[Bug 1441930] Re: Fix handling of multipathed disks with 4k-sectors

[Mauricio Faria de Oliveira]

Tested on 14.04.3 daily build.

Things go from this:

	~ # df -h /target
	Filesystem                Size      Used Available Use% Mounted on
	/dev/mapper/mpath0p2     31.1G     47.9M     29.4G   0% /target

	~ # cat /proc/swaps
	Filename				Type		Size	Used	Priority
	/dev/mapper/mpath0p3                    partition	1408448	0	-1

	~ # dmsetup table | grep ^mpath0
	mpath0: 0 554287104 multipath 1 queue_if_no_path 1 alua 2 1 round-robin 0 1 1 8:0 1000 round-robin 0 1 1 65:144 1000 
	mpath0p3: 0 2817024 linear 252:0 66468608
	mpath0p2: 0 66466560 linear 252:0 2048
	mpath0p1: 0 1792 linear 252:0 256

To this:

	~ # df -h /target
	Filesystem                Size      Used Available Use% Mounted on
	/dev/mapper/mpath0p2    249.4G     59.1M    236.7G   0% /target

	~ # cat /proc/swaps
	Filename				Type		Size	Used	Priority
	/dev/mapper/mpath0p3                    partition	11268032	0	-1

	~ # dmsetup table | grep ^mpath0
	mpath0-part2: 0 531732480 linear 252:0 16384
	mpath0-part1: 0 14336 linear 252:0 2048
	mpath0: 0 554287104 multipath 1 queue_if_no_path 1 alua 2 1 round-robin 0 1 1 8:0 1000 round-robin 0 1 1 65:144 1000 
	mpath0p3: 0 22536192 linear 252:0 531748864
	mpath0p2: 0 531732480 linear 252:0 16384
	mpath0p1: 0 14336 linear 252:0 2048
	mpath0-part3: 0 22536192 linear 252:0 531748864

        (ignore -part and p separators, this is another bug which should
be backported for as well)

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https://bugs.launchpad.net/bugs/1441930

Title:
  Fix handling of multipathed disks with 4k-sectors

Status in multipath-tools package in Ubuntu:
  Fix Released
Status in parted package in Ubuntu:
  Fix Released
Status in multipath-tools source package in Trusty:
  New
Status in parted source package in Trusty:
  New

Bug description:
  The packages for libparted and kpartx don't have the patches for using
  multipath (actually device-mapper) on 4k-sector disks (generally: 'non
  512-byte sector disks')

  This causes the number of sectors of each device-mapper partition to be 1/8th (512/4096) of that expected.
  These 3 errors were identified:
  1) Partition sizes on multipath are 1/8th of the intended size
  2) The filesystem on the underlying device is not-accessible (only in the dm mapped device)
  3) grub-install fails w/ 'Unknown filesystem'

  The 2 patches attached contains upstream patches from parted and
  multipath-tools, and fix the issues (the installation finishes without
  errors and the system boots).

  
  QEMU/KVM
  --------

  If you don't have 4k-sector disks handy :)

  An example for multipath on 4k-sector disks, with 2 underlying
  devices:

          $ qemu-img create -f raw disk.img 16g

  	$ qemu-system-ppc64 -enable-kvm \
  	  -nographic -nodefaults \
  	  -monitor stdio -serial pty \
  	  -M pseries -m 2G \
  	  -net nic -net user \
  	  -drive media=cdrom,file=../../iso/vivid-server-ppc64el.iso.0408 \
  	  \
  	  -drive file=disk.img,if=none,cache=none,serial=my-serial,id=drive0 \
  	  -drive file=disk.img,if=none,cache=none,serial=my-serial,id=drive1 \
  	  -device scsi-hd,physical_block_size=4096,logical_block_size=4096,drive=drive0 \
  	  -device scsi-hd,physical_block_size=4096,logical_block_size=4096,drive=drive1

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