Fix GC hidden attribute in case of SIGTERM signal (#87)

The GC can be interrupted by a SIGTERM signal. If this is caught while modifying
a volume's hidden flag, this can have bad consequences.

For example in the situation below, the hidden flag of a volume has been changed
but the cached value (self.hidden) in the python process still has the old value
because of the 'util.CommandException' exception that was thrown. A VDI
that normally should not be hidden is still hidden after executing
`_undoInterruptedCoalesceLeaf` because the hidden value was not the correct one.

Code:
```
    def _setHidden(self, hidden=True):
        vhdutil.setHidden(self.path, hidden)
        # Exception! Next line is never executed.
        self.hidden = hidden
```

Trace:
```
Jun  5 09:15:50 r620-q6 SMGC: [563219] Removed vhd-parent from dce4b0fc(2.000G/170.336M?)
Jun  5 09:15:50 r620-q6 SMGC: [563219] Removed vhd-blocks from dce4b0fc(2.000G/170.336M?)
Jun  5 09:15:50 r620-q6 SM: [563219] ['/usr/bin/vhd-util', 'set', '--debug', '-n', '/var/run/sr-mount/f816795d-e7a9-43df-170c-23bc329607fc/OLD_dce4b0fc-6ad1-4750-857b-45d8d2758503.vhd', '-f', 'hidden', '-v', '1']
Jun  5 09:15:50 r620-q6 SM: [563219] GC: recieved SIGTERM
Jun  5 09:15:50 r620-q6 SM: [563219] FAILED in util.pread: (rc -15) stdout: '', stderr: ''
Jun  5 09:15:50 r620-q6 SMGC: [563219] *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jun  5 09:15:50 r620-q6 SMGC: [563219]          ***********************
Jun  5 09:15:50 r620-q6 SMGC: [563219]          *  E X C E P T I O N  *
Jun  5 09:15:50 r620-q6 SMGC: [563219]          ***********************
Jun  5 09:15:50 r620-q6 SMGC: [563219] _doCoalesceLeaf: EXCEPTION <class 'util.CommandException'>, Signalled 15
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/cleanup.py", line 2653, in _liveLeafCoalesce
Jun  5 09:15:50 r620-q6 SMGC: [563219]     self._doCoalesceLeaf(vdi)
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/cleanup.py", line 2717, in _doCoalesceLeaf
Jun  5 09:15:50 r620-q6 SMGC: [563219]     vdi._setHidden(True)
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/cleanup.py", line 1063, in _setHidden
Jun  5 09:15:50 r620-q6 SMGC: [563219]     vhdutil.setHidden(self.path, hidden)
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/vhdutil.py", line 235, in setHidden
Jun  5 09:15:50 r620-q6 SMGC: [563219]     ret = ioretry(cmd)
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/vhdutil.py", line 94, in ioretry
Jun  5 09:15:50 r620-q6 SMGC: [563219]     errlist=[errno.EIO, errno.EAGAIN])
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/util.py", line 347, in ioretry
Jun  5 09:15:50 r620-q6 SMGC: [563219]     return f()
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/vhdutil.py", line 93, in <lambda>
Jun  5 09:15:50 r620-q6 SMGC: [563219]     return util.ioretry(lambda: util.pread2(cmd, text=text),
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/util.py", line 255, in pread2
Jun  5 09:15:50 r620-q6 SMGC: [563219]     return pread(cmdlist, quiet=quiet, text=text)
Jun  5 09:15:50 r620-q6 SMGC: [563219]   File "/opt/xensource/sm/util.py", line 217, in pread
Jun  5 09:15:50 r620-q6 SMGC: [563219]     raise CommandException(rc, str(cmdlist), stderr.strip())
Jun  5 09:15:50 r620-q6 SMGC: [563219]
Jun  5 09:15:50 r620-q6 SMGC: [563219] *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jun  5 09:15:50 r620-q6 SMGC: [563219] *** UNDO LEAF-COALESCE
Jun  5 09:15:50 r620-q6 SMGC: [563219] Renaming parent back: dce4b0fc-6ad1-4750-857b-45d8d2758503 -> 056b6f93-66ff-460a-9354-157540b584a8
Jun  5 09:15:50 r620-q6 SMGC: [563219] Renaming /var/run/sr-mount/f816795d-e7a9-43df-170c-23bc329607fc/dce4b0fc-6ad1-4750-857b-45d8d2758503.vhd -> /var/run/sr-mount/f816795d-e7a9-43df-170c-23bc329607fc/056b6f93-66ff-460a-9354-157540b584a8.vhd
Jun  5 09:15:50 r620-q6 SMGC: [563219] Renaming child back to dce4b0fc-6ad1-4750-857b-45d8d2758503
Jun  5 09:15:50 r620-q6 SMGC: [563219] Renaming /var/run/sr-mount/f816795d-e7a9-43df-170c-23bc329607fc/OLD_dce4b0fc-6ad1-4750-857b-45d8d2758503.vhd -> /var/run/sr-mount/f816795d-e7a9-43df-170c-23bc329607fc/dce4b0fc-6ad1-4750-857b-45d8d2758503.vhd
Jun  5 09:15:50 r620-q6 SMGC: [563219] Updating the VDI record
Jun  5 09:15:50 r620-q6 SMGC: [563219] Set vhd-parent = 056b6f93-66ff-460a-9354-157540b584a8 for dce4b0fc(2.000G/8.500K?)
Jun  5 09:15:50 r620-q6 SMGC: [563219] Set vdi_type = vhd for dce4b0fc(2.000G/8.500K?)
Jun  5 09:15:50 r620-q6 SM: [563219] ['/usr/bin/vhd-util', 'set', '--debug', '-n', '/var/run/sr-mount/f816795d-e7a9-43df-170c-23bc329607fc/056b6f93-66ff-460a-9354-157540b584a8.vhd', '-f', 'hidden', '-v', '1']
Jun  5 09:15:50 r620-q6 SM: [563219]   pread SUCCESS
Jun  5 09:15:50 r620-q6 SMGC: [563219] *** leaf-coalesce undo successful
```

Therefore, a VDI impacted by this problem remains hidden and can no longer
be used correctly without manual intervention:
```
Jun  5 09:16:29 r620-q6 SM: [566174] lock: released /var/lock/sm/f816795d-e7a9-43df-170c-23bc329607fc/sr
Jun  5 09:16:29 r620-q6 SM: [566174] ***** generic exception: vdi_clone: EXCEPTION <class 'xs_errors.SROSError'>, Failed to clone VDI [opterr=hidden VDI]
Jun  5 09:16:29 r620-q6 SM: [566174]   File "/opt/xensource/sm/SRCommand.py", line 113, in run
Jun  5 09:16:29 r620-q6 SM: [566174]     return self._run_locked(sr)
Jun  5 09:16:29 r620-q6 SM: [566174]   File "/opt/xensource/sm/SRCommand.py", line 163, in _run_locked
Jun  5 09:16:29 r620-q6 SM: [566174]     rv = self._run(sr, target)
Jun  5 09:16:29 r620-q6 SM: [566174]   File "/opt/xensource/sm/SRCommand.py", line 270, in _run
Jun  5 09:16:29 r620-q6 SM: [566174]     return target.clone(self.params['sr_uuid'], self.vdi_uuid)
Jun  5 09:16:29 r620-q6 SM: [566174]   File "/opt/xensource/sm/FileSR.py", line 704, in clone
Jun  5 09:16:29 r620-q6 SM: [566174]     return self._do_snapshot(sr_uuid, vdi_uuid, VDI.SNAPSHOT_DOUBLE)
Jun  5 09:16:29 r620-q6 SM: [566174]   File "/opt/xensource/sm/FileSR.py", line 754, in _do_snapshot
Jun  5 09:16:29 r620-q6 SM: [566174]     return self._snapshot(snapType, cbtlog, consistency_state)
Jun  5 09:16:29 r620-q6 SM: [566174]   File "/opt/xensource/sm/FileSR.py", line 797, in _snapshot
Jun  5 09:16:29 r620-q6 SM: [566174]     raise xs_errors.XenError('VDIClone', opterr='hidden VDI')
Jun  5 09:16:29 r620-q6 SM: [566174]
```

Signed-off-by: Ronan Abhamon <[email protected]>

Author: Wescoeur

drivers/cleanup.py

@@ -561,7 +561,7 @@ def __init__(self, sr, uuid, raw):
         self.sizeVirt = -1
         self._sizeVHD = -1
         self._sizeAllocated = -1
-        self.hidden = False
+        self._hidden = False
         self.parent = None
         self.children = []
         self._vdiRef = None
@@ -664,15 +664,15 @@ def isCoalesceable(self):
         return not self.scanError and \
                 self.parent and \
                 len(self.parent.children) == 1 and \
-                self.hidden and \
+                self.isHidden() and \
                 len(self.children) > 0
 
     def isLeafCoalesceable(self):
         """A VDI is leaf-coalesceable if it has no siblings and is a leaf"""
         return not self.scanError and \
                 self.parent and \
                 len(self.parent.children) == 1 and \
-                not self.hidden and \
+                not self.isHidden() and \
                 len(self.children) == 0
 
     def canLiveCoalesce(self, speed):
@@ -700,7 +700,7 @@ def getAllPrunable(self):
             # some tapdisks could still be using the file.
             if self.sr.journaler.get(self.JRN_RELINK, self.uuid):
                 return []
-            if not self.scanError and self.hidden:
+            if not self.scanError and self.isHidden():
                 return [self]
             return []
 
@@ -724,7 +724,7 @@ def getAllPrunable(self):
         # Normally we are not in this function when the delete action is
         # executed but in `_liveLeafCoalesce`.
 
-        if not self.scanError and not self.hidden and thisPrunable:
+        if not self.scanError and not self.isHidden() and thisPrunable:
             vdiList.append(self)
         return vdiList
 
@@ -795,7 +795,7 @@ def repair(self, parent) -> None:
     @override
     def __str__(self) -> str:
         strHidden = ""
-        if self.hidden:
+        if self.isHidden():
             strHidden = "*"
         strSizeVirt = "?"
         if self.sizeVirt > 0:
@@ -1055,13 +1055,19 @@ def _setParent(self, parent) -> None:
             Util.log("Failed to update %s with vhd-parent field %s" % \
                      (self.uuid, self.parentUuid))
 
+    def isHidden(self) -> bool:
+        if self._hidden is None:
+            self._loadInfoHidden()
+        return self._hidden
+
     def _loadInfoHidden(self) -> None:
         hidden = vhdutil.getHidden(self.path)
-        self.hidden = (hidden != 0)
+        self._hidden = (hidden != 0)
 
     def _setHidden(self, hidden=True) -> None:
+        self._hidden = None
         vhdutil.setHidden(self.path, hidden)
-        self.hidden = hidden
+        self._hidden = hidden
 
     def _increaseSizeVirt(self, size, atomic=True) -> None:
         """ensure the virtual size of 'self' is at least 'size'. Note that
@@ -1186,7 +1192,7 @@ def load(self, info=None) -> None:
         self.sizeVirt = info.sizeVirt
         self._sizeVHD = info.sizePhys
         self._sizeAllocated = info.sizeAllocated
-        self.hidden = info.hidden
+        self._hidden = info.hidden
         self.scanError = False
         self.path = os.path.join(self.sr.path, "%s%s" % \
                 (self.uuid, vhdutil.FILE_EXTN_VHD))
@@ -1245,7 +1251,7 @@ def load(self, info=None) -> None:
         self.lvActive = info.lvActive
         self.lvOpen = info.lvOpen
         self.lvReadonly = info.lvReadonly
-        self.hidden = info.hidden
+        self._hidden = info.hidden
         self.parentUuid = info.parentUuid
         self.path = os.path.join(self.sr.path, self.fileName)
 
@@ -1379,15 +1385,16 @@ def _loadInfoSizeAllocated(self):
     @override
     def _loadInfoHidden(self) -> None:
         if self.raw:
-            self.hidden = self.sr.lvmCache.getHidden(self.fileName)
+            self._hidden = self.sr.lvmCache.getHidden(self.fileName)
         else:
             VDI._loadInfoHidden(self)
 
     @override
     def _setHidden(self, hidden=True) -> None:
         if self.raw:
+            self._hidden = None
             self.sr.lvmCache.setHidden(self.fileName, hidden)
-            self.hidden = hidden
+            self._hidden = hidden
         else:
             VDI._setHidden(self, hidden)
 
@@ -1397,7 +1404,7 @@ def __str__(self) -> str:
         if self.raw:
             strType = "RAW"
         strHidden = ""
-        if self.hidden:
+        if self.isHidden():
             strHidden = "*"
         strSizeVHD = ""
         if self._sizeVHD > 0:
@@ -1575,7 +1582,7 @@ def load(self, info=None) -> None:
         self._sizeVHD = -1
         self._sizeAllocated = -1
         self.drbd_size = -1
-        self.hidden = info.hidden
+        self._hidden = info.hidden
         self.scanError = False
         self.vdi_type = vhdutil.VDI_TYPE_VHD
 
@@ -1749,10 +1756,11 @@ def _setHidden(self, hidden=True) -> None:
         HIDDEN_TAG = 'hidden'
 
         if self.raw:
+            self._hidden = None
             self.sr._linstor.update_volume_metadata(self.uuid, {
                 HIDDEN_TAG: hidden
             })
-            self.hidden = hidden
+            self._hidden = hidden
         else:
             VDI._setHidden(self, hidden)
 
@@ -3015,9 +3023,9 @@ def _undoInterruptedCoalesceLeaf(self, childUuid, parentUuid):
             child.setConfig(VDI.DB_VDI_TYPE, vhdutil.VDI_TYPE_VHD)
             util.fistpoint.activate("LVHDRT_coaleaf_undo_after_rename2", self.uuid)
 
-        if child.hidden:
+        if child.isHidden():
             child._setHidden(False)
-        if not parent.hidden:
+        if not parent.isHidden():
             parent._setHidden(True)
         self._updateSlavesOnUndoLeafCoalesce(parent, child)
         util.fistpoint.activate("LVHDRT_coaleaf_undo_end", self.uuid)
@@ -3251,9 +3259,9 @@ def _undoInterruptedCoalesceLeaf(self, childUuid, parentUuid):
         parent.deflate()
         child.inflateFully()
         util.fistpoint.activate("LVHDRT_coaleaf_undo_after_deflate", self.uuid)
-        if child.hidden:
+        if child.isHidden():
             child._setHidden(False)
-        if not parent.hidden:
+        if not parent.isHidden():
             parent._setHidden(True)
         if not parent.lvReadonly:
             self.lvmCache.setReadonly(parent.fileName, True)
@@ -3607,9 +3615,9 @@ def _undoInterruptedCoalesceLeaf(self, childUuid, parentUuid):
 
         # TODO: Maybe deflate here.
 
-        if child.hidden:
+        if child.isHidden():
             child._setHidden(False)
-        if not parent.hidden:
+        if not parent.isHidden():
             parent._setHidden(True)
         self._updateSlavesOnUndoLeafCoalesce(parent, child)
         Util.log('*** leaf-coalesce undo successful')