rbd: don't hold ctl_mutex to get/put device
When an rbd device is first getting mapped, its device registration
is protected the control mutex. There is no need to do that though,
because the device has already been assigned an id that's guaranteed
to be unique.
An unmap of an rbd device won't proceed if the device has a non-zero
open count or is already being unmapped. So there's no need to hold
the control mutex in that case either.
Finally, an rbd device can't be opened if it is being removed, and
it won't go away if there is a non-zero open count. So here too
there's no need to hold the control mutex while getting or putting a
reference to an rbd device's Linux device structure.
Drop the mutex calls in these cases.
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 305c740..d735eb1 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -489,10 +489,8 @@
if (removing)
return -ENOENT;
- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
(void) get_device(&rbd_dev->dev);
set_device_ro(bdev, rbd_dev->mapping.read_only);
- mutex_unlock(&ctl_mutex);
return 0;
}
@@ -507,9 +505,7 @@
spin_unlock_irq(&rbd_dev->lock);
rbd_assert(open_count_before > 0);
- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
put_device(&rbd_dev->dev);
- mutex_unlock(&ctl_mutex);
}
static const struct block_device_operations rbd_bd_ops = {
@@ -4332,8 +4328,6 @@
struct device *dev;
int ret;
- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
-
dev = &rbd_dev->dev;
dev->bus = &rbd_bus_type;
dev->type = &rbd_device_type;
@@ -4342,8 +4336,6 @@
dev_set_name(dev, "%d", rbd_dev->dev_id);
ret = device_register(dev);
- mutex_unlock(&ctl_mutex);
-
return ret;
}
@@ -5149,8 +5141,6 @@
if (dev_id != ul)
return -EINVAL;
- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
-
ret = -ENOENT;
spin_lock(&rbd_dev_list_lock);
list_for_each(tmp, &rbd_dev_list) {
@@ -5171,7 +5161,7 @@
}
spin_unlock(&rbd_dev_list_lock);
if (ret < 0 || already)
- goto done;
+ return ret;
rbd_bus_del_dev(rbd_dev);
ret = rbd_dev_header_watch_sync(rbd_dev, false);
@@ -5179,11 +5169,8 @@
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);
- return ret;
+ return count;
}
/*