[PATCH 3 of 5] xend/pvscsi: update sysfs parser for Linux 3.0

[Olaf Hering <olaf@aepfle.de>]

# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1349453226 -7200
# Node ID c18b7d4f0d665d8bc9eb4ff62aad1575088db1a8
# Parent  9f361dc559ddf9e468bbc039584aa8837abdf2bb
xend/pvscsi: update sysfs parser for Linux 3.0

The sysfs parser for /sys/bus/scsi/devices understands only the layout
of kernel version 2.6.16. This looks as follows:

/sys/bus/scsi/devices/1:0:0:0/block:sda is a symlink to /sys/block/sda/
/sys/bus/scsi/devices/1:0:0:0/scsi_generic:sg1 is a symlink to /sys/class/scsi_generic/sg1

Both directories contain a 'dev' file with the major:minor information.
This patch updates the used regex strings to match also the colon to
make it more robust against possible future changes.


In kernel version 3.0 the layout changed:
/sys/bus/scsi/devices/ contains now additional symlinks to directories
such as host1 and target1:0:0. This patch ignores these as they do not
point to the desired scsi devices. They just clutter the devices array.

The directory layout in '1:0:0:0' changed as well, the 'type:name'
notation was replaced with 'type/name' directories:

/sys/bus/scsi/devices/1:0:0:0/block/sda/
/sys/bus/scsi/devices/1:0:0:0/scsi_generic/sg1/

Both directories contain a 'dev' file with the major:minor information.
This patch adds additional code to walk the subdir to find the 'dev'
file to make sure the given subdirectory is really the kernel name.


In addition this patch makes sure devname is not None.

Signed-off-by: Olaf Hering <olaf@aepfle.de>

diff -r 9f361dc559dd -r c18b7d4f0d66 tools/python/xen/util/vscsi_util.py
--- a/tools/python/xen/util/vscsi_util.py
+++ b/tools/python/xen/util/vscsi_util.py
@@ -130,20 +130,36 @@ def _vscsi_get_scsidevices_by_sysfs():
 
     for dirpath, dirnames, files in os.walk(sysfs_mnt + SYSFS_SCSI_PATH):
         for hctl in dirnames:
+            if len(hctl.split(':')) != 4:
+                continue
             paths = os.path.join(dirpath, hctl)
             devname = None
             sg = None
             scsi_id = None
             for f in os.listdir(paths):
                 realpath = os.path.realpath(os.path.join(paths, f))
-                if  re.match('^block', f) or \
-                    re.match('^tape', f) or \
-                    re.match('^scsi_changer', f) or \
-                    re.match('^onstream_tape', f):
+                if  re.match('^block:', f) or \
+                    re.match('^tape:', f) or \
+                    re.match('^scsi_changer:', f) or \
+                    re.match('^onstream_tape:', f):
                     devname = os.path.basename(realpath)
+                elif f == "block" or \
+                     f == "tape" or \
+                     f == "scsi_changer" or \
+                     f == "onstream_tape":
+                    for dir in os.listdir(os.path.join(paths, f)):
+                        if os.path.exists(os.path.join(paths, f, dir, "dev")):
+                            devname = os.path.basename(dir)
 
-                if re.match('^scsi_generic', f):
+                if re.match('^scsi_generic:', f):
                     sg = os.path.basename(realpath)
+                elif f == "scsi_generic":
+                    for dir in os.listdir(os.path.join(paths, f)):
+                        if os.path.exists(os.path.join(paths, f, dir, "dev")):
+                            sg = os.path.basename(dir)
+                if sg:
+                    if devname is None:
+                        devname = sg
                     scsi_id = _vscsi_get_scsiid(sg)
             devices.append([hctl, devname, sg, scsi_id])