Re: [PATCH v2 0/6] Implement a batched fsync option for core.fsyncObjectFiles

On Tue, Sep 07, 2021 at 11:44:52PM -0700, Junio C Hamano wrote:

I doubt that fsyncObjectFiles is something we can reliably test in
CI, either with the new batched thing or with the original "when we
close one, make sure the changes hit the disk platter" approach.  So
I am not sure what conclusion we should draw from such an experiment,
other than "ok, it compiles cleanly."  After all, unless we cause
system crashes, what we thought we have written and close(2) would
be seen by another process that we spawn after that, with or without
sync, no?

Basically yes.  XFS on Linux has shutdown ioctls that allow to simulate
that crash by shutting the file system down which really helps debugging
that kind of code.  A bunch of other file systems (ext4, f2fs) have
also picked this up now (grep for {XFS,EXT4,F2FS}_IOC_SHUTDOWN).