Merge pull request #89 from mikechristie/alua-exception

Fix crash during restore due to ALUA exception

rtslib/__init__.py

@@ -23,6 +23,7 @@
 
 from .root import RTSRoot
 from .utils import RTSLibError, RTSLibBrokenLink, RTSLibNotInCFS
+from .utils import RTSLibALUANotSupported
 
 from .target import LUN, MappedLUN
 from .target import NodeACL, NetworkPortal, TPG, Target

rtslib/alua.py

@@ -18,7 +18,7 @@
 '''
 
 from .node import CFSNode
-from .utils import RTSLibError, fread, fwrite
+from .utils import RTSLibError, RTSLibALUANotSupported, fread, fwrite
 
 alua_rw_params = ['alua_access_state', 'alua_access_status',
                   'alua_write_metadata', 'alua_access_type', 'preferred',
@@ -46,6 +46,12 @@ def __init__(self, storage_object, name, tag=None):
         @param tag: target port group id. If not passed in, try to look
                     up existing ALUA TPG with the same name
         """
+        # kernel partially sets up default_tg_pt_gp and will let you partially
+        # setup ALUA groups for pscsi and user, but writing to some of the
+        # files will crash the kernel. Just fail to even create groups until
+        # the kernel is fixed.
+        if storage_object.alua_supported is False:
+            raise RTSLibALUANotSupported("Backend does not support ALUA setup")
 
         # default_tg_pt_gp takes tag 1
         if tag is not None and (tag > 65535 or tag < 1):

rtslib/root.py

@@ -26,7 +26,7 @@
 from .target import Target
 from .fabric import FabricModule
 from .tcm import so_mapping, StorageObject
-from .utils import RTSLibError, modprobe, mount_configfs
+from .utils import RTSLibError, RTSLibALUANotSupported, modprobe, mount_configfs
 from .utils import dict_remove, set_attributes
 from .alua import ALUATargetPortGroup
 
@@ -224,7 +224,10 @@ def so_err_func(x):
             set_attributes(so_obj, so.get('attributes', {}), so_err_func)
 
             for alua_tpg in so.get('alua_tpgs', {}):
-                ALUATargetPortGroup.setup(so_obj, alua_tpg, err_func)
+               try:
+                   ALUATargetPortGroup.setup(so_obj, alua_tpg, err_func)
+               except RTSLibALUANotSupported:
+                   pass
 
         # Don't need to create fabric modules
         for index, fm in enumerate(config.get('fabric_modules', [])):

rtslib/target.py

@@ -582,31 +582,43 @@ def _list_mapped_luns(self):
                 if os.path.realpath("%s/%s" % (mlun.path, mlun.alias)) == self.path:
                     yield mlun
 
+
+    # pass through backends will not have setup all the default
+    # ALUA structs in the kernel. If the kernel has been setup,
+    # a user created group or default_tg_pt_gp will be returned.
+    # If the kernel was not properly setup an empty string is
+    # return in alua_tg_pt_gp. Writing to alua_tg_pt_gp will crash
+    # older kernels and will return a -Exyz code in newer ones.
     def _get_alua_tg_pt_gp_name(self):
         self._check_self()
 
+        storage_object = self._get_storage_object()
+        if storage_object.alua_supported is False:
+            return None
+
         path = "%s/alua_tg_pt_gp" % self.path
-        info = fread(path)
-        if info:
+        try:
+            info = fread(path)
+            if not info:
+                return None
             group_line = info.splitlines()[0]
             return group_line.split(':')[1].strip()
-        return None
+        except IOError as e:
+            return None
 
     def _set_alua_tg_pt_gp_name(self, group_name):
         self._check_self()
 
-        path = "%s/alua_tg_pt_gp" % self.path
-
-        info = fread(path)
-        if not info:
-            # pass through backends will not have setup the default
-            # ALUA structs in the kernel.
-            raise RTSLibError("This LUN does not support setting the ALUA Target Port Group")
+        if not self._get_alua_tg_pt_gp_name():
+            return -1
 
+        path = "%s/alua_tg_pt_gp" % self.path
         try:
             fwrite(path, group_name)
         except IOError as e:
-            raise RTSLibError("Cannot set ALUA Target Port Group: %s" % e)
+            return -1
+
+        return 0
 
     # LUN public stuff
 

rtslib/tcm.py

@@ -222,7 +222,15 @@ def _list_alua_tpgs(self):
         '''
         self._check_self()
         for tpg in os.listdir("%s/alua" % self.path):
-            yield ALUATargetPortGroup(self, tpg)
+            if self.alua_supported:
+                yield ALUATargetPortGroup(self, tpg)
+
+    def _get_alua_supported(self):
+        '''
+        Children should override and return false if ALUA setup is not supported.
+        '''
+        self._check_self()
+        return True
 
     # StorageObject public stuff
 
@@ -279,6 +287,8 @@ def is_configured(self):
             doc="Get the list of all LUN objects attached.")
     alua_tpgs = property(_list_alua_tpgs,
             doc="Get list of ALUA Target Port Groups attached.")
+    alua_supported = property(_get_alua_supported,
+            doc="Returns true if ALUA can be setup. False if not supported.")
 
     def dump(self):
         d = super(StorageObject, self).dump()
@@ -408,6 +418,10 @@ def _get_host_id(self):
         self._check_self()
         return int(self._parse_info('Host ID'))
 
+    def _get_alua_supported(self):
+        self._check_self()
+        return False
+
     # PSCSIStorageObject public stuff
 
     wwn = property(StorageObject._get_wwn, _set_wwn,
@@ -427,6 +441,8 @@ def _get_host_id(self):
             doc="Get the SCSI device target id")
     lun = property(_get_lun,
             doc="Get the SCSI device LUN")
+    alua_supported = property(_get_alua_supported,
+            doc="ALUA cannot be setup with rtslib, so False is returned.");
 
     def dump(self):
         d = super(PSCSIStorageObject, self).dump()
@@ -808,10 +824,16 @@ def _get_config(self):
             return None
         return val
 
+    def _get_alua_supported(self):
+        self._check_self()
+        return False
+
     size = property(_get_size,
             doc="Get the size in bytes.")
     config = property(_get_config,
             doc="Get the TCMU config.")
+    alua_supported = property(_get_alua_supported,
+            doc="ALUA cannot be setup with rtslib, so False is returned.");
 
     def dump(self):
         d = super(UserBackedStorageObject, self).dump()

rtslib/utils.py

@@ -37,6 +37,12 @@ class RTSLibError(Exception):
     '''
     pass
 
+class RTSLibALUANotSupported(RTSLibError):
+    '''
+    Backend does not support ALUA.
+    '''
+    pass
+
 class RTSLibBrokenLink(RTSLibError):
     '''
     Broken link in configfs, i.e. missing LUN storage object.