tests: monitor /dev for new nvme block device

The attach operation takes a bit of time and is asynchronous, thus we
should monitor if the block device appears for a period, before
returning an error.

Signed-off-by: Daniel Wagner <wagi@kernel.org>

Author: igaw

tests/nvme_test.py

@@ -31,10 +31,21 @@
 import subprocess
 import sys
 import unittest
+import pyinotify
 
 from nvme_test_logger import TestNVMeLogger
 
 
+class EventHandler(pyinotify.ProcessEvent):
+    def __init__(self, target_file):
+        self.target_file = target_file
+        self.file_created = False
+
+    def process_IN_CREATE(self, event):
+        if event.pathname == self.target_file:
+            self.file_created = True
+
+
 class TestNVMe(unittest.TestCase):
 
     """
@@ -407,12 +418,31 @@ def attach_ns(self, ctrl_id, nsid):
         err = subprocess.call(attach_ns_cmd,
                               shell=True,
                               stdout=subprocess.DEVNULL)
-        if err == 0:
-            # enumerate new namespace block device
-            self.nvme_reset_ctrl()
-            # check if new namespace block device exists
-            err = 0 if stat.S_ISBLK(os.stat(self.ctrl + "n"  + str(nsid)).st_mode) else 1
-        return err
+        if err != 0:
+            return err
+
+        device_path = f"{self.ctrl}n{str(nsid)}"
+        watch_dir = os.path.dirname(device_path)
+
+        wm = pyinotify.WatchManager()
+        handler = EventHandler(device_path)
+        notifier = pyinotify.Notifier(wm, handler)
+        wm.add_watch(watch_dir, pyinotify.IN_CREATE)
+
+        if os.path.exists(device_path) and stat.S_ISBLK(os.stat(device_path).st_mode):
+            return 0
+
+        start_time = time.time()
+        timeout = 5  # seconds
+
+        while time.time() - start_time < timeout:
+            notifier.process_events()
+            if handler.file_created and stat.S_ISBLK(os.stat(device_path).st_mode):
+                return 0
+            if notifier.check_events(timeout=500):  # milli seconds
+                notifier.read_events()
+
+        return 1
 
     def detach_ns(self, ctrl_id, nsid):
         """ Wrapper for detaching the namespace.