On Thu, 20 Feb 2014, Vivek Dasmohapatra wrote:

Update: Found an offset for sda11 which does not deadlock:

Deadlocking configurations:

   backing: sda11;  default offset from sda (NOT a multiple of 4 KiB)
   backing: sdb1;   default offset from sdb (!= 4 KiB)
   backing: sda11;  offset from sda is:
                    - a multiple of 4  KiB
                    - a multiple of 4  MiB
                    - a multplie of 16 MiB

Non-deadlocking configurations:

   backing: sdb
   backing: sdb1;   offset from start of sdb is 4096 B
   backing: sda11;  offset from start of sda is 78486397440 B
                    (153293745 sectors)
                    for reference, sda1's offset is 1048576 B (2048 sectors)