fix: avoid error when zfs array is not configured

fix: include zfs arcstats in export list

Signed-off-by: Hudson Gerwing <grownuphudson@gmail.com>

Author: hewdoe

psutil/__init__.py

@@ -183,7 +183,7 @@
 
     # functions
     "pid_exists", "pids", "process_iter", "wait_procs",             # proc
-    "virtual_memory", "swap_memory",                                # memory
+    "virtual_memory", "swap_memory", "apply_zfs_arcstats",          # memory
     "cpu_times", "cpu_percent", "cpu_times_percent", "cpu_count",   # cpu
     "cpu_stats",  # "cpu_freq", "getloadavg"
     "net_io_counters", "net_connections", "net_if_addrs",           # network

psutil/_pslinux.py

@@ -608,20 +608,20 @@ def apply_zfs_arcstats(vm_stats: svmem):
     input virtual memory call results"""
     mems = {}
 
-    with open_binary('%s/spl/kstat/zfs/arcstats' % get_procfs_path()) as f:
-        for line in f:
-            fields = line.split()
-            try:
-                mems[fields[0]] = int(fields[2])
-            except ValueError:
-                # Not a key: value line
-                continue
-
     try:
+        with open_binary('%s/spl/kstat/zfs/arcstats' % get_procfs_path()) as f:
+            for line in f:
+                fields = line.split()
+                try:
+                    mems[fields[0]] = int(fields[2])
+                except ValueError:
+                    # Not a key: value line
+                    continue
+
         zfs_min = mems[b'c_min']
         zfs_size = mems[b'size']
-    except KeyError:
-        msg = ("ZFS ARC memory stats couldn't be determined, "
+    except (KeyError, FileNotFoundError):
+        msg = ("ZFS ARC memory is not configured on this device, "
                "no modification made to virtual memory stats")
         warnings.warn(msg, RuntimeWarning, stacklevel=2)
         zfs_min = zfs_size = 0