Hi David, Thanks for comments, more below..
On 05/27/2015 07:34 PM, David Sterba wrote:
On Fri, May 22, 2015 at 11:33:48PM +0800, Anand Jain wrote:
+void btrfs_free_stale_device(struct btrfs_device *cur_dev)
+{
+ int del = 0;
+ struct btrfs_fs_devices *fs_devs;
+ struct btrfs_device *dev;
+
+ if (!rcu_str_deref(cur_dev->name))
+ return;
This looks like rcu-unprotected access, though there's an outer mutext
held in device_list_add that calls btrfs_free_stale_device. I'm not sure
that the device name should be used to do any sorts of checks at all.
you are right. I got this corrected in v5.2 just sent out.
+ list_for_each_entry(fs_devs, &fs_uuids, list) {
+ if (fs_devs->opened)
+ continue;
+ if (fs_devs->seeding)
+ continue;
+ list_for_each_entry(dev, &fs_devs->devices, dev_list) {
+ if (dev == cur_dev)
+ continue;
+
+ /*
+ * Todo: This won't be enough. What if same device
+ * comes back with new uuid and with its mapper path?
+ * But for now, this does helps as mostly an admin will
+ * use either mapper or non mapper path throughout.
+ */
+ if (!rcu_str_deref(dev->name))
+ continue;
+ if (!strcmp(rcu_str_deref(dev->name),
+ rcu_str_deref(cur_dev->name))) {
+ del = 1;
+ break;
+ }
+ }
+ if (del) {
+ /* delete the stale */
+ if (fs_devs->num_devices == 1) {
+ btrfs_sysfs_remove_fsid(fs_devs);
+ list_del(&fs_devs->list);
+ free_fs_devices(fs_devs);
+ } else {
+ fs_devs->num_devices--;
+ list_del(&dev->dev_list);
+ rcu_string_free(dev->name);
+ kfree(dev);
Devices are normally freed by the rcu through free_device, this looks
suspicious to mix both approaches.
yes its bit of mixed up, also in other parts as well, for eg:
free_fs_devices(). Here I am following free_fs_devices,
since free_stale will check on the devices that are unmounted.
+ }
+ break;
+ }
+ }
+ return;
Unnecessary return
right.
+}
+
/*
* Add new device to list of registered devices
*
@@ -560,6 +609,8 @@ static noinline int device_list_add(const char *path,
if (!fs_devices->opened)
device->generation = found_transid;
+ btrfs_free_stale_device(device);
It might be safe to do that in the end, but it should be explained
somewhere.
Added, Thanks, Anand
+
*fs_devices_ret = fs_devices;
return ret;
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