Isolate code specific to Linux in cmd/

Use sys.platform to choose the correct implementation of functions and
values of variables for the platform being run on.

Reword some comments to avoid describing implementation details in the
wrong places.

Reviewed-by: Kjeld Schouten <kjeld@schouten-lebbing.nl>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes #9561

cmd/Makefile.am

@@ -5,4 +5,6 @@ if USING_PYTHON
 SUBDIRS += arcstat arc_summary dbufstat
 endif
 
+if BUILD_LINUX
 SUBDIRS += mount_zfs zed zvol_id zvol_wait
+endif

cmd/arc_summary/arc_summary2

@@ -55,6 +55,30 @@ from subprocess import Popen, PIPE
 from decimal import Decimal as D
 
 
+if sys.platform.startswith('linux'):
+
+    def load_kstats(namespace):
+        """Collect information on a specific subsystem of the ARC"""
+
+        kstat = 'kstat.zfs.misc.%s.%%s' % namespace
+        path = '/proc/spl/kstat/zfs/%s' % namespace
+        with open(path) as f:
+            entries = [line.strip().split() for line in f][2:] # Skip header
+        return [(kstat % name, D(value)) for name, _, value in entries]
+
+    def load_tunables():
+        basepath = '/sys/module/zfs/parameters'
+        tunables = {}
+        for name in os.listdir(basepath):
+            if not name:
+                continue
+            path = '%s/%s' % (basepath, name)
+            with open(path) as f:
+                value = f.read()
+            tunables[name] = value.strip()
+        return tunables
+
+
 show_tunable_descriptions = False
 alternate_tunable_layout = False
 
@@ -77,15 +101,6 @@ def get_Kstat():
     of the same name.
     """
 
-    def load_kstats(namespace):
-        """Collect information on a specific subsystem of the ARC"""
-
-        kstat = 'kstat.zfs.misc.%s.%%s' % namespace
-        path = '/proc/spl/kstat/zfs/%s' % namespace
-        with open(path) as f:
-            entries = [line.strip().split() for line in f][2:] # Skip header
-        return [(kstat % name, D(value)) for name, _, value in entries]
-
     Kstat = {}
     Kstat.update(load_kstats('arcstats'))
     Kstat.update(load_kstats('zfetchstats'))
@@ -917,18 +932,6 @@ def _tunable_summary(Kstat):
     global show_tunable_descriptions
     global alternate_tunable_layout
 
-    def load_tunables():
-        basepath = '/sys/module/zfs/parameters'
-        tunables = {}
-        for name in os.listdir(basepath):
-            if not name:
-                continue
-            path = '%s/%s' % (basepath, name)
-            with open(path) as f:
-                value = f.read()
-            tunables[name] = value.strip()
-        return tunables
-
     tunables = load_tunables()
     descriptions = {}
 

cmd/arc_summary/arc_summary3

@@ -46,9 +46,6 @@ import time
 DESCRIPTION = 'Print ARC and other statistics for ZFS on Linux'
 INDENT = ' '*8
 LINE_LENGTH = 72
-PROC_PATH = '/proc/spl/kstat/zfs/'
-SPL_PATH = '/sys/module/spl/parameters/'
-TUNABLES_PATH = '/sys/module/zfs/parameters/'
 DATE_FORMAT = '%a %b %d %H:%M:%S %Y'
 TITLE = 'ZFS Subsystem Report'
 
@@ -83,6 +80,17 @@ parser.add_argument('-s', '--section', dest='section', help=SECTION_HELP)
 ARGS = parser.parse_args()
 
 
+if sys.platform.startswith('linux'):
+    KSTAT_PATH = '/proc/spl/kstat/zfs/'
+    SPL_PATH = '/sys/module/spl/parameters/'
+    TUNABLES_PATH = '/sys/module/zfs/parameters/'
+    VDEV_CACHE_SIZE = 'zfs_vdev_cache_size'
+
+    def load_kstats(section):
+        path = os.path.join(KSTAT_PATH, section)
+        with open(path) as f:
+            return list(f)[2:] # Get rid of header
+
     def get_params(basepath):
         """Collect information on the Solaris Porting Layer (SPL) or the
         tunables, depending on the PATH given. Does not check if PATH is
@@ -96,19 +104,15 @@ def get_params(basepath):
                 result[name] = value.strip()
         return result
 
-
     def get_spl_params():
         return get_params(SPL_PATH)
 
-
     def get_tunable_params():
         return get_params(TUNABLES_PATH)
 
-
     def get_vdev_params():
         return get_params(TUNABLES_PATH)
 
-
     def get_version_impl(request):
         # The original arc_summary called /sbin/modinfo/{spl,zfs} to get
         # the version information. We switch to /sys/module/{spl,zfs}/version
@@ -119,7 +123,6 @@ def get_version_impl(request):
         # The recommended way to do this is with subprocess.run(). However,
         # some installed versions of Python are < 3.5, so we offer them
         # the option of doing it the old way (for now)
-    info = ''
         if 'run' in dir(subprocess):
             info = subprocess.run(command, stdout=subprocess.PIPE,
                                   universal_newlines=True)
@@ -131,12 +134,6 @@ def get_version_impl(request):
         return version
 
 
-def load_kstats(section):
-    path = os.path.join(PROC_PATH, section)
-    with open(path) as f:
-        return list(f)[2:] # Get rid of header
-
-
 def cleanup_line(single_line):
     """Format a raw line of data from /proc and isolate the name value
     part, returning a tuple with each. Currently, this gets rid of the
@@ -299,10 +296,10 @@ def format_raw_line(name, value):
 
 
 def get_kstats():
-    """Collect information on the ZFS subsystem from the /proc Linux virtual
-    file system. The step does not perform any further processing, giving us
-    the option to only work on what is actually needed. The name "kstat" is a
-    holdover from the Solaris utility of the same name.
+    """Collect information on the ZFS subsystem. The step does not perform any
+    further processing, giving us the option to only work on what is actually
+    needed. The name "kstat" is a holdover from the Solaris utility of the same
+    name.
     """
 
     result = {}
@@ -382,7 +379,7 @@ def get_version(request):
 
 def print_header():
     """Print the initial heading with date and time as well as info on the
-    Linux and ZFS versions. This is not called for the graph.
+    kernel and ZFS versions. This is not called for the graph.
     """
 
     # datetime is now recommended over time but we keep the exact formatting
@@ -779,7 +776,7 @@ def section_vdev(kstats_dict):
     # for details
     tunables = get_vdev_params()
 
-    if tunables['zfs_vdev_cache_size'] == '0':
+    if tunables[VDEV_CACHE_SIZE] == '0':
         print('VDEV cache disabled, skipping section\n')
         return
 

cmd/arcstat/arcstat

@@ -54,6 +54,7 @@ import copy
 from decimal import Decimal
 from signal import signal, SIGINT, SIGWINCH, SIG_DFL
 
+
 cols = {
     # HDR:        [Size, Scale, Description]
     "time":       [8, -1, "Time"],
@@ -118,6 +119,26 @@ out = None
 kstat = None
 
 
+if sys.platform.startswith('linux'):
+    def kstat_update():
+        global kstat
+
+        k = [line.strip() for line in open('/proc/spl/kstat/zfs/arcstats')]
+
+        if not k:
+            sys.exit(1)
+
+        del k[0:2]
+        kstat = {}
+
+        for s in k:
+            if not s:
+                continue
+
+            name, unused, value = s.split()
+            kstat[name] = Decimal(value)
+
+
 def detailed_usage():
     sys.stderr.write("%s\n" % cmd)
     sys.stderr.write("Field definitions are as follows:\n")
@@ -148,25 +169,6 @@ def usage():
     sys.exit(1)
 
 
-def kstat_update():
-    global kstat
-
-    k = [line.strip() for line in open('/proc/spl/kstat/zfs/arcstats')]
-
-    if not k:
-        sys.exit(1)
-
-    del k[0:2]
-    kstat = {}
-
-    for s in k:
-        if not s:
-            continue
-
-        name, unused, value = s.split()
-        kstat[name] = Decimal(value)
-
-
 def snap_stats():
     global cur
     global kstat