device: Simplify uevent matching in listenToUdevEvents()

This function watches for uvents that match addresses stored in
s.deviceWatchers() and if there's a matching entry signals the associated
channel.

"Matching" in this instance means soem sort of comparison between the
address we're watching for and the sysfs path in the uevent.  Currently we
match any of a bunch of different cases for different types of device.
Being very specific with how we match *sounds* like a good idea, but it's
complicated, tightly coupled to other parts of the code and, ultimately,
pointless.

The user of the data we're collecting here is getDeviceName().  Before
registering a watcher it checks s.sysToDevMap in case the uevent it's
interested in has already happened.

To have consistent behaviour regardless of when the uevent arrives,
the matching that getDeviceName() uses against s.sysToDevMap must be
the same as we use in listenToUdevEvents() and right now, it's not.
So, change the matching in listenToUdevEvents() to be the same as the
much simpler version in getDeviceName().

fixes #848

Signed-off-by: David Gibson <[email protected]>

agent.go

@@ -774,34 +774,14 @@ func (s *sandbox) listenToUdevEvents() {
 
 				fieldLogger.Infof("Got a wait channel for device %s", devAddress)
 
-				// blk driver case
-				if strings.HasPrefix(uEv.DevPath, filepath.Join(rootBusPath, devAddress)) {
-					goto OUT
-				}
-
-				// pmem/nvdimm case
-				if strings.Contains(uEv.DevPath, pfnDevPrefix) && strings.HasSuffix(uEv.DevPath, devAddress) {
-					goto OUT
-				}
-
+				// This is a pretty imperfect way of
+				// matching, but it's the same as we
+				// use in getDeviceName()
 				if strings.Contains(uEv.DevPath, devAddress) {
-					// scsi driver case
-					if strings.HasSuffix(devAddress, scsiBlockSuffix) {
-						goto OUT
-					}
-					// blk-ccw driver case
-					if strings.HasSuffix(devAddress, blkCCWSuffix) {
-						goto OUT
-					}
+					ch <- uEv.DevName
+					close(ch)
+					delete(s.deviceWatchers, devAddress)
 				}
-
-				continue
-
-			OUT:
-				ch <- uEv.DevName
-				close(ch)
-				delete(s.deviceWatchers, devAddress)
-
 			}
 
 			s.Unlock()

device_amd64.go

@@ -16,8 +16,4 @@ const (
 	// processors, thermal zones. Those objects are exported to user space via
 	// sysfs as directories in the subtree under /sys/devices/LNXSYSTM:00
 	acpiDevPath = "/devices/LNXSYSTM"
-
-	// /dev/pmemX devices exported in the ACPI sysfs (/devices/LNXSYSTM) are
-	// in a subdirectory whose prefix is pfn (page frame number).
-	pfnDevPrefix = "/pfn"
 )

device_arm64.go

@@ -15,8 +15,4 @@ const (
 	// processors, thermal zones. Those objects are exported to user space via
 	// sysfs as directories in the subtree under /sys/devices/LNXSYSTM:00
 	acpiDevPath = "/devices/LNXSYSTM"
-
-	// /dev/pmemX devices exported in the ACPI sysfs (/devices/LNXSYSTM) are
-	// in a subdirectory whose prefix is pfn (page frame number).
-	pfnDevPrefix = "/pfn"
 )

device_ppc64le.go

@@ -16,8 +16,4 @@ const (
 	// processors, thermal zones. Those objects are exported to user space via
 	// sysfs as directories in the subtree under /sys/devices/LNXSYSTM:00
 	acpiDevPath = "/devices/LNXSYSTM"
-
-	// /dev/pmemX devices exported in the ACPI sysfs (/devices/LNXSYSTM) are
-	// in a subdirectory whose prefix is pfn (page frame number).
-	pfnDevPrefix = "/pfn"
 )

device_s390x.go

@@ -16,8 +16,4 @@ const (
 	// processors, thermal zones. Those objects are exported to user space via
 	// sysfs as directories in the subtree under /sys/devices/LNXSYSTM:00
 	acpiDevPath = "/devices/LNXSYSTM"
-
-	// /dev/pmemX devices exported in the ACPI sysfs (/devices/LNXSYSTM) are
-	// in a subdirectory whose prefix is pfn (page frame number).
-	pfnDevPrefix = "/pfn"
 )