[Bug 1244662] Re: growpart reverses changes because of partx failure

[Scott Moser]

shoot. I thought I had attached a cleaned up version of that.
I tested your newer diff, and i believe it still to be wrong.

My confusion stems from not knowing how partx_{add,del,resize}_partition
functions understand their 'int partno' argument.

Given the partition table layout created by the following input to sfdisk -uS $DEV:
0,0,0
4096,2048,L
0,0,0
2048,2048,L

sfdisk --durmp output shows that as:
$ sudo sfdisk -uS --dump /dev/vdb
# partition table of /dev/vdb
unit: sectors
/dev/vdb1 : start=        0, size=        0, Id= 0
/dev/vdb2 : start=     4096, size=     2048, Id=83
/dev/vdb3 : start=        0, size=        0, Id= 0
/dev/vdb4 : start=     2048, size=     2048, Id=83

There are 2 different numbering schemes being mixed here.
a.) the order of blkid_struct_partlist.parts array as returned by get_partlist
  To my understanding, this is the order as seen in the partition table.
ie:
  vdb2: 1
  vdb4: 0

b.) the "human order" that is input to partx.
  vdb2: 2
  vdb4: 4

The code as it is right now (and with your suggested fix) I believe
makes an invalid assumption about the relationship between A and B.

I'm fairly sure that partx_{add,del,resize}_partition assume 'b' for the
partno parameter.

My fix was to only deal with 'b' in the loop by adding the helper
function that got the partition 'b' with input 'a'. See my cleaned up
patch for example.


** Patch added: "suggested patch"
   https://bugs.launchpad.net/ubuntu/+source/cloud-utils/+bug/1244662/+attachment/3945396/+files/lp1244662-partx-update.diff

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https://bugs.launchpad.net/bugs/1244662

Title:
  growpart reverses changes because of partx failure

Status in “cloud-utils” package in Ubuntu:
  Confirmed
Status in “util-linux” package in Ubuntu:
  Confirmed

Bug description:
  growpart is failing to resize my virtual servers because partx fails
  to reload the partition table:

  root at pierce:~# growpart /dev/vda 3
  failed [pt_update:1] pt_update /dev/vda 3
  partx: /dev/vda: error updating partition 3
  FAILED: pt_resize failed
  ***** WARNING: Resize failed, attempting to revert ******
  Re-reading the partition table ...
  BLKRRPART: Device or resource busy
  The command to re-read the partition table failed.
  Run partprobe(8), kpartx(8) or reboot your system now,
  before using mkfs
  ***** Appears to have gone OK ****

  root at pierce:~# partx --update 3 /dev/vda
  partx: /dev/vda: error updating partition 3

  Apparently it tries to delete the partition, which fails because it's
  in use:

  ioctl(3, BLKPG, {BLKPG_DEL_PARTITION, flags=0, datalen=148, {start=0,
  length=0, pno=3, devname="", volname=""}}) = -1 EBUSY (Device or
  resource busy)

  partprobe doesn't do this, and it works fine, so when I edit
  pt_update() like this:

          #partx --update "$part" "$dev"
          partprobe "$dev"

  ... everything works as expected.

  Version numbers:
  cloud-guest-utils: 0.27-0ubuntu4
  Description:	Ubuntu 13.10
  Release:	13.10

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