rbd-nbd: fix unused nbd device search bug in container

In some container scenarios, the host may choose to map a specific nbd device, for example, /dev/nbd6 into the container, in that case, the nbd device available in the container is not numbered from 0. The current unused nbd device search function will return no result. This patch fixes it. Fixes: http://tracker.ceph.com/issues/22012 Signed-off-by: Li Wang <[email protected]> Reviewed-by: Yunchuan Wen <[email protected]>
zmc · Nov 3, 2017 · be0f958 · be0f958
1 parent 07d5b81
commit be0f958
Showing 1 changed file with 15 additions and 0 deletions.
diff --git a/src/tools/rbd_nbd/rbd-nbd.cc b/src/tools/rbd_nbd/rbd-nbd.cc
@@ -605,12 +605,27 @@ static int do_map(int argc, const char *argv[], Config *cfg)
   if (cfg->devpath.empty()) {
     char dev[64];
     bool try_load_module = true;
+    const char *path = "/sys/module/nbd/parameters/nbds_max";
+    int nbds_max = -1;
+    if (access(path, F_OK) == 0) {
+      std::ifstream ifs;
+      ifs.open(path, std::ifstream::in);
+      if (ifs.is_open()) {
+        ifs >> nbds_max;
+        ifs.close();
+      }
+    }
+
     while (true) {
       snprintf(dev, sizeof(dev), "/dev/nbd%d", index);
 
       nbd = open_device(dev, cfg, try_load_module);
       try_load_module = false;
       if (nbd < 0) {
+        if (nbd == -EPERM && nbds_max != -1 && index < (nbds_max-1)) {
+          ++index;
+          continue;
+        }
         r = nbd;
         cerr << "rbd-nbd: failed to find unused device" << std::endl;
         goto close_fd;