xfs: fix unmount hang and memory leak on shutdown during quotaoff
AIL removal of the quotaoff start intent and free of both quotaoff intents is currently limited to the ->iop_committed() handler of the end intent. This executes when the end intent is committed to the on-disk log and marks the completion of the operation. The problem with this is it assumes the success of the operation. If a shutdown or other error occurs during the quotaoff, it's possible for the quotaoff task to exit without removing the start intent from the AIL. This results in an unmount hang as the AIL cannot be emptied. Further, no other codepath frees the intents and so this is also a memory leak vector. First, update the high level quotaoff error path to directly remove and free the quotaoff start intent if it still exists in the AIL at the time of the error. Next, update both of the start and end quotaoff intents with an ->iop_release() callback to properly handle transaction abort. This means that If the quotaoff start transaction aborts, it frees the start intent in the transaction commit path. If the filesystem shuts down before the end transaction allocates, the quotaoff sequence removes and frees the start intent. If the end transaction aborts, it removes the start intent and frees both. This ensures that a shutdown does not result in a hung unmount and that memory is not leaked regardless of when a quotaoff error occurs. Signed-off-by:Brian Foster <bfoster@redhat.com> Reviewed-by: