[bug] error communication from kernel to userland

[Anand Jain <Anand.Jain@oracle.com>]

Hi,

  the below example tells a problem..

  ----
  # btrfs dev del missing /btrfs
  ERROR: error removing the device 'missing' - Invalid argument

  # dmesg | tail
  ::
  [ 4295.258686] btrfs: unable to go below two devices on raid1
  #
  -----
  as of now the more accurate errors are being logged to dmesg,
  which a normal user might not notice and there are few other
  btrfs cli cases similar to this.

  We need to get the kernel errors to the useland as part the
  cli being used.

  However the btrfs is relaying on the limited set of errno
  defines which is insufficient / inappropriate in the
  btrfs context.

  As a solution we have 2 choices broadly.. as of now

  - Update the errno with more FS and RAID related defines

  - Get the error string as part of ioctl arg.

  - ?


  any comments / questions / views / ideas are welcome..


Thanks, Anand