rbd: only set up watch for mapped images
Any changes to parent images are immaterial to any mapped clone.
So there is no need to have a watch event registered on header
objects except for the header object of an image that is mapped.
In fact, a watch request is a write operation, and we may only
have read access to a parent image.
We can't set up the watch request until we know the name of the
header object though. So pass a flag to rbd_dev_image_probe() to
indicate whether this probe is for a mapping or for a parent image.
Change the second parameter to rbd_dev_header_watch_sync() be
Boolean while we're at it.
This resolves:
http://tracker.ceph.com/issues/4941
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index dbfc44a..e417704 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -358,7 +358,7 @@
size_t count);
static ssize_t rbd_remove(struct bus_type *bus, const char *buf,
size_t count);
-static int rbd_dev_image_probe(struct rbd_device *rbd_dev);
+static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping);
static struct bus_attribute rbd_bus_attrs[] = {
__ATTR(add, S_IWUSR, NULL, rbd_add),
@@ -2664,7 +2664,7 @@
* Request sync osd watch/unwatch. The value of "start" determines
* whether a watch request is being initiated or torn down.
*/
-static int rbd_dev_header_watch_sync(struct rbd_device *rbd_dev, int start)
+static int rbd_dev_header_watch_sync(struct rbd_device *rbd_dev, bool start)
{
struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc;
struct rbd_obj_request *obj_request;
@@ -2698,7 +2698,7 @@
rbd_dev->watch_request->osd_req);
osd_req_op_watch_init(obj_request->osd_req, 0, CEPH_OSD_OP_WATCH,
- rbd_dev->watch_event->cookie, 0, start);
+ rbd_dev->watch_event->cookie, 0, start ? 1 : 0);
rbd_osd_req_format_write(obj_request);
ret = rbd_obj_request_submit(osdc, obj_request);
@@ -4549,7 +4549,7 @@
if (!parent)
goto out_err;
- ret = rbd_dev_image_probe(parent);
+ ret = rbd_dev_image_probe(parent, false);
if (ret < 0)
goto out_err;
rbd_dev->parent = parent;
@@ -4654,12 +4654,7 @@
static void rbd_dev_image_release(struct rbd_device *rbd_dev)
{
- int ret;
-
rbd_dev_unprobe(rbd_dev);
- ret = rbd_dev_header_watch_sync(rbd_dev, 0);
- if (ret)
- rbd_warn(rbd_dev, "failed to cancel watch event (%d)\n", ret);
kfree(rbd_dev->header_name);
rbd_dev->header_name = NULL;
rbd_dev->image_format = 0;
@@ -4671,9 +4666,11 @@
/*
* Probe for the existence of the header object for the given rbd
- * device.
+ * device. If this image is the one being mapped (i.e., not a
+ * parent), initiate a watch on its header object before using that
+ * object to get detailed information about the rbd image.
*/
-static int rbd_dev_image_probe(struct rbd_device *rbd_dev)
+static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
{
int ret;
int tmp;
@@ -4693,9 +4690,11 @@
if (ret)
goto err_out_format;
- ret = rbd_dev_header_watch_sync(rbd_dev, 1);
- if (ret)
- goto out_header_name;
+ if (mapping) {
+ ret = rbd_dev_header_watch_sync(rbd_dev, true);
+ if (ret)
+ goto out_header_name;
+ }
if (rbd_dev->image_format == 1)
ret = rbd_dev_v1_header_info(rbd_dev);
@@ -4719,9 +4718,12 @@
err_out_probe:
rbd_dev_unprobe(rbd_dev);
err_out_watch:
- tmp = rbd_dev_header_watch_sync(rbd_dev, 0);
- if (tmp)
- rbd_warn(rbd_dev, "unable to tear down watch request\n");
+ if (mapping) {
+ tmp = rbd_dev_header_watch_sync(rbd_dev, false);
+ if (tmp)
+ rbd_warn(rbd_dev, "unable to tear down "
+ "watch request (%d)\n", tmp);
+ }
out_header_name:
kfree(rbd_dev->header_name);
rbd_dev->header_name = NULL;
@@ -4788,7 +4790,7 @@
rbdc = NULL; /* rbd_dev now owns this */
spec = NULL; /* rbd_dev now owns this */
- rc = rbd_dev_image_probe(rbd_dev);
+ rc = rbd_dev_image_probe(rbd_dev, true);
if (rc < 0)
goto err_out_rbd_dev;
@@ -4910,10 +4912,13 @@
spin_unlock_irq(&rbd_dev->lock);
if (ret < 0)
goto done;
- ret = count;
rbd_bus_del_dev(rbd_dev);
+ ret = rbd_dev_header_watch_sync(rbd_dev, false);
+ if (ret)
+ rbd_warn(rbd_dev, "failed to cancel watch event (%d)\n", ret);
rbd_dev_image_release(rbd_dev);
module_put(THIS_MODULE);
+ ret = count;
done:
mutex_unlock(&ctl_mutex);