Hello, I am trying to understand jbd2 checksumming procedure. I reboot ext4 in the middle of a metadata intensive operation using echo b> /proc/sysrq-trigger. I see that the journal gets replayed on next mount using prinks in jbd2/recovery.c: do_one_pass() function. I then corrupt intermediate metadata logged on jbd2 and I still see the journal being replayed without multiple error messages which should ideally get printed when one of the two following flags - JBD2_FEATURE_INCOMPAT_CSUM_V2 or JBD2_FEATURE_INCOMPAT_CSUM_V3 are set. I have 2 questions: 1. Are the two flags: JBD2_FEATURE_INCOMPAT_CSUM_V2 and JBD2_FEATURE_INCOMPAT_CSUM_V3 set by default? If not, how do we set them so that the journal will detect and respond to injected corruptions? 2. this is very naive question, but what do compat and incompat options mean? If flag X in incompat is set, does this mean the feature does not exist? Thank you, -- Shehbaz Jaffer
