD(rbd_client_list);		/* clients */

static DEFINE_SPINLOCK(rbd_client_list_lock);



static int rbd_dev_snap_devs_update(struct rbd_device *rbd_dev);

static int rbd_dev_snaps_update(struct rbd_device *rbd_dev);

static int rbd_dev_snaps_register(struct rbd_device *rbd_dev);



static void rbd_dev_release(struct device *dev);

static ssize_t rbd_snap_add(struct device *dev,

			    struct device_attribute *attr,
@@ -1839,7 +1841,9 @@ static int __rbd_refresh_header(struct rbd_device *rbd_dev, u64 *hver) 
	WARN_ON(strcmp(rbd_dev->header.object_prefix, h.object_prefix));

	kfree(h.object_prefix);



	ret = rbd_dev_snap_devs_update(rbd_dev);

	ret = rbd_dev_snaps_update(rbd_dev);

	if (!ret)

		ret = rbd_dev_snaps_register(rbd_dev);



	up_write(&rbd_dev->header_rwsem);
@@ -2084,9 +2088,20 @@ static struct device_type rbd_snap_device_type = { 
	.release	= rbd_snap_dev_release,

};



static bool rbd_snap_registered(struct rbd_snap *snap)

{

	bool ret = snap->dev.type == &rbd_snap_device_type;

	bool reg = device_is_registered(&snap->dev);



	rbd_assert(!ret ^ reg);



	return ret;

}



static void __rbd_remove_snap_dev(struct rbd_snap *snap)

{

	list_del(&snap->node);

	if (device_is_registered(&snap->dev))

		device_unregister(&snap->dev);

}
@@ -2100,6 +2115,8 @@ static int rbd_register_snap_dev(struct rbd_snap *snap, 
	dev->parent = parent;

	dev->release = rbd_snap_dev_release;

	dev_set_name(dev, "snap_%s", snap->name);

	dout("%s: registering device for snapshot %s\n", __func__, snap->name);



	ret = device_register(dev);



	return ret;
@@ -2122,11 +2139,6 @@ static struct rbd_snap *__rbd_add_snap_dev(struct rbd_device *rbd_dev, 


	snap->size = rbd_dev->header.snap_sizes[i];

	snap->id = rbd_dev->header.snapc->snaps[i];

	if (device_is_registered(&rbd_dev->dev)) {

		ret = rbd_register_snap_dev(snap, &rbd_dev->dev);

		if (ret < 0)

			goto err;

	}



	return snap;
@@ -2149,7 +2161,7 @@ err: 
 * snapshot id, highest id first.  (Snapshots in the rbd_dev's list

 * are also maintained in that order.)

 */

static int rbd_dev_snap_devs_update(struct rbd_device *rbd_dev)

static int rbd_dev_snaps_update(struct rbd_device *rbd_dev)

{

	struct ceph_snap_context *snapc = rbd_dev->header.snapc;

	const u32 snap_count = snapc->num_snaps;
@@ -2236,6 +2248,31 @@ static int rbd_dev_snap_devs_update(struct rbd_device *rbd_dev) 
	return 0;

}



/*

 * Scan the list of snapshots and register the devices for any that

 * have not already been registered.

 */

static int rbd_dev_snaps_register(struct rbd_device *rbd_dev)

{

	struct rbd_snap *snap;

	int ret = 0;



	dout("%s called\n", __func__);

	if (!device_is_registered(&rbd_dev->dev))

		return 0;



	list_for_each_entry(snap, &rbd_dev->snaps, node) {

		if (!rbd_snap_registered(snap)) {

			ret = rbd_register_snap_dev(snap, &rbd_dev->dev);

			if (ret < 0)

				break;

		}

	}

	dout("%s: returning %d\n", __func__, ret);



	return ret;

}



static int rbd_bus_add_dev(struct rbd_device *rbd_dev)

{

	struct device *dev;
@@ -2585,7 +2622,10 @@ static ssize_t rbd_add(struct bus_type *bus, 
		goto err_out_bus;



	/* no need to lock here, as rbd_dev is not registered yet */

	rc = rbd_dev_snap_devs_update(rbd_dev);

	rc = rbd_dev_snaps_update(rbd_dev);

	if (rc)

		goto err_out_bus;

	rc = rbd_dev_snaps_register(rbd_dev);

	if (rc)

		goto err_out_bus;

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