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[Colin Ian King <1434183@xxxxxxxxxxxxxxxxxx>]

** Summary changed:

- btrfs: ccompress-force needs clearing when remounting with compress  option
+ btrfs: compress-force needs clearing when remounting with compress  option

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https://bugs.launchpad.net/bugs/1434183

Title:
  btrfs: compress-force needs clearing when remounting with compress
  option

Status in linux package in Ubuntu:
  In Progress

Bug description:
  SRU Justification:  (Trusty, Utopic)

  [Impact]
  Remounting from compress-force to compress could not clear compress-force option. The problem is there is no way for users to clear compress-force option separately. 

  [Fix]
  upstream commit 4027e0f4c4b2df28d564560a3c65c179bebae4c8
  "Btrfs: clear compress-force when remounting with compress option"

  this is a simple one-liner, risk is low to zero.

  [Testcase]
  See attached hacked up bash script.btrfs: Without the fix I can reproduce the oops every time. With the fix, it works perfectly.

  echo "MNT=$MNT"
  echo "TMP=$TMP"

  TMPIMG=$TMP/test.img
  DEV=/dev/loop0

  truncate --size 1500m $TMPIMG
  losetup $DEV $TMPIMG
  mkfs.btrfs -f $DEV
  mount $DEV $MNT -o compress-force=lzo
  mount $DEV $MNT -o remount,compress=zlib
  n=$(cat /proc/mounts | grep $DEV | grep "compress-force=zlib" | wc -l)
  umount $DEV
  losetup -d $DEV
  rm $TMPIMG

  if [ $n -eq 0 ]; then
          echo "compress-force=zlib cleared in remount"
          exit 0
  else
          echo "compress-force=zlib NOT cleared in remount"
          exit 1
  fi

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