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: Alex Elder <elder@inktank.com> Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
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@ -204,7 +204,9 @@ static DEFINE_SPINLOCK(rbd_dev_list_lock);
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static LIST_HEAD(rbd_client_list); /* clients */
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static DEFINE_SPINLOCK(rbd_client_list_lock);
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static int rbd_dev_snap_devs_update(struct rbd_device *rbd_dev);
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static int rbd_dev_snaps_update(struct rbd_device *rbd_dev);
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static int rbd_dev_snaps_register(struct rbd_device *rbd_dev);
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static void rbd_dev_release(struct device *dev);
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static ssize_t rbd_snap_add(struct device *dev,
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struct device_attribute *attr,
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@ -1839,7 +1841,9 @@ static int __rbd_refresh_header(struct rbd_device *rbd_dev, u64 *hver)
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WARN_ON(strcmp(rbd_dev->header.object_prefix, h.object_prefix));
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kfree(h.object_prefix);
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ret = rbd_dev_snap_devs_update(rbd_dev);
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ret = rbd_dev_snaps_update(rbd_dev);
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if (!ret)
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ret = rbd_dev_snaps_register(rbd_dev);
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up_write(&rbd_dev->header_rwsem);
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@ -2084,10 +2088,21 @@ static struct device_type rbd_snap_device_type = {
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.release = rbd_snap_dev_release,
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};
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static bool rbd_snap_registered(struct rbd_snap *snap)
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{
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bool ret = snap->dev.type == &rbd_snap_device_type;
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bool reg = device_is_registered(&snap->dev);
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rbd_assert(!ret ^ reg);
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return ret;
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}
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static void __rbd_remove_snap_dev(struct rbd_snap *snap)
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{
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list_del(&snap->node);
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device_unregister(&snap->dev);
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if (device_is_registered(&snap->dev))
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device_unregister(&snap->dev);
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}
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static int rbd_register_snap_dev(struct rbd_snap *snap,
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@ -2100,6 +2115,8 @@ static int rbd_register_snap_dev(struct rbd_snap *snap,
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dev->parent = parent;
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dev->release = rbd_snap_dev_release;
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dev_set_name(dev, "snap_%s", snap->name);
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dout("%s: registering device for snapshot %s\n", __func__, snap->name);
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ret = device_register(dev);
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return ret;
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@ -2122,11 +2139,6 @@ static struct rbd_snap *__rbd_add_snap_dev(struct rbd_device *rbd_dev,
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snap->size = rbd_dev->header.snap_sizes[i];
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snap->id = rbd_dev->header.snapc->snaps[i];
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if (device_is_registered(&rbd_dev->dev)) {
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ret = rbd_register_snap_dev(snap, &rbd_dev->dev);
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if (ret < 0)
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goto err;
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}
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return snap;
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@ -2149,7 +2161,7 @@ err:
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* snapshot id, highest id first. (Snapshots in the rbd_dev's list
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* are also maintained in that order.)
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*/
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static int rbd_dev_snap_devs_update(struct rbd_device *rbd_dev)
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static int rbd_dev_snaps_update(struct rbd_device *rbd_dev)
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{
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struct ceph_snap_context *snapc = rbd_dev->header.snapc;
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const u32 snap_count = snapc->num_snaps;
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@ -2236,6 +2248,31 @@ static int rbd_dev_snap_devs_update(struct rbd_device *rbd_dev)
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return 0;
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}
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/*
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* Scan the list of snapshots and register the devices for any that
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* have not already been registered.
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*/
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static int rbd_dev_snaps_register(struct rbd_device *rbd_dev)
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{
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struct rbd_snap *snap;
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int ret = 0;
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dout("%s called\n", __func__);
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if (!device_is_registered(&rbd_dev->dev))
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return 0;
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list_for_each_entry(snap, &rbd_dev->snaps, node) {
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if (!rbd_snap_registered(snap)) {
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ret = rbd_register_snap_dev(snap, &rbd_dev->dev);
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if (ret < 0)
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break;
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}
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}
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dout("%s: returning %d\n", __func__, ret);
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return ret;
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}
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static int rbd_bus_add_dev(struct rbd_device *rbd_dev)
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{
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struct device *dev;
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@ -2585,7 +2622,10 @@ static ssize_t rbd_add(struct bus_type *bus,
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goto err_out_bus;
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/* no need to lock here, as rbd_dev is not registered yet */
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rc = rbd_dev_snap_devs_update(rbd_dev);
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rc = rbd_dev_snaps_update(rbd_dev);
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if (rc)
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goto err_out_bus;
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rc = rbd_dev_snaps_register(rbd_dev);
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if (rc)
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goto err_out_bus;
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