bitkeeper revision 1.1547 (42945455UNorq1ha3va8g7OVydNVmw)

XendDomain.py:
  Improve error handling.
XendCheckpoint.py:
  Switch restore to use os functions to read from the state file.
  Simplify code.
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>

tools/python/xen/xend/XendCheckpoint.py

@@ -23,15 +23,23 @@ PATH_XC_RESTORE = "/usr/libexec/xen/xc_restore"
 sizeof_int = calcsize("i")
 sizeof_unsigned_long = calcsize("L")
 
+def write_exact(fd, buf, errmsg):
+    if os.write(fd, buf) != len(buf):
+        raise XendError(errmsg)
+
+def read_exact(fd, size, errmsg):
+    buf = os.read(fd, size)
+    if len(buf) != size:
+        raise XendError(errmsg)
+    return buf
+
 def save(xd, fd, dominfo):
-    if os.write(fd, SIGNATURE) != len(SIGNATURE):
-        raise XendError("could not write guest state file: signature")
+    write_exact(fd, SIGNATURE, "could not write guest state file: signature")
 
     config = sxp.to_string(dominfo.sxpr())
-    if os.write(fd, pack("!i", len(config))) != sizeof_int:
-        raise XendError("could not write guest state file: config len")
-    if os.write(fd, config) != len(config):
-        raise XendError("could not write guest state file: config")
+    write_exact(fd, pack("!i", len(config)),
+                "could not write guest state file: config len")
+    write_exact(fd, config, "could not write guest state file: config")
 
     cmd = [PATH_XC_SAVE, str(xc.handle()), str(fd),
            dominfo.id]
@@ -72,72 +80,61 @@ def save(xd, fd, dominfo):
     return None
 
 def restore(xd, fd):
-    try:
-        signature = fd.read_exact(len(SIGNATURE),
-            "not a valid guest state file: signature read")
-        if signature != SIGNATURE:
-            raise XendError("not a valid guest state file: found '%s'" %
-                            signature)
-    
-        l = fd.read_exact(sizeof_int,
-                          "not a valid guest state file: config size read")
-        vmconfig_size = unpack("!i", l)[0]
-        vmconfig_buf = fd.read_exact(vmconfig_size,
-            "not a valid guest state file: config read")
-    
-        p = sxp.Parser()
-        p.input(vmconfig_buf)
-        if not p.ready:
-            raise XendError("not a valid guest state file: config parse")
-    
-        vmconfig = p.get_val()
-        dominfo = xd.domain_configure(vmconfig)
-    
-        l = fd.read_exact(sizeof_unsigned_long,
-                          "not a valid guest state file: pfn count read")
-        nr_pfns = unpack("=L", l)[0]   # XXX endianess
-        if nr_pfns > 1024*1024:     # XXX
-            raise XendError(
-                "not a valid guest state file: pfn count out of range")
-    
-        # XXXcl hack: fd.tell will sync up the object and
-        #             underlying file descriptor
-        ignore = fd.tell()
-    
-        cmd = [PATH_XC_RESTORE, str(xc.handle()), str(fd.fileno()),
-               dominfo.id, str(nr_pfns)]
-        log.info("[xc_restore] " + join(cmd))
-        child = xPopen3(cmd, True, -1, [fd.fileno(), xc.handle()])
-        child.tochild.close()
-    
-        lasterr = ""
-        p = select.poll()
-        p.register(child.fromchild.fileno())
-        p.register(child.childerr.fileno())
-        while True:
-            r = p.poll()
-            for (fd, event) in r:
-                if not event & select.POLLIN:
-                    continue
-                if fd == child.childerr.fileno():
-                    l = child.childerr.readline()
-                    log.error(l.rstrip())
-                    lasterr = l.rstrip()
-                if fd == child.fromchild.fileno():
-                    l = child.fromchild.readline()
-                    log.info(l.rstrip())
-            if filter(lambda (fd, event): event & select.POLLHUP, r):
-                break
-    
-        if child.wait() >> 8 == 127:
-            lasterr = "popen %s failed" % PATH_XC_RESTORE
-        if child.wait() != 0:
-            raise XendError("xc_restore failed: %s" % lasterr)
-    
-        return dominfo
+    signature = read_exact(fd, len(SIGNATURE),
+        "not a valid guest state file: signature read")
+    if signature != SIGNATURE:
+        raise XendError("not a valid guest state file: found '%s'" %
+                        signature)
 
-    except IOError, ex:
-        if ex.errno == errno.ENOENT:
-            raise XendError("can't open guest state file %s" % src)
-        else:
-            raise
+    l = read_exact(fd, sizeof_int,
+                   "not a valid guest state file: config size read")
+    vmconfig_size = unpack("!i", l)[0]
+    vmconfig_buf = read_exact(fd, vmconfig_size,
+        "not a valid guest state file: config read")
+
+    p = sxp.Parser()
+    p.input(vmconfig_buf)
+    if not p.ready:
+        raise XendError("not a valid guest state file: config parse")
+
+    vmconfig = p.get_val()
+    dominfo = xd.domain_configure(vmconfig)
+
+    l = read_exact(fd, sizeof_unsigned_long,
+                   "not a valid guest state file: pfn count read")
+    nr_pfns = unpack("=L", l)[0]   # XXX endianess
+    if nr_pfns > 1024*1024:     # XXX
+        raise XendError(
+            "not a valid guest state file: pfn count out of range")
+
+    cmd = [PATH_XC_RESTORE, str(xc.handle()), str(fd),
+           dominfo.id, str(nr_pfns)]
+    log.info("[xc_restore] " + join(cmd))
+    child = xPopen3(cmd, True, -1, [fd, xc.handle()])
+    child.tochild.close()
+
+    lasterr = ""
+    p = select.poll()
+    p.register(child.fromchild.fileno())
+    p.register(child.childerr.fileno())
+    while True:
+        r = p.poll()
+        for (fd, event) in r:
+            if not event & select.POLLIN:
+                continue
+            if fd == child.childerr.fileno():
+                l = child.childerr.readline()
+                log.error(l.rstrip())
+                lasterr = l.rstrip()
+            if fd == child.fromchild.fileno():
+                l = child.fromchild.readline()
+                log.info(l.rstrip())
+        if filter(lambda (fd, event): event & select.POLLHUP, r):
+            break
+
+    if child.wait() >> 8 == 127:
+        lasterr = "popen %s failed" % PATH_XC_RESTORE
+    if child.wait() != 0:
+        raise XendError("xc_restore failed: %s" % lasterr)
+
+    return dominfo

tools/python/xen/xend/XendDomain.py

@@ -5,6 +5,7 @@
  Nothing here is persistent (across reboots).
  Needs to be persistent for one uptime.
 """
+import errno
 import os
 import scheduler
 import sys
@@ -323,16 +324,14 @@ class XendDomain:
         @param progress: output progress if true
         """
 
-        class XendFile(file):
-            def read_exact(self, size, error_msg):
-                buf = self.read(size)
-                if len(buf) != size:
-                    raise XendError(error_msg)
-                return buf
+        try:
+            fd = os.open(src, os.O_RDONLY)
 
-        fd = XendFile(src, 'rb')
+            return XendCheckpoint.restore(self, fd)
 
-        return XendCheckpoint.restore(self, fd)
+        except OSError, ex:
+            raise XendError("can't read guest state file %s: %s" %
+                            (src, ex[1]))
 
     def domain_get(self, id):
         """Get up-to-date info about a domain.
@@ -530,8 +529,9 @@ class XendDomain:
 
             return XendCheckpoint.save(self, fd, dominfo)
 
-        except:
-            raise
+        except OSError, ex:
+            raise XendError("can't write guest state file %s: %s" %
+                            (dst, ex[1]))
 
     def domain_pincpu(self, id, vcpu, cpumap):
         """Set which cpus vcpu can use