Red Hat Bugzilla – Bug 592957
libparted returns wrong path for partition
Last modified: 2010-08-12 15:57:20 EDT
Description of problem: I have some scripts which use pyparted to create new partitions on a logical volume. I use the path property of a Partition instance to pass throught to resize2fs. The following works fine on F-12 (pyparted-2.1.2-1.fc12.x86_64): [root@host1 ~]# ipython -nobanner In [1]: import parted In [2]: dev = parted.Device('/dev/vgdata/parted-test') In [3]: dsk = parted.Disk(device=dev) In [4]: dsk.partitions[0].path Out[4]: '/dev/mapper/vgdata-parted--testp1' However, on F-13 (pyparted-3.3-1.fc13.x86_64), the path property returns: [root@host2 ~]# ipython -nobanner In [1]: import parted In [2]: dev = parted.Device('/dev/vgdata/parted-test') In [3]: dsk = parted.Disk(device=dev) In [4]: dsk.partitions[0].path Out[4]: '/dev/dm-10p1' This path doesn't exist. I guess this has something to do with a change in lvm, which now creates symlinks to /dev/dm for logical volumes, but not for partitions on those logical volumes. This is F-13: [root@host2 ~]# ls -l /dev/mapper/vgdata-parted--test* lrwxrwxrwx. 1 root root 8 May 17 14:51 /dev/mapper/vgdata-parted--test -> ../dm-10 brw-rw----. 1 root disk 253, 11 May 17 15:03 /dev/mapper/vgdata-parted--testp1 and this is F-12: [root@host1 ~]# ls -l /dev/mapper/vgdata-parted--test* brw-rw----. 1 root disk 253, 20 2010-05-17 13:44 /dev/mapper/vgdata-parted--test brw-rw----. 1 root disk 253, 21 2010-05-17 13:44 /dev/mapper/vgdata-parted--testp1
This is actually in libparted, which pyparted just calls: libparted/arch/linux.c: /* Check for devfs-style /disc => /partN transformation unconditionally; the system might be using udev with devfs rules, and if not the test is harmless. */ if (!strcmp (dev->path + path_len - 5, "/disc")) { /* replace /disc with /path%d */ strcpy (result, dev->path); snprintf (result + path_len - 5, 16, "/part%d", num); } else if (dev->type == PED_DEVICE_DAC960 || dev->type == PED_DEVICE_CPQARRAY || dev->type == PED_DEVICE_ATARAID || dev->type == PED_DEVICE_DM || isdigit (dev->path[path_len - 1])) snprintf (result, result_len, "%sp%d", dev->path, num); else snprintf (result, result_len, "%s%d", dev->path, num); The "%sp%d" format string is used, but probably should not be used for PED_DEVICE_DM. Reassigning to parted.
Hi Ruben, Normally parted resolves symlinks which causes the behaviour you are seeing. There is a patch in parted to not do this for device mapper devices because of the lvm changes you refer to. But this patch keys of the device path starting with /dev/mapper, from the parted ChangeLog: * Tue Apr 6 2010 Hans de Goede <hdegoede@redhat.com> 2.1-6 - Parted should not canonicalize symlinks under /dev/mapper (#577824) So if you use the symlink under /dev/mapper rather then using the /dev/VgName/LvName one things should work. Please let us know if this resolves your issue. Regards, Hans
Hi Hans, I've changed my scripts now to use the /dev/mapper entries, and this works ok.
Closing per comment #3.