Re: [PATCH] refs: sync loose refs to disk before committing them

[Neeraj Singh <nksingh85@gmail.com>]

On Thu, Nov 04, 2021 at 02:24:26PM -0700, Junio C Hamano wrote:
> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
> 
> > I think it would probably be best to create a git_fsync_fd() function
> > which is non-fatal and has that config/while loop, and have
> > fsync_or_die() be a "..or die()" wrapper around that, then you could
> > call that git_fsync_fd() here.
> 
> Adding git_fsync_fd() smells like a poor taste, as git_fsync() takes
> an fd already.  How about making the current one into a static helper
> 
> 	-int git_fsync(int fd, enum fsync_action action)
> 	+static int git_fsync_once(int fd, enum fsync_action action)
> 	 ...
> 
> and then hide the looping behavior behind git_fsync() proper?
> 
>         int git_fsync(int fd, enum fsync_action action)
>         {
>                 while (git_fsync_once(fd, action) < 0)
>                         if (errno != EINTR)
>                                 return -1;
>                 return 0;
>         }
> 
> fsync_or_die() can be simplified by getting rid of its loop.
> 
> None of that needs to block Patrick's work, I think.  A version that
> uses raw fsync() and punts on EINTR can graduate first, which makes
> the situation better than the status quo, and all the ongoing work
> that deal with fsync can be extended with an eye to make it also
> usable to replace the fsync() call Patrick's fix adds.

Is there some reason we shouldn't die if writing the ref fails? We are
already accustomed to dying if fsyncing a packfile or the index fails.

I assume the number of refs updated is not that high on any given git
operation, so it's not worth having a batch mode for this eventually.

Thanks,
Neeraj