convert password to hash crash, make some user can't login

current HashPasswords run as below
1 check if flag hash = true => end
2 check if flag hash = false
2.1 set flag hash = true in a transaction
2.2 convert password each user per transaction

when has exception at 2.2 password some user don't convert
when re-run by check at 1, remain un-convert user can't convert.
=> some user can't login

solution:
1. remove check at step 1 to run process with un-success user
2. let all task in a transaction

i think 1 is better.