Hello, I work on PostgreSQL. I don't use OpenBSD, but recently I've been investigating how fsync() reports write-back errors on all operating systems that people like to run PostgreSQL on:
https://wiki.postgresql.org/wiki/Fsync_Errors It seems to me that on OpenBSD, asynchronous write-back errors might not be reported to userspace in a subsequent call to fsync(), and synchronous write-back errors that are reported to userspace might not be reported in a follow-up call to fsync() (that is, retrying will appear to be successful but in fact your data is gone). Am I wrong? Perhaps some other code elsewhere will record the error at device, filesystem or inode level? I didn't try to test this: I simply compared the brelse() error handling code with that of FreeBSD and NetBSD whose behaviours are known to be correct and incorrect respectively, according to our assessment of what fsync() *should* do. (Or at least the behaviour that PostgreSQL relies on, when it reports that your data exists on disk as part of its checkpoint protocol). OpenBSD certainly appears to be like NetBSD in this respect, so I thought it was worth pinging your list and asking for an expert opinion. Do you think that my suspicion is correct? Would you consider that to be a bug? Thanks! Thomas Munro
