Description of problem:

Under heavy load (creating and deleting many devices simultaneously) multipath calls (for example "multipath -l $device") will fail if during discovery phase there's a problem retrieving individual udev information from a device (because it has been deleted after listing the devices).  And the call should not fail.

In the code we get the list of devices [A], then if we fail at [B], we will end up returning a positive number at [C] and then caller will fail operation.


        udev_enumerate_add_match_subsystem(udev_iter, "block");
        udev_enumerate_scan_devices(udev_iter);   <-------------------------------- A
        udev_list_entry_foreach(entry,
                                udev_enumerate_get_list_entry(udev_iter)) {
                const char *devtype;
                devpath = udev_list_entry_get_name(entry);
                condlog(4, "Discover device %s", devpath);
                udevice = udev_device_new_from_syspath(conf->udev, devpath); <----- B
                if (!udevice) {
                        condlog(4, "%s: no udev information", devpath);
                        r++;
                        continue;
                }
                devtype = udev_device_get_devtype(udevice);
                if(devtype && !strncmp(devtype, "disk", 4))
                        r += path_discover(pathvec, conf, udevice, flag);
                udev_device_unref(udevice);
        }

        condlog(4, "Discovery status %d", r);
        return r;   <-------------------------------------------------------------- C
    }

I believe upstream commit 646e754853b123a075b4cede7d9ccf540e8c9b0c should fix this.